Benzene C6H6

Benzene C6H6
Introduction
Benzene is the basic unit of acromatic hydrocarbon, which is composed of six carbons and six hydrogen atoms. It molecular formula is C6H6. The structural formula of banzene shows that each carbon contains one hydrogen atom and two carbon atoms and alternate single and double bond is present between carbon atoms is a ring.
Diagram Coming Soon
Behaviour of Benzene
The chemical analysis and molecular mass determination shows that the molecular formula of benzene is C6H6, which corresponds to alkane (n-hexane) having a molecular formula C6H14. When benzene is treated with chlorine in dark or with KMnO4 solution, no reaction occurs. When the benzene reacts with nitric acid, chlorine and methyl chloride under different conditions then it shows substitution reaction, that is the characteristic property of hydrocarbon.
When benzene reacts with chlorine in presence of sunlight or with Hydrogen in presence of catalyst then addition reaction takes place, that is the characteristics property of unsaturated hydrocarbon.
Benzene As Unsaturated Hydrocarbon
The characteristic reaction of unsaturated hydrocarbon are addition reactions. The following chemical reactions shows the benzene behaves as unsaturated hydrocarbon. In presence of catalyst Nickle when benzene is heated at 150ºC under 10 atm pressure then hydrogenation takes place as a result cyclohexane is formed
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In presence of sunlight when benzene reacts with chlorine at 50ºC under 400 atm pressure then chlorination takes place as a result, hexa cyclo hexane is formed.
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Benzene As Saturated Hydrocarbon
The characteristic reactions of saturated hydrocarbon are substitution reaction. Benzene reacts with different reagents under different conditions and under goes substitution reaction. These reactions show that benzene behaves like a saturated hydrocarbon.
In presence of catalyst concentrated sulphuric acid, when benzene reacts with fuming nitric acid then nitration takes place as a result a substituted product nitro benzene is formed.
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In presence of catalyst Ferric Chloride (FeCl3) when benzene reacts with chlorine then chlorination takes place as a result a substituted product benzene is formed
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In presence of catalyst FeCl3, when benzene reacts with methyl chloride the alkylation takes place as a result methyl benzene or Toluene is formed.
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The above mentioned chemical reaction shows that benzene behaves as a saturated hydrocarbon in spite of a fact that is highly unsaturated hydrocarbon.
Special Character of Benzene
Benzene is not affected by common oxidizing agent such as KMn04 or K2Cr207. Similarly when benzene is treated with chlorine or bromine in dark or with dilute acids no reaction occurs.
However, benzene can easily by oxidized in presence of catalyst Vanadium Pentaoxide (V2O5) to form malcic annydride.
Diagram Coming Soon
Structure of Benzene
Benzene is a basic unit of aeromatic cyclic hydrocarbon which is composed of six carbon and six hydrogen atoms. It molecular formula is C6H6. The structural formula shows that each carbon atom is bonded with one hydrogen atom and two carbon atoms, therefore one free electron is present on each carbon atom which is responsible for the aeromatic character and unusual behaviour of benzene.
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Different scientists explain the unusual behaviour of benzene and proposed several structures, the detail of which is given below.
1. Kekul Structure
In 1865, Kekul proposed the structure of benzene in which six carbon atoms bonded together by an alternate C – C double bond to form a ring structure. This structural formula suggest the addition reaction should perform by benzene. The resonating structure of benzene is equally represented as under:
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The above are equivalent and can result by shifting of double bond, which shows that the position of double bond in benzene ring is not fixed so that all C – H position have a partial double bond character.
2. Dewar Structure
Dewar proposed a structure of benzene in which six carbon atoms are bonded together to form hexagonal planer ring in which each carbon attached with one hydrogen and two carbon atoms combined together to form a pi bond as a result the following three resonating structures are formed..
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3. Armstrong – Bayer Structure
In 1887 Armstrong and in 1892 Bayer proposed Armstrong – Bayer centric formula in which the fourth valency or free electron of each carbon atom is directed towards the center of the molecule, as a result centric density is increased.
Modern Concept of Structure of Benzene
The modern concept of structure of benzene can be explained by the help of following two methods:
1. Atomic Orbital Treatment
2. Rasonance
1. Atomic Orbital Treatment
Benzene is a cyclic hydrocarbon, which is composed of six carbon and six hydrogen atoms, each carbon atom is bonded with one hydrogen and two carbon atoms.
Each carbon atom of benzene is Sp2 hyberdized which contain three equivalent partially fill Sp2 hydrid orbitals and one unhyberdized Pz orbital. The Sp2 bybrid orbitals of each carbon atom are arranged at three corners of triangular planer structure. With an angle of 120ºC.
One Sp2 hybrid orbital of each carbon atom overlapped with S atomic orbital of Hydrogen atom to form a sigma bond between C – H due to the overlapping of Sp2 – S orbitals. The remaining two Sp2 hybrid orbitals of each carbon atom overlapped with Sp2 bybrid of two different carbon atoms to form sigma bond between adjacent C – C due to the linearly overlapping of Sp2 – Sp2 orbital.
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The unhyberdized Pz orbital of each carbon atom is situated perpendicular to the Sp2 plane and parallel to the unhyberidized Pz orbital of other carbon atom. The unhyberdized Pz orbital of two adjacent carbon atoms overlap side by side to form a pi bond between two carbon atoms, therefore three alternate double bonds are formed between carbon atoms in a ring.
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Since the C – C bond lengths in benzene are same i.e. 1.39 Aº, each orbital overlaps with its neighbour equally, therefore all six Pz orbitals overlapped with each other to form a single molecular orbital in such a way an electronic cloud is formed above and below the Sp2 plane (benzene ring) and atrons in benzene is not fixed or they are de localized.
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2. Resonance Or Modern Representation of Structure of Benzene.

Definition
The phenomenon in which position of double bond or pi electroni
1. From Saturated Hydrocarbon
The following two methods show the preparation of benzene from saturated hydrocarbon.
A. From Petroleum or n – Hexane
When n-hexane is heated about 480ºC – 550ºC under 150psi – 300psi pressure and in presence of catalyst such as V2O5 then cyclization takes place as a result cyclo hexame is formed which on dehydrogenation convert into benzene.
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B. From n – Heptane
It presence of catalyst when n-heptane is heated temperature under high pressure then Toluene is formed, which on heating 500ºC – 760ºC in presence of catalyst Co – Mo convert into benzene.
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2. From Unsaturated Hydrocarbon
It presence of catalyst organonickle when ethyne or acetylene is passed throuigh red hot tube then polymerization takes place as a result benzene is formed
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3. From Phenol
When the vapours of Phenol are passed over red-hot zinc dust, then reduction takes place, as a result benzene is formed.
C6H5OH + Zn + C6H6 + ZnO
4. From Sodium Benzene
When sodium benzoate is heated with sodium hydroxide then benzene is formed.
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Reaction of Benzene or Chemical Properties of Benzene
Substitution Reaction of Benzene
Those atoms or molecules or ions, which are electron deficient or contains positive charge are known as electrophile. The chemical reactions in which one electrophile is replaced by another electrophile are called Electrophile Substitution Reaction.
The structure of benzene shows that there is a cloud of pi electrons above and below the plane of benzene molecule. These pi electrons (π) are responsible for electrophile substitution reaction of benzene.
In benzene hydrogen atom act as electrophile. Therefore when any electrophillic reagent reacts with benzene then the hydrogen atom is replaced by attacking molecule to form substituted benzene.
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General Mechanism of Electrophilic Substitution Reactions of Benzene.
The electrophilic substitution reaction in benzene occurs through following mechanism. The π electron which are spread above and below the plane of benzene molecule are responsible for this reaction. An electrophile attacks the pi system of benzene to form a delocalized carbonium ion or sigma complex. The electrophile does this by taking two electrons of Pz orbital to form a sigma bond between it and one carbon atom of benzene ring. This breaks the cyclic system of pi electrons because one carbon becomes Sp3 hyberidized.
This causes instability to the ring, to overcome this instability the benzonium loses a proton from the carbon that bears the electrophile. The loss of proton result in the regeneration of the double bond, which restores the stability of ring and formation of, substituted product.
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Some important electophillic substitution reaction of benzene are given below.
a) Nitration
Introduction of nitro group (NO2)in a compound is called nitration. When benzene reacts with a 1:1 mixture of concentrated nitric acid and concentrated sulphuric acid then nitration takes place as a result nito benzene is formed. In this reaction H2SO4 act as a catalyst.
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b)Sulphonation
Introduction of sulphonic group (HSO3) in a compound is called sulphonation. When benzene reacts with fuming H2SO4 i.e. H2SO4 saturated with SO3, at room temperature then sulphonation takes place as a result benzene sulphonic is formed.
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Various steps of mechanism of sulphonation of benzene are given bwlow
H+HSO4- + SO3 —-> HSO3+ + HSO4-
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c) Halogenation
Introduction of halogen in a compound is called halogenation. In presence of Lewis acid catalyst FeX3, or AlX3, when benzene reacts with halogen than halogenation takes place. As a result halobenzene is formed
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d) Alkylation
Introduction of Alkyle group R in a compound is called alkylation. In presence of catalyst FeX3 or AlX3, when benzene reacts reacts with alkyl halide then alkylation takes place. As result alkyle benzene is formed
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Various steps of mechanism of alkylation are given below.
R+X + FeX3 —-> R+ + FeX4-
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e) Acylation
Introduction of acyl group (R – C = 0) in a compound is called acylation. In presence of catalyst FeX3 or AlX3 when benzene reacts with acyl halide then acylation takes place. As a result, acyl benzene is formed.
Various steps of mechanism of acylation are given below.
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f) Friedal and Crafts Reaction
General chemist friedal and crafts first introduced alkyl group and acyle group in benzene in presence of catalyst FeX3 or AlX3, Therefore, the alkylation and acylation reaction are collectively known as Friedal and Crafts reactions.
2. Addition Reaction of Benzene
Under general circumstances, Benzene under goes addition reaction. As a result of these reactions, the aeromatic character of ring is lost and benzene is reduced to saturated cyclic compound.
Some important addition reactions of benzene are
a) Hydrogenation
Introduction of hydrogen in a compound is called hydrogenation. In presence of catalyst nickle. When benzene is heated at about 150ºC under 10 atm pressure, then hydrogenation takes place. As a result cyclo hexane is formed
C6H6 – 3H2 —-> C6H12 (150ºC, 10 atm, Ni)
b) Halogenation
Introduction of halogen in a compound is called halogenation. In presence of sunlight, when benzene is heated with chlorine at about 50ºC under 400 atm pressure, then halogenation (chlorination) takes place. As a result hexa chloro cyclo hexane is formed.
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3. Oxidation
Benzene do not oxidize by common oxidizing agents such as aqueous alkaline solution of KmnO4 or acidic solution of K2Cr2O7. But in pressure of catalyst Vanadium Pentaoxide (V2O5) benzene is oxidized by oxygen to form a Maleic anhydride.
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Orientation In Benzene
Introduction
Benzene is a basic unit of aeromatic hydrocarbon, which is composed of six carbons and six hydrogen atoms. It molecular formula is C6H6. The structural formula of benzene shows that each carbon contains one hydrogen atom and two carbon atoms and alternate single and double is present between carbon atoms is a ring. Therefore, all carbons atoms and Hydrogen atoms of benzene ring are identical.
Diagram Coming Soon
Explanation
Benzene shows an electrophillic substitution reaction in which one hydrogen atom of benzene is replaced by attacking electrophile E+ as a result, a stable substituted benzene is formed.
C6H6 + E+ —-> C6H5E + H+
In substituted benzene all carbon atoms are not equivalent, therefore the carbon number 1 and 4 are called Para Positions, carbon number 2 and 6 are called Ortho Positions and carbon number 3 and 5 are called Meta Positions.
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1, 4 – Para Positions
2, 6 – Ortho Position
3, 5 – Meta Position
In presence of first substituent E+ the incoming second electrophile Y+ may occupie any of Orth, Para or Meta Position.
Classification of First Substituent Group
Since the incoming second electrophile i.e. Y+ occupie the position as it given by the first electrophile E+. Therefore the first substituent group E+ can be classified into two main groups according to their influence on the reactivity of the ring.
1. Meta Directing Group
2. Ortho Directing Group
1. Meta Directing Group
NO2, HSO3, COOH, COOR, CHO, COR, …. are meta directing group, because they orient or direct the incoming second substituent group Y+ to Meta Position.
Examples
a). Chlorination of Nitro Benzene
In presence of catalyst, FeCl3 when nitro benzene reacts with chlorine then chlorination takes place as a result first Meta chloro nitro benzene and meta dichloro nitro benzene are formed.
C6H5NO2 + Cl2 —-> C6H4NO2Cl + HCl
C6H5NO2 + Cl2 —-> C6H4NO2Cl2 + HCl
b). In presence of catalyst concentrated sulphuric acid, when nitro benzene is heated with nitric acid then nitration takes place, as a result Meta trinitro benzene is formed
C6H5NO2 + NO2OH —-> C6H4(NO2)2 + H2O
C6H4(NO2)2 + NO2OH —-> C6H3(NO2)3 + H2O
c). Nitration of Benzoic Acid
In presence of catalyst concentrated sulphuric acid when benzoic reacts with fuming nitric acid (HNO3), then nitration takes place as a result meta di nitro benzoic acid is formed.
C6H5COOH + NO2OH —-> C6H4NO2COOH + H2O
C6H4NO2COOH + NO2OH —-> C6H3(NO2)2COOH + H2O
2. Ortho Directing Group
X, R, OH, NH2, NR2, NHCOR … are ortho para directing group, because they orient or direct the incoming second substituent group Y+ to ortho para position. As a result a mixture of ortho and para substituted product is formed.
Examples
a). Nitration of Chloro Benzene
In presence of catalyst, concentrated sulphuric acid when chloro benzene reacts with Nitric Acid then Nitration takes place as a result a mixture of ortho nitro chloro benzene and para nitro chloro benzene is formed.
C6H5Cl + NO2OH —-> C6H4CINO2
b). Nitration of Methyl Benzene
In presence of catalyst concentrated sulphuric acid, when methyl benzene or Toluene reacts with nitric acid then nitration takes place, as a result a mixture of ortho nitro toluene and para nitro toluene are formed
C6H5CH3 + NO2OH —-> C6H4CH3NO2

Methane CH4

Methane CH4
Introduction
Organic compounds, which are composed of only carbon and hydrogen atoms are known as hydrocarbons. Those hydrocarbons in which all the valencies of carbon atom are fulfilled by hydrogen atoms are called Saturated Hydrocarbon or alkanes. The first member of alkane family composed of one carbon and four hydrogen atoms and is known as Methane.
Structure of Methane
Methane is a saturated hydrocarbon, which is composed of one carbon and four hydrogen atoms. Its molecular formula is CH4. The structural formula of methane shows that all the valencies of carbon atoms are fulfilled by hydrogen atoms.
The carbon atoms of methane is Sp3 hyberidized which contains four equivalent partially filled Sp3 hybrid orbitals, these bybrid orbitals are arranged at the four corners of regular tetrahedron (tetra hedral structure) with an angle of 109.5º.
The Sp3 hybrid orbitals 1 of carbon atoms overlapp with s atomic orbitals of hydrogen atoms to form a sigma bond between C – H due to the overlapping of Sp3 – S orbitals
Preparation of Methane
Methane can be prepared by the following methods.
1. From Sodium Acetate
When concentrated solution of NaOH reacts with acetic acid then sodium acetate is formed.
CH3COOH + NaOH —-> CH3COONa + H2O
When anhydrous sodium acetate reacts with NaOH then methane is obtained.
CH3OONa + NaOH —-> CH4 + Na2CO3
2. From Methyl Magnesium Iodide
In presence of dry ether when alkyl halide reacts with magnesium metal the Alkyl Magnesium halide is formed. This compound was first synthesized by a German Chemist Grignar, therefore, it is also known as Grignard’s Reagent.
3. From Reduction of Methyl Iodide
Methyl iodide can be reduced to methane by the following methods.
a) By Nascent Hydrogen
When concentrated HCl reacts with powdered zinc metal then nascent Hydrogen is obtained.
2HCl + Zn —-> ZnCl2 + 2[H]
Nascent Hydrogen acts as strong reducing agent. When methyl iodide is reduced with nascent hydrogen then methane is formed.
b) By Catalytic Reduction of Methyl Iodide
In presence of catalyst Palladium (Pd), when methyl iodide reacts with hydrogen then methane is formed
Physical Properties of Methane
1. At ordinary temperature and pressure methane exist as colourless, odourless, non-poisonous gas.
2. Methane gas is less soluble in H2O but easily in organic solvents.
3. Methane molecule is non-polar and symmetric.
4. Methane gas is lighter than air.
Chemical Properties of Methane
Reactivity
Methane is a saturated hydrocarbon which is composed of one carbon and four hydrogen atoms. Its molecular formula is CH4. The structural formula shows that all the valencies of carbon atom are fulfilled by Hydrogen atoms. Therefore, at ordinary temperature and pressure, methane is chemically unreactive. It does not react with any acid, base or oxidizing agent such as KMnO4 or K2Cr2 O7. Under special circumstances methane shows substitution reaction.
Those reactions in which any atoms or molecule is replaced by other atom or molecule is called substitution reaction.
Some important chemical reaction of methane are given below.
1. Halogenation
Introduction of halogen in a compound is called halogenation. In presence of sunlight, when chlorine (halogen) reacts with methane then chlorination (halogenation) takes place as a result hydrogen atom of methane is replaced by chlorine atom to form substituted product monochloro methane or methyl chloride is formed.
CH4 + Cl2 —-> CH3Cl + HCl
In presence of sunlight and excess chlorine further substitution takes place till hydrogen atoms are replaced by chlorine atoms.
CH3Cl + Cl2 —-> CH2Cl2 + HCl
CH2Cl2 + Cl2 —-> CHCl3 + HCl
CHCl3 + Cl2 —-> CCl4 + HCl
Mechanism
The mechanism of chlorination (halogenation) in methane proceeds through the following steps.
First Step
In presence of sunlight chlorine molecule dissociate into two chlorine free radicals.
Second Step
Chlorine fee radical combines with methane molecule to form HCl and methyl free radical.
Third Step
Methyl free radical combines with other chlorine molecule to form a substituted product methyl chloride or monochloro methane and chlorine free radical.
2. Combustion
When methane is heated in presence of air and oxygen then carbondioxide and water are formed with the evolution of large amount of heat energy.
CH4 + 2O2 —-> CO2 + 2H2O -ΔH
3. Cracking Or Pyrolysis
The phenomenon in which large molecules are broken into smaller and simple molecule is called Pyrolysis. When Methane is heated in absence of air or oxygen at about 600ºC then Pyrolysis takes place. As a result carbon black and Hydrogen are formed.
Uses of Methane
1. Methane gas is used as domestic fuel.
2. Methane gas is used in manufacture of methanol, carbon black and polishes etc.

Ethane C2H6

Ethane C2H6
Introduction
Organic compounds which are composed, of only carbon and hydrogen atoms are known as hydrocarbons. Those hydrocarbons in which all the valencies of carbon atom are fulfilled by hydrogen atoms are called Saturated Hydrocarbon or alkenes.
The second member of alkane family composed of two carbon and six hydrogen atoms and is known as Ethane.
Structure of Ethane
Ethane is a saturated hydrocarbon, which is composed of two carbon and six hydrogen atoms. Its molecular formula is C2H6. The structural formula of ethane shows that each carbon contains three hydrogen and single bond is present between two carbon atoms.
H3C – CH3
Each carbon atom of ethane is Sp3 hyberidized which contains four equivalent partially filled Sp3 hybrid orbitals, these hybrid orbitals are arranged at the four corners of regular tetrahedron (tetra hedral structure) with an angle of 109.5º.
Three Sp3 hybrid orbitals of carbon atoms overlap with s atomic orbitals of hydrogen atoms to form a sigma bond between C – H due to the overlapping of Sp3 – S orbitals. The remaining Sp3 hybrid of each carbon atom overlapp with the Sp3 hybrid orbital of other carbon atom to form sigma bond between C – C due to the overlapping of Sp3 – Sp3
Diagram Coming Soon
Preparation of Ethane
Ethane can be prepared by the following methods.
1. From Ethyl Magnesium Iodide
In presence of dry ether when alkyl halide reacts with magnesium metal then Alkyl Magnesium halide is formed. This compound was first synthesized by a German Chemist Grignard, therefore, it is also known as Grignard’s Reagent.
2. From Reduction of Ethyl Iodide
When Zn – Cu couple reacts with ethanol then nascent Hydrogen is obtained.
Zn – Cu + 2C2H5OH —-> (C2H5O)2Zn + Cu + 2[H]
Nascent Hydrogen acts as strong reducing agent. When methyl iodide is reduced with nascent hydrogen then methane is formed.
C2H5l + 2[H] —-> C2H6 – Hl
3. From Hydrogenation of Ethane
Introduction of hydrogen in a compound is called hydrogenation. In presence of catalyst Nickle, Palladium, when ethen is heated with hydrogen at about 250ºC then hydrogenation takes place as a result ethane is obtained.
C2H4 + H2 —-> C2H6
4. By Wurtz Synthesis
When methyl iodide is treated with dry sodium metal, then ethane is formed, in this reaction other products are also formed.
2CH3I + 2Na —-> C2H6 + 2NaI
Physical Properties of Ethane
1. At ordinary temperature and pressure ethane act as colourless gas.
2. Ethane gas is sparingly soluble in water but easily soluble in organic solvents.
3. Ethane gas is lighter then air.
4. The melting point, boiling point and specific gravity of ethane is greater than methane.
Chemical Properties of Ethane
Reactivity
Ethane is a saturated hydrocarbon, which is composed of two carbon and six hydrogen atoms. Its molecular formula is C2H6. The structural formula shows that all the valencies of carbon atoms are fulfilled by hydrogen atoms and single bond is present between two carbon atoms. Therefore, ethane is chemically unreactive. It does not react with any acid, base or oxidizing agents such as KMnO4 or K2Cr2O7. Under special circumstances ethane shows only substitution reaction.
Some important reactions of ethane are given below.
1. Halogenation
Introduction of halogen in a compound is called halogenation. In presence of sunlight when ethane reacts with chlorine (halogen) then chlorination (halogenation) takes place. As a result hydrogen atom of ethane is replaced by chlorine atom to form a substituted product, mono chloro ethane or ethyl chloride.
C2H6 + Cl2 —-> C2H5Cl + HCl
In presence of sunlight and excess chlorine further substitution takes place till all the hydrogen atoms are replaced by chlorine atom.
2. Combustion
When ethane is heated in presence of air or oxygen then carbondioxide and water are formed with the evolution of large amount of heat energy.
C2H6 + 5/2O2 —-> 2CO2 + 3H2O
Uses Of Ethane
Methane is used as fuel.

Ethene C2H4

Ethene C2H4
Introduction
Organic compounds which are composed, of only carbon and hydrogen atoms are known as hydrocarbons. Those hydrocarbons in which all the valencies of carbon atom are not fulfilled by hydrogen atoms and double bonds are present between carbon atoms are called Unsaturated Hydrocarbon or alkenes.
The first member of alkene family composed of two carbon and four hydrogen atoms and is known as Ethene.
Structure of Ethene
Ethene is an unsaturated hydracarbon, which is composed of two carbon and four hydrogen atoms. Its molecular formula is C2H4. The structural formula of ethene shows that each carbon contains two hydrogen and double bond is present two carbon atoms.
H2C = CH2
Each carbon atom of ethene is Sp2 hyberidized which contains three equivalent partially filled Sp2 hybrid orbitals and unhyberidized Pz orbital. The hybrid orbitals are arranged at the three corners of coplaner triangle with an angle of 120º.
Two Sp2 hybrid orbitals of carbon atoms overlapp with s atomic orbitals of hydrogen atoms to form a sigma bond between C – H due to the overlapping of Sp2 – S orbitals. The remaining Sp2 hybrid of each carbon atom overlapp with the Sp2 hybrid orbital of other carbon atom to form sigma bond between C – C due to the overlapping of Sp2 – Sp2.
The unhyberidized Pz orbital of each carbon atom are situated perpendicular to the Sp2 plane and parallel to the unhyberidized Pz orbitals of two different carbon atoms overlap side by side to form a pi bond between carbon atoms.
Diagram Coming Soon
Preparation of Ethene
Ethene can be prepared by the following methods.
1. From Dehydrohalogenation of Ethyl Halide
Removal of hydrogen halide from a compound is called Dehydrogenation. When mono halo ethane or ethyl halide is treated with alcoholic potash (KOH), then dehydrohalogenation takes place as a result ethene is formed.
C2H5X + KOH —-> H2C = CH2 + H2O + KX
C2H5Cl + KOH —-> H2C = CH2 + H2O + KCl
2. From Dehalogenation Of Vicinal Dihalide
Removal of halogen from a compound is called Dehalogenation. Those dihalides in which hydrogen atoms are attached with two adjacent carbon atoms are called Vicinal Dihalide or 1, 2 – dihalo ethane reacts with powdered zinc metal then dehalogenation takes place as a result Ethene is formed.
C2H4X2 + Zn —-> C2H4 + ZnX2
C2H4Cl2 + Zn —-> C2H4 + ZnCl2
3. From Dehydration of Ethyl Alcohol (Ethanol)
Removal of water molecule from a compound is called Dehydration. In presence of catalyst concentrated H2SO4, when ethyl alcohol or ethanol is heated at about 170ºC then Dehydration takes place as a result ethene is formed.
C2H5OH —-> C2H4 + H2O
Dehydration of ethanol can also be called out in following two ways.
1. In presence of catalyst Al2O3 when ethanol is heated at (350 – 360ºC), then ethene is formed
C2H5OH —-> C2H4 + H2O
2. In presence of mixture of Al2O3 and H3PO4 at 250ºC, when ethanol is heated then ethene is formed.
C2H5OH —-> C2H4 + H2O

Alkyl Halide

Alkyl Halide
Introduction
Alkyl halides are the derivatives of alkanes, they are denoted by RX where R may be any alkyl group and X may be any halogen atom (Cl, Br, I). The general formula of alkyl halide is given by
CnH2n + 1 – X
Where n may be any natural number and X may be halogen atom.
Definition
When one hydrogen atom of alkane is replaced by halogen atom then the substituted alkane is formed that is known as alkyl halide or mono halo alkane.
Classification of Alkyl Halide
On the basis of carbon atom alkyl halides are classified into following three classes.
1. Primary Alkyl Halide
2. Secondary Alkyl Halide
3. Tertiary Alkyl Halide
1. Primary Alkyl Halide (Iº RX)
When one hydrogen atom of methyl group is replaced by an alkyl group, then the carbon of the substituted methyl is called Primary carbon atom.
H-CH2- —-> R-CH2-
Those alkyl halides in which halogen atom is attached directly with primary carbon atom are called Primary alkyl halides.
H-CH2-X —-> R-CH2-X
2. Secondary Alkyl Halide (2º RX)
When two hydrogen atoms of methyl group are replace by any alkyl group, then the carbon atom of substituted methyl is called secondary carbon atom.
H2-CH- —-> R2-CH-
Those alkyl halides in which halogen atom is directly attached with the secondary carbon atom are called secondary alkyl halides. The alkyl group may be similar or different.
H2-CH-X —-> R2-CH-X
3. Tertiary Alkyl Halide (3º RX)
When three hydrogen atoms of methyl groups are replaced by any alkyl group, then the carbon atom of the substituted methyl is called Tertiary carbon atom.
H3-C- —-> R3-C-
Those alkyl halides in which halogen atom is attached directly with the tertiary carbon atom are called Tertiary Alkyl Halide. The alkyl group of tertiary alkyl halide may be different or similar.
H3-C-X —-> R3-C-X
Chemical Reactions of Alkyl Halide
Alkyl Halides are highly reactive compounds and show variety of chemical reactions. Some important chemical reactions are given below.
1. SN Reactions
2. Formation of Grignard’s Reagent
3. Elimination Reactions or E-Reactions
1. SN Reactiosn
In alkyl halide, the electronegativity of halogen atoms is greater than carbon atom of alkyl group. Therefore, the shared pair of electron between R – X (C-X) is shifted towards halogen atom. As a result halogen becomes partial negativity charged and carbon atom of alkyl group becomes partial positively charged ion.
+R – X
+H3C – Cl-
Those atoms/molecules/ions, which are electron deficient or contain positive charge are called Electrophile. Those atoms/molecules/ions, which are electron rich or contain negative charge are called Nucleophile.
In alkyl halide, alkyl group act as electrophile where as halogen atom act as nucleophile. Those reactions in which one nucleophile is replaced by other nucleophile are called Nucleophillic Substitution Reactions or simply SN Reactions.
When alkyl halide reacts with attacking nucleophile or nucleophilic reagent then halogen atom of alkyl halide is replaced is replaced by attacking nucleophile to form a substituted product.
R-X + Nu- —-> R – Nu + X
H3C Br + CN —-> H3C – CN + Br-
H3C – Br + OH- —–> H3C – OH + Br-
H3C – Br + SH- —-> H3C – SH + Br-
H3C – Br + NH2- —-> H3C – NH2 + Br-
H3C – Br + OR- —-> H3C – Or + Br-
H3C – Br + -OOCR —-> H3C – OOCR + Br-
To be an affective nucleophile in Sn reaction, the attacking nucleophile should be stronger base than the leaving group.
Classification of SN Reactions
On the basis of Mechanism, SN reactions are classified into following two classes.
1. SN(1) Reactions
2. SN(2) Reactions
1. SN(1) Reactions
Definition
Those nucleophilic substitution reaction in which rate of reaction and formation of product depends upon the concentration of one specie are known as SN(1) Reactions.
Mechanism
The mechanism of SN(1) Reactions proceeds in two steps.
First Step
It is a reversible and slow step, the alkyl halide dissociates into positively charged carbonium ion and negatively charged halide ion (Leaving Group)
Second Step
It is a irreversible and fast step, the attacking nucleophile reacts with the positively charged carbonium to give a final substituted product.
Rate of Reaction
The slow step of a reaction is a rate determining step. In this mechanism, first step is slow and hence is the rate determining step, which shows that the rate of formation of product depends upon the concentration of one molecule i.e. alkyl halide.
Rate of Reaction = K [R - X]
Since the rate of reaction depends upon the concentration of only one molecule, therefore, it is also known as uni-molecular nucleophilic substitution reaction.
Conclusion
In all tertiary alkyl halide, SN reactions proceed through SN(1) mechanism. In all secondary alkyl halides SN reaction may occur through SN(1) mechanism or SN(2) mechanism depending on the nature of the solvent in which the reaction is carried out. Polar solvents help in ionization so they favor SN(1) Reactions.
2. SN(2) Reactions
Definition
Those nucloephillic reactions in which rate of reaction depends upon the concentration of two species is knows as SN(2) Reactions.
Mechanism
The mechanism of SN(2) Reaction occurs through following mechanism.
The attacking nucleophile reacts with carbon atom of alkyl halide to form an intermediate unstable complex, therefore, the formation of C – Nu bond and cleavage of C – X bond occurs simultaneously to form a substituted product and leaving group.
In this mechanism, the attacking nucleophile attacks the carbon atom from opposite side of the halogen atom.
Diagram Coming Soon
Rate pf Reaction
The slow step of reaction is a rate determining step. In this mechanism, the rate of formation of product depends upon the concentration of two species of molecules i.e. alkyl halide and attacking nculeophile.
Rate of Reaction = K [R - X] [Nu-]
Since the rate of reaction depends upon the concentration of two species therefore, it is also known as bimolecular nucleophilic substitution reaction.
Conclusion
In all Primary alkyl halide, SN reactions proceed through SN(2) mechanism. In all secondary alkyl halides SN reaction may occur through SN(1) mechanism or SN(2) mechanism depending on the nature of the solvent in which the reaction is carried out. Polar solvents help in ionization so they favor SN(1) Reactions, where as non polar solvents favours SN(2) mechanism.
Formation of Grignard’s Reagent
In presence of dry ether, when alkyl halide reacts with magnesium metal, then alkyl magnesium halide is formed. This compound was first synthesized by Grignard therefore it is known as Grignard’s reagent.
Grignard’s reagent plays an important role in synthetic organic chemistry because it is used to prepare a variety of organic compounds.
The reaction of Grignard’s reagent are explained on the basis that due to metal, magnesium act as electrophile, therefore the bond between C – Mg is polarized. As a result the carbon atom bonded with magnesium bears a partial negative charge and hence act as nucleophile.
The carbon atom of Grignard’s reagent (nucleophile) reacts with any electrophillic reagent. As a result the bond between C – Mg is broken and a new bond between carbon and electrophillic reagent is formed.
Elimination Reaction Or E-Reaction Or β Elimination Reactions
Definition
Those reactions in which removal of β hydrogen takes place in an alkyl halide with the formation of double bond are known as β – Eliminates Reaction..
OR
Those reactions in which removal of water molecule takes place with the formation of double bond are also called elimination reactions of simply e-reactions.
Reaction Mechanism
Consider alkyl halide which contains two or more than two carbon atoms. The carbon atoms which is directly bonded with halogen atom is called α-carbon atom. The carbon atom (s) adjacent to α-carbon atom is called β – carbon atom and so on.
The hydrogen atom which is directly attached with α – carbon atom are known as α – hydrogen atom. The hydrogen atom which is directly bonded with β – carbon are known as β – hydrogen atom and so on.
In alkyl halide the electro negativity of halogen atom is more than the carbon of alkyl group. As a result the shared pair of electron between C – X is shifted towards Halogen atom. As a result halogen becomes partial positive ion. Now α – carbon pulled the electron of β – carbon and β – carbon pulled the electron of β – hydrogen atom. Therefore, ultimately the positive charge is shifted to β – hydrogen atom.
Thus, the nucleophile or base i.e. OH- attacks β – hydrogen atom. As a result water molecule is formed with the removal of β – hydrogen atom. The bond between α – carbon and β – carbon takes place simultaneously.
Due to the removal of β – hydrogen atom the elimination is also called β – elimination reaction.
Example
When alkyl is heated with alcoholic potash then dehydrohalogenation takes place. As a result, Alkene is formed with elimination of water molecule.
RC2H4X + KOH —-> RHC = CH2 + H2O + KX
Alkene
HC2H4Cl + KOH —-> H2C = CH2 + H2O + KCl
Ethene
Classification of Elimination Reactions
On the basis of mechanism, elimination reactions are classified into the following two classes.
1. E(1) Reaction.
2. E(2) Reaction.
1. E(1) Reaction
Definition
Those elimination reactions in which the rate of reaction depends upon the concentration of one substance or molecule are known as E(1) Reactions.
Mechanism
The mechanism of E1 Reactions occur through following two steps.
First Step
It is a slow and reversible step. Alkyl halide is dissociated into carbonium ion and halide ion.
Second Step
It is a irreversible and fast step, the attacking (OH-) removes a proton (H+) from the β – carbon atom with the simultaneous formation of double bond between α – carbon atom and β – carbon atom.
Rate of Reaction
The slow step of a reaction is rate determining step. In this mechanism the rate of reaction depends upon the first step or on the concentration of only one molecule, i.e. alkyl halide.
Rate of Reaction = K [R - X]
Since the rate of reaction depends upon the concentration of only one substance or molecule, therefore, it is called uni-molecular elimination reaction or simply E(1) Reaction, where 1 stands for uni-molecular.
Conclusion
In all tertiary halides, elimination reaction occurs through E(1) mechanism. In all secondary alkyl halides elimination reaction may occur through both E(1) and E(2) mechanism, which depends upon the nature of the solvent in which the reaction is carried out. The presence of polar solvent favours E(1) mechanism.
2. E(2) Reactions
Definition
Those elimination reactions in which rate of reaction depends upon the concentration of two substances or molecules is known as E(2) Reactions.
Mechanism
The mechanism of E(2) reaction, occur through the following single step. Due to high electronegativity of halogen atom the shared pair of electron between C – X is shifted towards halogen atom. As a result halogen becomes partial negativity charged and α – carbon atom becomes partial positively charged ion. Ultimately, the positive charge is shifted to β – hydrogen to form unstable intermediate transition stage. Immediately the cleavage of C(β) – H and C(α) – H bond takes place simultaneously. As a result double bond is formed between α – carbon atom and β – carbon with the elimination of water molecule.
OH + H3C-CR2+ —-> Transition Stage —-> H2C=CR2 + H2O
Rate of Reaction
The slow step of reaction is a rate determining step. In this mechanism rate of reaction depends upon the concentration of two species, i.e. alkyl halide and base.
Rate of Reaction = K [R - X] [OH-]
Since the rate of reaction depends upon the concentration of two species therefore it is called bimolecular elimination reaction or simply E(2) reaction where 2 stands for bimolecular.
Conclusion
In all primary alkyl halides, elimination reaction occurs through E(2) mechanism. In all secondary alkyl halides elimination reaction may occur through both E(1) and E(2) mechanism, which depends upon the nature of the solvent in which the reaction is carried out. The presence of polar solvent favours E(1) mechanism, whereas non-polar solvent favours E(2) mechanism.

Alcohol ROH

Alcohol ROH
Definition
Organic compounds that contain monovalent functional group OH are called alcohols.
General Formula
Alcohols are denoted by ROH, where R may be any alkyl group. The general formula of aliphatic alcohol is
CnH2n+1 – OH
Where n may be any natural number.
Examples
CH3 – OH | Methyl Alcohol (Methanol)
C2H5 – OH | Ethyl Alcohol (Ethanol)
Classification of Alcohols
On the basis of number of groups, alcohols have been classified into the following.
1. Monohydric Alcohols
2. Dihydric Alcohols
3. Polyhydric Alcohols
1. Monohydric Alcohols (Hydrins)
Those aliphatic compounds that contain only one hydroxyl group (OH) are known as Monohydric Alcohols. They are also known as Hydrins.
Types of Hydrins
On the basis of carbon atom, monohydric alcohols have been further classified into the following.
a. Primary Alcohols
b. Secondary Alcohols
c. Tertiary Alcohols
a. Primary Alcohols
When one hydrogen atom of methyl group is replaced by any alkyl group, then the carbon atom of the substituted methyl is called Primary carbon atom.
H-CH2- —-> R-CH2-
Those monohydric alcohols in which OH group is directly bonded with primary carbon atom are called Primary Alcohols.
H-CH2-OH —-> R-CH2-OH
b. Secondary Alcohols
When two hydrogen atoms of methyl group are replaced by alkyl groups, then the carbon atom of the substituted methyl is called Secondary carbon atom. These alkyl groups may be different or similar.
H-CH2- —-> R2-CH-
Those monohydric alcohols in which OH group is directly bonded with Secondary carbon atom are called Secondary Alcohols.
H-CH2-OH —-> R2-CH-OH
c. Tertiary Alcohols
When three hydrogen atoms of methyl group are replaced by alkyl groups, then the carbon atom of the substituted methyl is called Tertiary carbon atom. These alkyl groups may be different or similar.
H-CH2- —-> R3C-
Those monohydric alcohols in which OH group is directly bonded with Tertiary carbon atom are called Tertiary Alcohols.
H-CH2-OH —-> R3C-OH
2. Dihydric Alcohols
Those aliphatic compounds that contain two hydroxyl group (OH) are known as dihydric alcohols. They are also known as Glycol.
OH-CH2-CH2-OH
3. Polyhydric Alcohols
Those aliphatic compounds that contain three or more hydroxyl group (OH) are known as Polyhydric Alcohols. They are also known as Glycerol.
OH-CH2 -CHOH-CH2-OH
Preparation
Alcohols can be prepared by the following methods.
1. From Alkene
In presence of catalyst, dilute H2SO4, when ethene reacts with water, then ethyl alcohol or ethanol is formed.
C2H4 + H2O —-> C2H5OH
2. From Grignard’s Reagent
The following chemical reaction show the preparation of alcohol from Grignard’s Reagent.
3. From Fermentation
On large scale, ethyl alcohol is produced by fermentation. Fermentation means gentle bubbling or boiling. In presence of microorganism enzymes, one compound is converted into other. Carbondioxide gas is evolved in form of bubbles, therefore the process is called fermentation.
Uses
1. Ethanol is used as a solvent. It dissolves a large variety of organic substances such as gums, resins, tincture and varnishes.
2. It is being extensively used in the form of different beverages.
3. It is used as raw material for the preparation of other organic solvents such as CHCl3, ether and esters.
4. It is used as fuel substitute and for low temperature thermometer.
5. Ethanol is used as inert solvent for certain organic reactions and re-crystallization of many organic compounds.
Classification On The Basis Of Composition
On the basis of composition, alcohols have been classified into following types.
1. Absolute Alcohol
Organic compounds that contain 99.99% pure ethyl alcohol are known as absolute alcohols.
2. Rectified Spirit
Organic compounds that contain 92% – 95% ethyl alcohol are known as rectified spirits.
3. Denatured Alcohol
Organic compounds that contain 85% ethyl alcohol, 11% water and 4% methyl alcohol are known as denatured alcohol. They are also known as methylated spirits.

Aldehyde & Ketone CHO and CO

Aldehyde & Ketone CHO and CO
Definition of Aldehyde
Organic compounds that contain monovalent functional group – CHO are known as aldehydes.
General Formula of Aldehyde
They are denoted by RCHO, where R may be any alkyl group. The general formula for aldehyde is
CnH2n – CHO
Where n may be any natural number.
Structure of Aldehyde
The structural formula of aldehyde shows that it contains a carbonyl group.
Examples of Aldehyde
CH3CHO | Acetaldehyde
HCHO | Formaldehyde
Definition of Ketone
Organic compounds that contain divalent functional group – CO – are called Ketones.
General Formula of Ketone
They are denoted by R may be any alkyl group. The general formula for Ketone is
CnH2n+1 – CO – CnH2n+1
Where n may be any natural number.
Structure of Ketone
The structural formula of ketone shows that it contains a carbonyl group.
Example of Ketone
CH3COCH3 (Acetone)
Preparation of Aldehyde & Ketone
Aldehyde and Ketone can be prepared by the following methods.
1. From Dehydrogenation of Alcohol
Removal of hydrogen from a compound is called dehydrogenation. In presence of catalyst, Cu – Ni couple when alcohol is heated at 180ºC then dehydrohalogenation takes place. As a result, aldehyde and ketone are formed.
H-CH2OH —-> H-CH=O + H2
CH3-CH2OH —-> H-CH=O + H2
(CH3)2-CH-OH —-> (CH3)2-C=O + H2
2. From Oxidation of Alcohol
In presence of oxidizing agents, K2Cr2O7 or concentrated H2SO4, alcohols are oxidized to form aldehyde or ketone.
H-CH2OH + [O] —-> H-CH=O + H2O
CH3-CH2OH + [O] —-> H-CH=O + H2O
(CH3)2-CH-OH + [O] —-> (CH3)2-C=O + H2O
3. From Dry Distillation
By the dry distillation of calsium formate (Calsium salt of formic acid), form aldehyde is obtained.
Ca(COOH)2 —-> HCHO + CaCO3
By the dry distillation of calsium salt of formic acid and calsium salt of carboxylic acid, aldehydes are obtained.
Ca(CH3OOH)2 + Ca(COOH)2 —-> CH3CHO + CaCO3
By the dry distillation of calsium salt of carboxylic acid, Ketone is formed.
Ca(CH3OOH)2 —-> CH3CHO + CaCO3
4. From Ethyne
This method is used for the preparation of acetaldehyde. In presence of catalyst H2SO4 and HgSO4 when ethyne reacts with water than unstable, intermediate vinyle alcohol is formed which on rearrangement of atoms convert into acetaldehyde.
H-C≡C-H + H2O —-> H2C-HCOH —-> H3C-COH
Preparation of Acetone By Pyrolysis of Acetic Acid
In presence of catalyst MnO2, when the acetic acid is heated at about 500ºC then acetone is formed.
CH3COOH —-> CH3-CHO + CO2 + H2O
Uses of Aldehyde
1. Aldehyde is used a preservative for biological specimen, as antiseptic and as disinfectant.
2. It is used in the synthesis of resins and plastics.
3. It is used to prepare drying oils and dyes.
4. It is used in the silvering of mirror.
5. It is used in processing of anti-polio vaccine.
6. It is used to prepare highly explosive cyclonite.
Uses of Ketones
1. It is used as a solvent for organic compounds.
2. It is used for storage of acetylene in solution form.
3. It is used in the preparation of iodoform, chloroform, etc.
4. It is used in the preparation of scent.
5. It is used as nail-polish remover.
6. It is used in the preparation of smokeless gun power and synthetic rubber.

Carboxylic Acid COOH

Carboxylic Acid COOH
Definition
Organic compounds that contain monovalent functional group – COOH are called Ketones.
General Formula
They are denoted by R may be any alkyl group. The general formula for ketone is
CnH2n+1 – COOH
Where n may be any natural number.
Structure
The Structural formula of Carboxylic Acid shows that it contains a carbonyl group.
ROH-C=O
Examples
Acetic Acid (CH3COOH)
Preparation
Carboxylic Acid can be prepared by the following methods.
1. From Grignard’s Reagent
In presence of dry ether and halogen acid when Grignard’s reagent with carbondioxide then Carboxylic Acid is formed.
R-Mg-X + O=C=O —-> COOR-Mg-X —-> RCOOH + MgX2
CH3-Mg-X + 0=C=0 —-> COOCH3-Mg-X —-> CH3COOH + MgX2
2. From Oxidation of Alcohol
In presence of oxidizing agent such as a mixture of K2Cr2O7 and concentrated K2SO4, when primary alcohol is oxidized then aldehyde is form, which on further oxidation convert into Carboxylic Acid.
RCH2-OH —-> RCHO —-> RCOH-O
CH3CH2-OH —-> CH3CHO —-> CH3COH=O
3. From Dehydrogenation of Alcohol
In presence of catalyst Co – Mo couple, when primary alcohol is heated at elevated temperature then aldehyde is formed, which in presence of a mixture of oxidizing agent such as K2Cr2O7 and concentrated H2SO4 convert into Carboxylic Acid.
RCH2-OH —-> RCHO —-> RCOH-O
CH3CH2-OH —-> CH3CHO —-> CH3COH=O
4. From Ethyne
This method is used for the preparation of acetaldehyde. In presence of catalyst H2SO4 and HgSO4 when ethyne reacts with water than unstable, intermediate vinyle alcohol is formed which on rearrangement of atoms convert into acetaldehyde.
H-C≡C-H + H-OH —-> C2H3OH —-> CH3-CHO —-> CH3-COOH
Uses of Carboxylic Acid
1. Carboxylic Acids are used as laboratory reagents.
2. Acetic acid is used as solvent for phosphorus, sulphur, gums and resins.
3. It is widely used in artificial leather production.
4. Acetic acid is used to prepare acetates, esters and cellulose acetate silk.
5. After colouring, it is used as vinegar.

Ester COO

Ester COO
Definition
Organic compounds that contain divalent functional group – COO – are called ester.
General Formula
They are denoted by RCOOR where R may be any alkyl group. The alkyl groups of ester may be similar or different. The general formula of ester is
CnH2n+1 – COO – CnH2n+1
Where n may be any natural number.
Structure
The structural formula of ester shows that it contains a Carbonyl group.
RCOOR
Examples
1. Dimethyl Ester (CH3COOCH3)
Uses of Ester
1. It is used as a good solvent for paints, varnishes, oils, fats, gums, resins, cellulose etc.
2. It is used as plasticizer.
3. It is used in the preparation of artificial flavours and essences.

Ether O

Ether O
Definition
Organic compounds which contain divalent functional group – O – are called ether.
General Formula
They are denoted by ROR where R may be any alkyl group. The alkyl groups of ether may be similar or different. The general formula of ether is
CnH2n+1 – O – CnH2n+1
Where n may be any natural number.
Examples
1. CH3-O-CH3 (DiMethyl Ether)
2. CH3-O-C2H5 (Ethyl Methyl Ether)
Preparation
Ether can be prepared by the following methods.
1. From Ethyl Alcohol
William son prepared diethyl ether from alcohol by using sodium metal or sulphuric acid therefore this method is also William son synthesis.
2. From Ethyl Chloride
When ethyl chloride is heated with dry silver oxide then diethyl ether is formed.
2C2H5Cl + Ag2O —-> C2H5 – O – C2H5 + AgCl
Chemical Properties
Reactivity
Due to greater stability diethyl ether is relatively unreative. When diethyl ether reacts with strong acid such as hydrogen iodide then oxonium ion is formed, which reacts with strong nucleophile and convert into ethyl alcohol and ethyl iodide.
C2H5-O-C2H5 + HI —-> C2H5-OH-C2H5 + I
C2H5-OH-C2H5 + I —-> C2H5-OH + C2H5I
Uses of Ether
1. Ether is used as solvent.
2. It is used as general anaesthetic.
3. Ether is used in the manufacture of smokeless powder.

Phenol

Phenol
Definition
Aeromatic alcohols are called Phenols.
OR
Those derivations of benzene in which hydrogen atom is replaced by OH group are known as Phenol.
Classification of Phenol
On the basis of hydroxyl group (OH) bonded with benzene ring, Phenol are classified into following three classes.
1. Mono Hydric Phenol
2. Di Hydric Phenol
3. Tri Hydric Phenol
1. Mono Hydric Phenol
Those aeromatic phenols which contains only one OH group are called Mono Hydric Phenol.
2. Di Hydric Phenol
Those aeromatic phenols which contain two OH groups are called Di Hydric Phenol.
Diagram Coming Soon
3. Tri Hydric Phenol
Those aeromatic phenols which contain three OH groups are called Tri Hydric Alcohols.
Preparation
Phenol can be prepared by following methods.
1. From Chloro Benzene (Down’s Process)
When chloro benzene is heated with 10% NaOH solution at 300ºC under 200 atm pressure then sodium Phenoxide is formed, which on further heating with HCl convert into Phenol.
Diagram Coming Soon
2. From Benzene Sulphonate
When benzene sulphonate is fused with NaOH at 25ºC ten sodium Phenoxide is formed, which on further heating with HCl convert into Phenol.
Diagram Coming Soon
Physical Properties
1. At ordinary temperature and pressure, phenol exist as colourless, crystalline solid.
2. Phenol has peculiar smell.
3. Phenol is a poisonous compound.
4. The melting point of phenol is 43ºC and its boiling point is 182ºC.
5. Above 68.5ºC Phenol is completely soluble in water.
Chemical Properties
The important chemical reactions of Phenol are
1. Reaction with Sodium Hydroxide (NaOH)
When phenol reacts with NaOH then sodium Phenoxide and water are formed. This reactions shows the acidic nature of phenol.
Diagram Coming Soon
2. Reaction with Zinc Dust
When vapours of phenol are passed through red hot zinc dust then benzene is formed.
Diagram Coming Soon
3. Hydrogenation
Introduction of hydrogen in a compound is called Hydrogenation. In presence of catalyst nickle when phenol is heated with hydrogen at about 150ºC then hydrogenation takes place as a result cyclo hexanol is formed.
Diagram Coming Soon
4. Reaction with Bromine Water
In presence of water, when bromine reacts with phenol then 2, 4, 6 – tri bromo phenol is formed.
Diagram Coming Soon
5. Reaction with Concentrated Nitic Acid
When phenol reacts with concentrated nitric acid then 2, 4, 6 – tri phenol (Picric Acid) is formed.
Diagram Coming Soon
6. Reaction with Dilute Nitric Acid
When Phenol react with dilute nitric acid then a mixture of ortho and Para nitro Phenol is formed.
Diagram Coming Soon
7. Reaction with Sulphuric Acid
When phenol reacts with H2SO4 then ortho phenol sulphonic acid and para phenol sulphonic acid are formed. The amount of product depending upon the temperature, lower pressure i.e. (15 – 20ºC) favours the production of ortho phenol sulphonic acid where as high temperature about 100ºC favours the production of para phenol sulphonic acid.
Diagram Coming Soon
Uses
1. Phenol is uses as antiseptic.
2. Phenol is used in the manufacture of soaps, plastics etc.
3. Phenol is used in the preparation of Picric Acid and Aspirin.
4. It is used as link Preservative.

Polymerization

Polymerization

Definition
The phenomenon in which simple and small molecules are converted into large and complex molecules is known as Polymerization.
The simple and small molecules are known as monomer, where as large and complex molecules are called polymers.
Classification of Polymerization
Polymerization has been classified the following.
1. Addition Polymerization
2. Condensation Polymerization
1. Addition Polymerization
The process of Polymerization in which molecules are added into each other is called Addition Polymerization.
Examples
In presence of traces of oxygen when is heated at about 200ºC under 100 atm pressure, then Polymerization takes place. As a result, monomers add together to form polymer i.e. Polyethene or Polythene.
Diagram Coming Soon
Similarly the Polymerization of Vinyl Chloride to Poly Vinyl Chloride (PVC) and Polymerization of Vinyl Acetate to Poly Vinyl Acetate (PVA) are the examples of Addition Polymerization.
2. Condensation Polymerization
The process of Polymerization in which removal of water molecule takes place with the formation of polymer is called Condensation Polymerization.
Example
Bakelite Plastic is the Polymer that is obtained by the polymerization of Phenol and formaldehyde. During this process removal of water molecule takes place.
Diagram Coming Soon

Cracking Or Pyrolysis

Cracking Or Pyrolysis

Definition
The phenomenon in which large molecules of hydrocarbons are thermally decomposed into smaller molecules in the absence of air or oxygen is known as Cracking or Pyrolysis.
Examples of Cracking
Cracking can be explained with the help of following examples.
1. Methane
When methane is burnt in absence of air then cracking takes place, as a result carbon black and hydrogen are formed.
2. Gasoline
The most important fraction of petroleum is gasoline (petrol) which is used as motor fuel. The fractional distillation of petroleum yields only a small percentage of total petrol demand. The additional quantity of petrol is obtained by the cracking of diesel.
The large less volatile molecules of diesel that have high boiling point are heated in the absence of air using a catalyst. As a result, cracking takes place and smaller more volatile molecules of petrol having lower boiling point are obtained.
Thus cracking is applied to obtain additional amount of gasoline from crude oil. In cracking a number of other useful by products are also obtained

Detergent

Detergent 

Definition
Detergents are the salts of alkyl sulphate or aryl sulphate that improves the cleaning action of solvents, particularly ionic solvents.
Explaination
Detergents are long chain molecules, which when dissolve in water dissociate into positive and negative ions, these ions react with the ions of dirt and grease to produce soluble compounds with are readily carried away by the water molecules.
General Formula
Detergents are sodium or potassium salts of alkyl sulphate or aryl sulphate.
R-OSO3-Na+ Sodium Alkyl Sulphate
Where R is an alkyl group containing 7 to 18 carbon atoms. Soaps are sodium or potassium salts of long chain fatty acids.
R – COO-Na+
Composition of Detergents
Detergents are composed of two main parts namely.
1. Hydrophobic Part
2. Hydrophilic Part
1. Hydrophobic Part
It is a water repelling part of detergent, which consist of long hydrocarbon chain. The hydrocarbon chain being non-polar attracts dirt particles, which are normally non polar, i.e. greasy or oily molecules. Therefore, this part of detergent removes dirt particles from thing being washed and water takes away the dirt particles with it.
2. Hydrophilic Part
Hydrophilic part of the detergent is water attracting part. It consists of small ionic groups such as sulphonate (SO3) and sulphate (-SO3-). The hydrophilic group being ionic gets attracted by the polar water molecules and in this way, this part of the detergent removes the ionic dirt particles.
Advantage of Detergents
Detergents can act in hard water, since the calsium and magnesium salts of detergents are soluble in water. Whereas, the corresponding salts of soap are insoluble in water. Thus detergents are better cleaning agents than soaps.
Disadvantages of Detergents
One disadvantage of detergent over soap is that hydrocarbon chain, unlike those of soaps, which are derived from food substances (fats and oil) cannot be broken down by bacteria and dispersads. Therefore, it causes water pollution.

Isomerism

Isomerism

Definition
The phenomenon in which different compounds have the same molecular formula but different structural formula or electronic configuration is known as Isomerism.
The different compounds are called Isomers.
Types of Isomerism
There are various types of isomerism, but the four important types are
1. Chain Isomerism
2. Position Isomerism
3. Functional group Isomerism
4. Metamerism
1 Chain Isomerism
The phenomenon in which different compounds have the same molecular formula but differ in length of carbon chain is called Chain Isomerism. The structures are known as Chain Isomers.
Examples
1. Methane, Ethane and Propane have no chain isomers because the cannot be rearranged with small carbon chain.
CH4 CH3-CH3 CH3-CH2-CH3
2. The carbon chain of butane (C4H10) is long enough. So, butane has two isomers.
CH3-CH2-CH2-CH3 (n-butane)
CH3-CHCH3-CH3 (iso-butane)
3. Pentane (C5H12) shows the following isomers.
CH3-CH2-CH2-CH2-CH3 (N-PENTANE)
CH3-CHCH3-CH2-CH3 (ISO-PENTANE)
In saturated hydrocarbons, the number of isomers increase with increase in number of carbon atoms. This is the reason why decane shows 75 isomers.
2. Position Isomerism
The phenomenon in which different compounds have same molecular formula but differ in position of functional group, double bond or triple bond in same length of carbon chain is called Position Isomerism. The structures are called Position Isomers.
Examples
1. Propyl alcohol shows two position isomers.
Diagram Coming Soon
2. Butene C4H8 has two position isomers.
Diagram Coming Soon
3. Functional Group Isomerism
The phenomenon in which different compounds have same molecular formula but differ in functional groups is called functional group Isomerism. The structures are known as functional group isomers.
4. Metamerism
The phenomenon in which different compounds have same molecular formula and functional group but different alkyl groups attached to the same multivalent atom is called metamerism.

Paints

Paints
Definition
Paints are fluids that are applied on a surface to form a hard continuous film on it for protection or decoration.
Wooden and metallic articles are coated with paints to decorate them as well as to protect from corrosion or rusting.
Composition of Paints
Paints are usually composed of three components.
1. Pigments
2. Binders
3. Volatile Solvent
To make a paint, a suitable solvent is used in which both the binder and the pigment are dissolved.
1. Pigments
The pigment of paint gives it colour, it also gives hardness and bulk. Common pigments are titanium dioxide – TiO2 (white), Iron oxide – Fe2O3 (brown or red), Carbon Black – C (black), Chrome Yellow – PbCrO4 (yellow) and organic dyes of various colours.
2. Binders
The binder or vehicle is the part of the paint that carries the pigment particles and hold the entire film of the paint on the surface. Generally some plant oils such as linseed oil, natural and synthetic resin (liquid plastics) are used as binders.
3. Volatile Solvents
To make paint a suitable solvent is selected in which both the pigment and binder are dissolved. The solvent evaporates after the paint is applied. Solvent does not effect the quality of dry paint. Commonly, water or turpentine is used as solvent.
Classification of Paints
On the basis of nature of solvent, the paints are classified into the following two classes.
1. Oil Based Paints
2. Water Based Paints
1. Oil Based Paints
In these paints turpentine is used as solvent. Turpentine is a liquid mixture of hydrocarbon that is obtained from pine trees.
2. Water Based Paints
In these paints, water is used as solvent. Both binders and pigments form a suspension in water.

Varnish

Varnish is a mixture of resin, volatile organic solvents and drying oils. To prepare Varnish such as resin (plastic in liquid state) is dissolved in volatile organic solvents, such as ether or alcohol and then drying oil such as linseed oil is added to it.
The drying oils such as linseed oil consist of esters of highly unsaturated acids containing two or more double bonds. When exposed to air, these oils absorb oxygen and form hard and tough film. The film is insoluble in water.
When a Varnish is applied to the surface, the volatile organic solvents evaporate quickly and the drying oil absorbs oxygen and a hard tough glossy film is obtained. The glossy appearance of the film is due to the presence of resin. Varnish differ from paints in such a manner that, it does not has any added pigment.

Fertilizers

Fertilizers

Definition
Fertilizers are the water soluble substances which provide one or nutrient materials to the soil essential for the nourishment of plants.
Explanation
Fertilizers are water-soluble salts that are absorbed by the plants through osmosis process. Fertilizers are mostly inorganic salts containing nitrogen phosphorus or potassium etc. these elements are essential for the growth and development of plants. Those nutrient materials which plant needs in large quantities are called Macro Nutrients. Those nutrient elements which plant need in small quantities are called Micro Nutrients.
Functions of Fertilizers
The main functions of fertilizers are
1. It helps the soil to make up the deficiency of nutrient element and becomes fertile again.
2. The main function of fertilizers is to maintain the pH of soil to neutrality (7 – or slightly alkalinity (10).
Types of Fertilizers
Fertilizers have been classified into the following types.
1. Natural Fertilizers
2. Artificial Fertilizers
1. Natural Fertilizers
Natural Fertilizers are also known as organic fertilizers. The main source of natural fertilizers is the excretory product of animals and decade product of plants.
2. Artificial Fertilizers
Artificial Fertilizers are also known as synthetic fertilizers and mineral fertilizers. They are obtained from raw mineral materials.
Artificial fertilizers have been further classified into
a. Nitrogenous Fertilizer
In these fertilizers, nitrogen is present as the essential element.
Example
Ammonium Nitrate – NH4NO3
Ammonium Sulphate – (NH4)2SO4
b. Potassic Fertilizer
In these fertilizers, Potassium is present as the essential element.
Example
Chilli Salt Peter – KNO3
c. Phosphatic Fertilizer
In these fertilizers, phosphate is present as the essential element. Phosphatic fertilizers are further classified into following.
i. Super Phosphate
The raw material of super phosphate fertilizer is phosphorite. The molecular formula of Phosphorite is [Ca3(PO4)2]3 CaF2. This rock reacts with sulphuric acid and converts into water soluble super phosphate.
Ca3(PO4)2 + 2H2SO4 —-> Ca(H2PO4)2 + 2CaSO4
The mixture of calsium dihydrogen phosphate and gypsum is called super phosphate.
ii. Triple Phosphate
This phosphate fertilizer is obtained by the decomposition of phosphate rock or phosphorite with phosphoric acid.
Ca3(PO4)2 + 4H3PO4 —-> 3Ca(H2PO4)2

Plastic

Plastic

Definition
Plastics are macromolecules, which are formed by the polymerization of simple molecules.
Explanation
In other words we can say that plastic are the polymers formed from monomers. The phenomenon in which simple and smaller molecules are combined together to form complex and large molecules, is called polymerization. The simple and smaller molecules are called monomers and the large and complex molecules are called polymers.
Types of Plastic
There are the following two types of plastics.
1. Thermo Plastic
2. Thermosetting Plastic
1. Thermo Plastic
Thermo plastic is also known as Thermo-softening plastic. This type of plastic is manufactured by heating, softening melding and cooling the raw materials, this process can be repeated and it does not effect the properties of plastic.
2. Thermosetting Plastic
Thermosetting plastics are those materials, which cannot be heated, only once before they set, i.e. they cannot be reworked.
Examples of Plastic
1. Polyethene (Polythene)
In presence of traces of oxygen, when ethene is heated at 200ºC, under 100 atm pressure then polymerization takes place. As a result, polyethene is formed, which is commonly known as polythene.
Diagram Coming Soon
Uses
Polythene is the most common plastic used to form polythene bags and to package food.
2. Poly Vinyl Chloride (PVC)
PVC or Poly Vinyl Chloride is the polymer of vinyl chloride. When vinyl chloride is heated at 80ºC in the presence of catalyst hydrogen peroxide, then polymerization takes place. As a result, Poly Vinyl Chloride is formed.
Uses
PVC is used for insulating covering for electrical cables, for the manufacture of gramophone, records, suitcase covering etc.
3. Poly Vinyl Acetate (PVA)
Poly Vinyl Acetate (PVA) is the polymer of vinyl acetate.
Uses
PVA is used in the manufacture of chewing gums and in the water proofing of textiles.
4. Bakelite
Bakelite is a polymer of phenol and formaldehyde. By the condensation of two molecules of phenol with formaldehyde, a polymer Bakelite is obtained.
Diagram Coming Soon
Uses
Bakelite is used to make buttons, switches, electrical boards, camera, radio, telephone etc.
Quality of Plastics
During the polymerization, some other components are also mixed to improve the quality of the plastic. For example, plasticizer is mixed with the polymer. It reduces the brittleness and improves the elasticity of plastic. Fillers are also mixed with the polymer, which usually increases the mechanical strength of plastics, Some pigments or dyes are added to get various coloured plastics.
Plastic Industry of Pakistan
The plastic industry in Pakistan essentially consists of moulding of plastic powders into various articles of daily use.

Glass

Glass

Definition
Glass is a hard material that is usually transparent made by cooling certain molten materials in such a manner that they do not crystallize but remain in amorphous state.
Glass is considered to be a super cooled liquid, i.e. the solid in which the molecules are present as aggregates as in liquid, and are not present in any definite pattern.
Preparation of Glass
The principle ingredients of all types of glass are sand or silica (SiO2). Therefore, glass is one of the most important artificial silicates. For example, the ordinary soft glass or Soda Glass is a mixture of Sodium Silicate (Na2SiO3) and Calsium Silicate (CaSiO3).
Soda glass is manufactured by heating sand (SiO2), sodium carbonate (Na2CO3) and calsium carbonate (CaCO3) in a furnace at high temperature, i.e. 1400ºC
Types of Glass
Glass is classified in a number of ways on the basis of its chemical composition, properties, manufacturing process or it’s use. Some important types of glass are as follows.
1. Soft Glass or Soda Glass
Soft glass or Soda glass is an ordinary glass which is a mixture of sodium silicate and sodium calcium silicate. it is also known as window glass.
2. Refractory Potassium Glass
It is a mixture of potassium silicate and calcium silicate. It has high refractive index. This glass is used for making prism, lenses and decorative glass wear.
3. Pyrex Glass
It is boro silicated glass. The main constituents of Pyrex Glass are boroxide (B2O3) and silica (SiO2). This glass has no chemical durability and is soluble even in water.
4. Water Glass
Water glass is just a sodium silicate, which is prepared by the reaction of sodium oxide (Na2O) and silica (SiO2). This glass has no chemical durability and is soluble even in water.
5. Coloured Glass
Coloured glass is prepared by adding certain transition metal oxides. For example copper oxide (CuO) gives light blue coloured glass, where as cobalt oxide (CoO) gives dark blue colour, chromium oxide (Cr2O3) gives green colour and zinc oxide (ZnO) give red coloured glass.
6. Photochromic Glass or Photosensitive Glass
Photochromic glass produces darkness on exposure to bright sunlight but becomes clear again in absence of light. This glass contains silver chloride or silver bromide salts which is sensitive to light, in presence of light, the salt is decomposed to give finely divided black silver, in absence of sunlight, silver and chloride recombine to reform AgCl. This glass is used in sunglasses.
7. Optical Fibres
Optical fibres are thin fibres of silica glass of high purity. They have excellent optical transparency. This glass is used to transmit T.V Programs, Telephone conversion, Computer output etc. It is also used to make a design on glass. This process is called Etching

Silvering Of Mirror

Silvering Of Mirror
Mirror
A mirror is a glass plate coated with silver film on one side.
Silvering of Mirror
Coating a glass plate with silver is called silvering of mirror.
Explanation
When ammonical silver nitrate solution is treated with an aldehyde or other organic reducing agent on the surface of a glass plate the silver (I) is reduced to silver (0). This metallic silver is deposited on the glass plate as a fine film.
The chemical reactions that occur are as follows.
AgNO3 + 2NH4OH —-> [Ag(NH3)2]+ + NO3- + 2H2O
[Ag(NH3)2]+ + RCHO + H2O —-> Ag0↓ + RCOOH + 2NH4+
Method
The process of silvering of mirror is carried out through the following steps.
1. A solution of silver nitrate and ammonia is prepared in distilled water.
2. The aqueous solution of ammonia is slowly added to the solution of silver nitrate until brown precipitates of silver oxide form and dissolve.
3. The mixture is ammonical silver nitrate solution. This solution is mixed with a solution of an organic reducing agent such as glucose.
4. After mixing all the compounds thoroughly, the solution is poured on to the centre of a clean glass surface.
5. The reaction immediately starts and thin film metallic silver deposited on the surface of the glass.
6. The silver film is then coated with either shellae of copal varnish. Finally it is painted with some colour, normally red.
Spraying Method
Silvering of mirror can also be carried out by spraying method. In this technique, the mixture of chemicals is sprayed onto the glass sheet.

Bleaching Powder

Bleaching Powder

Definition
Bleaching powder is a white amorphous powder with smell of chlorine.
Formula of Bleaching Powder
On the basis of available percentage of chlorine, the formula of bleaching powder was suggested by Professor Odling. The formula is given by
Ca(OCl)Cl or CaOCl2
Preparation of Bleaching Powder
Bleaching powder is prepared on the large scale by Hasen Clever Process. The plant consist of a number of iron cylinders in which chlorine is brought in contact with slaked lime [Ca (OH)2].
Ca(OH)2 + Cl2 —-> CaOCl2 + H2O
Chemical Reactions of Bleaching Powder
1. In aqueous solution bleaching powder liberates chlorine.
CaOCl2 + H2O —-> Ca(OH)2 + Cl2
2. It reacts with acids to set free chlorine.
CaOCl2 + 2HCl —-> CaCl2 + H2O + Cl2
3. It reacts with atmospheric CO2 and moisture to give following reaction.
2CaOCl2 + CO2 + H2O —-> CaCO3 + CaCl2 + 2HOCl
Uses of Bleaching Powder
1. It is used for sterilization of drinking water.
2. It is used for bleaching of cotton, linen and paper pulp.
3. It is used for the preparation of Cl2 gas and chloroform (CHCl3).

Corrosion

Corrosion

Definition
Corrosion is the deterioration of a metal, as a result of its reactions with the environment or any chemical agent.
It is an oxidation process that occurs at the surface of the metal.
Causes of Corrosion
Corrosion may be regarded as the natural tendency of metals to return to their oxidized state. The main causes of corrosion are as follows.
1. The atomosphere
2. Submersion in water
3. Underground Soil Attack
4. Emersion in chemicals
5. Corrosive gases
The most important of these is the atmosphere.
Examples of Corrosion
Some familiar examples of corrosion are as follows.
1. Rusting of Iron
2. Detarnishing of silver
3. Development of green coating on copper, brass and bronze.
Types of Corrosion
There are two types of corrosion.
1. Atmospheric Corrosion
When corrosion in metal is due to the action of atmosphere, it is known as atmospheric corrosion.
2. Corrosion in Liquid
When corrosion in metal is due to the reaction of a liquid on a metal, it is known as corrosion in liquid.
Rate of Corrosion
Corrosion is a chemical process. Different metals corrode at different rates. Gold does not corrode at all. Iron corrodes slowly. Tin, lead, copper and silver corrode very slowly.
Prevention From Corrosion
Corrosion causes great damages to metallic articles such as bridges, ships and vehicles. It has been found out that due to corrosion, one fifth of iron is lost annually. Therefore, any one of the following methods are adopted to prevent corrosion.
1. Protective Metallic Coating
In this method, the metal is coated with a thin layer of less oxidizing metal, which reduces the rate of corrosion. For example, corrosion of iron is prevented by coating it with zinc, tin or chromium.
2. Non-Metallic Material Coating
In this method, the metal is coated with a thin layer of non metallic material such as paints, oils, grease, plastic emulsion, enamels etc. For example, red lead (Pb3O4) and zinc chromate (ZnCrO4) are often used for this purpose.
3. Alloying of Metals
Metals can be made more reistant against corrosion by making their alloys. For example, stainless steal is an alloy of Fe, Cr and Ni.
4. Electro-Plating
Noble and bare metals are used for Electro-Plating on any desired metal.

Varnish

Varnish is a mixture of resin, volatile organic solvents and drying oils. To prepare Varnish such as resin (plastic in liquid state) is dissolved in volatile organic solvents, such as ether or alcohol and then drying oil such as linseed oil is added to it.
The drying oils such as linseed oil consist of esters of highly unsaturated acids containing two or more double bonds. When exposed to air, these oils absorb oxygen and form hard and tough film. The film is insoluble in water.
When a Varnish is applied to the surface, the volatile organic solvents evaporate quickly and the drying oil absorbs oxygen and a hard tough glossy film is obtained. The glossy appearance of the film is due to the presence of resin. Varnish differ from paints in such a manner that, it does not has any added pigment.

Tin Plating 

Definition
The art of coating a metal with tin is called Tin-Plating.
Those metals which are coated with tin are called tin-plated metals.
Purpose And Examples of Tin Plating
The purpose of tin plating is to protect metals from corrosion and food poisoning. Iron is often tin-plated to protect it from rusting. The common cooking oil containers are made of tin-plated iron. The household utensils of copper and brass are tarnished in moist air due to the formation of thin layer of oxides and carbonates of copper. These are poisonous, due to these problems, utensils are coated with tin.
Method of Tin Plating
Tin plating is carried out by the following methods.
1. Hot Dipping or Mechanical Method
In this method, clean iron or steel sheets are dipped in the bath of molten tin. A layer of tin accumulates on the iron sheet and it gets coated.
2. Electrolytic Method or Electro-Plating
This method is based on electrolytic process. An electrolytic cell is developed, which contains metals to be tin-plated as cathode and pure tin as anode. The electrolytic solution consists of salt of tin such as tin chloride or tin sulphate and an acid such as hydrochloric acid. On passing electric current through the electrolytic cell tin deposits on the metal sheet. Through this method a uniform layer of tin is coated on zinc.
3. Classical Method
In this method, the clean hot surface of a utensil is polished with tin metal with a rag. Copper and Brass utensils are tin-plated by this method. The utensils are heated and rubbed with ammonium chloride before they are tin plated. This is done to remove the oxide from the utensils.

Pigments

Pigments

Definition
Pigments are the substances which are used to give the proper colour to paints.
Types of Pigments
Lead forms various types of pigments. Some of them are given below.
1. White lead Pigment
2. Red lead Pigment
3. Chrome Yellow Pigment
4. Chrome Red Pigment
5. Turner’s Yellow Pigment
1. White Lead Pigment
White lead Pigment is a basic lead carbonate.
Molecular Formula
[2PbCO3. Pb(OH)2] or [Pb3(OH)2.(CO3)2]
Colour
This lead pigment is white in colour.
Properties
The white colour gradually darken due to the formation of Pbs with Atmospheric H2S. It is also poisonous.
2. Red Lead Pigment (Sandhur)
Molecular Formula
Pb3O4 – Triplumbic Tetra Oxide
2PbO.PbO2 – Lead-Sesqui Oxide
Colour
It is used as red coloured pigment, which varies from orange red to brick red dur to particle size and impurities.
Properties
It is soluble in water but soluble in acids.
3. Chrome Yellow Pigment
Molecular Formula
PbCrO4 – Lead Chromate
It occurs in nature as crocoite.
Colour
It is used as yellow coloured pigment.
Properties
It is insoluble in water but soluble in nitric acid and caustic alkalis.
4. Chrome Red Pigment
Molecular Formula
PbCrO4.PbO – Basic Lead Chromate
Pb2CrO5 – Basic Lead Chromate
Colour
It is used as dark red pigment in paints.
5. Truner’s Yellow Pigment
Molecular Formula
PbCl2.4PbO
Other Pigments
Except above pigments, yellow lead monoxide (massicot) and red lead monoxide (litharge or Murda-sang) are also used in paints.