CARBON COMPOUNDS .

CARBON COMPOUNDS

INTRODUCTIONCarbon compounds large number compounds with hydrogen called hydrocarbons. Carbon can form

compounds with hydrogen, oxygen, nitrogen, sulphur etc. Today, million of carbon compounds are known. These compounds are used in our daily life and they have brought lot of changes in our life. They are

being used as a new source of energy, compressed natural gas is being used as automobile fuel. Ethyl alcohol is being mixed with petrol which is being used to motor fuel. They are used in preparation of medicines, colors, textiles, plastic, food preservations, fertilizers, paints, pesticides and insecticides.

Polythene is polymer of ethane which is being used extensively. These days polypropene is also being used as plastic. Soaps and detergents which are commonly used as cleaning agents are also compounds of carbon.

In this chapter, we shall discuss compounds of carbon, hydrogen and oxygen, simple polymers, soaps and detergents.IMPORTANT TERMS AND CONCEPTS1. Organic Compound. It is a compound which contains carbon essentially, hydrogen mostly along with

other elements like oxygen, nitrogen, sulphur, phosphorus and halogens. The term was originally applied to compounds produced by living organisms but now applies to any carbon compounds with the exception of simple compounds such as oxides, carbides, carbon disulphide, cyanides, cyanates and carbonates which are considered to be inorganic, e.g., urea, sugar, cellulose, starch, methane, kerosene, petrol, cooking gas, DDT, BHC, etc are organic compounds.

2. Organic Chemistry. It is a branch of chemistry in which we study organic compounds of carbon.3. Catenation. The property of an element due to which its one atom combines covalently with other

atoms of same element to form long chains and closed rings is called catenation. Carbon shows property of catenation to maximum extent and it is responsible for extraordinary variety of carbon compounds. It is due to small size of carbon, it can form strong covalent bonds.

4. Tetravalent. The atom having valency four is called tetravalent. Carbon is tetravalent atom.5. Hydrocarbons. Compounds of carbon and hydrogen are called hydrocarbons. Methane is the simplest

hydrocarbon. Ethane, propane, butane, ethane, propane, are other example of hydrocarbons. Petroleum is a natural source of aliphatic hydrocarbons (open chain).

6. Molecular formula. It is the formula in which total numbers of atoms of different elements are present. e. g., C2H6 is molecular formula of ethane.

7. Structural Formula. A chemical showing the nature of bonds between different atoms in a molecule is called structural formula e.g.,

H H

H C C H

H HIs structural formula of ethane? It is also called graphical formula.

8. Condensed Structural Formula. The structural formula can be written in condensed form for convenient point of view, e. g., CH3 – CH3 is condensed structural formula of ethane.

9. Electronic. The formula in which covalent bond is indicated by two dots representing two electrons is called electronic formula, e. g. electronic formula of methane is

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CARBON COMPOUNDS .

. .H : C : H

. .H

10. Marsh Gas. Methane is marsh gas as it is formed by decomposition of plant and animal matter in marsh areas.

11. Saturated Hydrocarbons. The hydrocarbons in which valency of carbon is satisfied by only single bond e.g. CH4 (methane), C2H6 (ethane), C3H8 (propane) are examples of saturated hydrocarbons. CH4

(methane has tetrahedral shape.12. Unsaturated Hydrocarbons. The hydrocarbons in which valency of carbon is satisfied by double or

triple bond are called unsaturated hydrocarbons e. g., ethylene (H2C = CH2), acetylene (HC = CH) are examples of unsaturated hydrocarbons.

13. Alkane. They are saturated hydrocarbons with general formula CnH2n + 2 where ‘n’ is equal to 1, 2, 3, 4, 5, etc. e. g., CH4 (methane), C2H6 (ethane), C3H8 (propane).

14. Paraffins. It means little affinity or reactivity. Alkanes are also called paraffins because they have little affinity or reactivity.

15. General Formula or Generic Formula. The formula from which each and every member of a specific family of organic compounds can be derived e. g., CnH2n + 2 is general formula of alkanes where ‘n’ is number of carbon atoms equal to 1, 2, 3, 4, etc.

16. Fuel. It is a substance which produces energy on combustion e. g., alkanes are excellent fuels.17. Combustion. It is a process of burning fuel in presence of oxygen and producing energy. Hydrocarbons

produce carbon dioxide (CO2) and water (H2O) on combustion.18. Isomerism. Compounds having some molecular formula but different structural formulae are called

isomers. Properties of isomers are different e. g., n-butane and iso-butane are isomers of butane (C 4H10) which have different boiling points.

19. Chain Isomerism. The isomerism in which isomers differ only in chain of carbon atoms, e. g., n-butane has straight chain of carbon atoms whereas iso-butane has branched chain. They are chain isomers and this phenomenon is called chain isomerism.

20. Homologous Series. The series of similar compounds having some functional group, similar chemical properties, two successive members differing by CH2, possess general functional and general method of preparation, is called homologous series e. g., CH4 (methane), C2H6 (ethane), C3H8 (propane) are first three members o a homologous series of alkanes.

21. Homologue. Each member of a homologous series is called homologue, or the members of same homologous series are called homologous.

22. Homology. The property due to which compounds exist in various homologous series is called homology.

23. Petrochemicals. A chemical which is obtained from petroleum or natural gas or is obtained from petroleum products is known as petrochemical, e. g., gas, petrol, kerosene, gas oil and diesel oil, lubricating oil, Vaseline, paraffin, wax etc.

24. Alkenes. They are unsaturated hydrocarbons which have general formula CnH2n. They contain double bond which is considered as functional group, e. g., C2H4 (H2C = CH2) and C3H6 (H2C = CH – CH3).

25. Olefins. Olefins mean oil forming. Alkenes are also called olefins because they are oil forming. Most of the oil is unsaturated. Alkenes having general formula CnH2n.

26. Additional Reaction. When two or more atoms are added across the double or triple bond to give one addition product, the reaction is called addition reaction, e. g.,

CH2 CH2Br || + Br2 (aq) |CH2 Bromine Water CH2BrEthane 1, 2-Dibromo ethane

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CARBON COMPOUNDS .27. Hydrogenation. When hydrogen is added across the double or triple bond, this addition reaction is

called hydrogenation, e. g., vegetable oils from ghee on hydrogenation using nickel as catalyst.Ni (Catalyst)

Vegetable oil + H2 Vegetable ghee28. Polymerisation. It is process in which large number of simple molecules under specific condition of

temperature, pressure and catalyst, e. g.,High temp.

nH2C = CH2 ( CH2 CH2 ) n

Ethane High pressure Polythene29. Alkynes. Alkynes are unsaturated hydrocarbons having general formula CnH2n – 2. They contain triple

bond between two carbon atoms. The name of the alkyne as derived from the parent alkanes by replacing the suffix-ane by –yne. e. g., ethyne (HC CH), propyne (HC C – CH3) Acetylene (ethyne has linear shape.

30. Primary Carbon. The carbon atom which is linked with one more carbon atom directly is called primary carbon atom. It is denoted by 1° e. g.,

1° 1°CH3 –CH2 –CH3

31. Secondary carbon. The carbon atom which is bonded with two more carbon atoms directly is called secondary carbon. It is denoted by 2° e. g.,

2°CH3 –CH2 –CH3

32. Tertiary carbon. The carbon atom which is bonded to three carbon directly is called tertiary a carbon atom. It is denoted by 3° e. g.,

3°CH3 –CH –CH3

|CH3

33. Quarternary Carbon. The carbon atom which is bounded to four carbon which atoms directly is called quarternary carbon. It is defined by 4°, e. g.,

CH3

| 4°

CH3 –C –CH3

|CH3

34. Functional Group. It is atom or group of atoms or reactive part of compound which is responsible for physical, and chemical properties of organic compounds e. g., –OH (alcoholic group), –COOH (carboxylic acid). –COOR (ester) where R is alkyl group, –CHO (Aldehyde), –CO (Ketone).

35. Positional Isomers. Those compounds which have same molecular formula but differ in position of functional groups are called positional isomers e. g., By-1-ene and But-2-ene, But-1-yne and But-2-yne, Propan-1-ol and Propan-2-ol are example of positional isomers.

36. Functional Isomers. Those compounds which have same molecular formula but have different functional groups are called functional isomers e. g., CH3CH2CHO (propanal) and CH3COCH (propane are functional isomers.

37. Alcohols. A simple class of compounds which contain carbon, hydrogen and oxygen are alcohols. An alcohol is produced on replacement of one hydrogen atom of an alkane by a hydroxyl ( –OH) group. Thus, by substituting one hydrogen of methane by –OH group, we get a new compound CH3OH called methanol. Alcohols also form homologous series with the general formula CnH2n + 1OH. They are named after the parent alkane by replacing the last letter ‘e’ by ‘ol’.

38. Monohalogen Derivatives of Alkanes. A simple class of compounds which is obtained by replacing one atom of alkane by halogen atom. They form homologous series with the general formula CnH2n + 1 –

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CARBON COMPOUNDS .

X where ‘X’ is an halogen atom (–F, –CI, –Br, –I). If we replace one atom of methane with chlorine atom, we get CH3CI which is called chloromethane (CH3CI).

39. Dihalogen Derivatives. They have general formula CnH2nX2 where ‘X’ is halogen atom e. g., CH2CI2 is called dichloromethane.

40. Trihalogen Derivatives. They have general formula CnH2 – 1X3, e. g., CHCI3 (chloroform), CHBr3

(bromoform), CHI3 (lodoform).41. Tetrahalogen Derivatives. They have general formula CnH2n – 2X4, e. g., CCI4 (carbon tetra-chloride).42. Denatured Spirit. Ethyl alcohol (ethanol) is mixed with poisonous substances like methyl alcohol

(methanol), CuSO4, acetone and pyridine (C5H5N) so as to make it unfit for drinking and it is used as industrial solvent and in spirit lamps.

43. Fermentation. It is a chemical change brought about by biological catalysts called enzymes by enzyme action e. g., milk changing to curd, changing grape juice or mollases (peels of sugarcane) into mixtures containing alcohol on addition of yeast. It is an exothermic reaction. It takes place at moderate temperature.

44. Ferment. The biological catalyst or enzyme which promotes fermentation is called ferment e. g., acetobactor is a ferment used to convert ethyl alcohol to vinegar.

45. Enzyme. They are biological catalysts. They help in breaking complex molecules into simple molecules e.g., invertase is used to convert sucrose into glucose and fructose. Zymase converts glucose to ethanol.

46. Vinegar. It is a dilute solution of acetic acid or ethanoic acid. (7 to 8 %) it is used in pickles.47. Distillation. It is a dilute process of evaporation followed by condensation. It is used to separate

miscible liquids. It is also used to purify volatile liquids.48. Liquors. The drinks like beer, wine, whisky which contain ethyl alcohol are called liquors.49. Antifreeze. It is the mixture which freeze even at very low temperature e. g., mixture of alcohol and

water has a much lower freezing point than that of water. This mixture, known as antifreeze, is therefore used in of vehicles in cold countries, 1, 2-Ethanediol and glycerol are also used as antifreeze.

50. Organic. Organic acids contain the – COOH group know as the carboxylic acid group. The acids are named after the respective alkane containing the same number of carbon atoms, by substituting the last letter of the corresponding alkane by-oic acid, e. g., HCOOH is methanoic acid. They have general formula CnH2n + 1 – COOH. CH3COOH is ethanoic acid.

51. Fatty Acids. The carboxylic acids which contain large number of carbon (more than 10) occur as solids, are known as fatty acids. They are used as mild acids in foods, cold drinks, drugs, perfumes and soaps, e. g., stearic acid (C17H35 COOH), palmitic acid (C15H31COOH).

52. Esters. Compounds which contain the functional group –COO– are called esters. They have general formula.

CnH2n+1COOCnH2n + 1

or simply RCOOR` where R and R` are alkyl groups. ‘R’ can be hydrogen also. They are formed when organic react with alcohol in the presence of concentrated sulphuric acid e. g., CH3COO2H5

(ethyl ethanoate), CH3COOCH3 (methyl ethanoate). Esters have fruity smell. They are used in cold drinks, ice creams, sweets and perfumes. They are also found in fruits.

O O || ||

53. Aldehydes. Aldehydes have general formula CnH2n + 1 – C – H, – C – group is called Carbonyl group Aldehydes have one alkyl group attached to carbonyl group and one hydrogen atom is attached to

O ||

carbonyl group except in case of first member whose formula is H – C – H. O O || ||

The general IUPAC name of the aldehyde is alkanal, e. g,. H – C – H is called methanal, CH3 – C – H

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CARBON COMPOUNDS .

O||

is called ethanal, CH3 CH2 – C – H is called propanal. O ||

54. Ketones. Ketones have general formula CnH2n + 1 – C – Cn H2n + 1

Ketones have two alkyl groups attached to C = O group. The general IUPAC name of ketones is O O || ||

Alkanone, e. g., CH3 – C – CH3 is called Propanone, CH3 – C – CH2 – CH3 is called Butanone.55. Amines. Amines have general formula CnH2n+1 – NH2. The general IUPAC name of amines is

Alkanamine, e. g., CH3NH2 is called Methanamine. C2H5NH2 is called ethanemine.56. Nitro Alkanes. Nitro alkanes have general formula CnH2n+1 – NO2. Their general IUPAC name is nitro

alkanes, e. g.,CH3NO2 is called nitro methane.C2H5NO2 is called nitro ethane.

57. Alkyl Group. The group which have general formula CnH2n+1 are called alkyl groups, e. g., CH3 – is called methyl group, C2H5 – is called ethyl group.

58. Man-made Materials. The materials prepared by man to satisfy his needs are called man-made materials, e. g., synthetic fibres, plastic rubber, soaps and detergents are man made materials.

59. Fibres. They are thread like materials used for making clothes and for other puposes.60. Synthetic fibres. They are polymers made up of one or more units repeating themselves to form very

large molecules. ‘Poly’ means ‘many’ and ‘mer’ means a ‘repeating unit’. Nylon, polyester, carbon fibres are examples of synthetic fibres.

61. Natural Fibres. They are fibres obtained from natural resources, e. g., cellulose is a natural polymer. The wall of all plant cells are made of cellulose. Cotton and jute are natural fibres made of cellulose. Silk and wool are natural polyamide fibres.

62. Nylon. It is a synthetic fibre. It is a condensed polymer of dicarboxylic acids, e. g., (acidic acid with diamines, (e. g., hexamethylene diamine) to form polyamides containing repeating amide (–CONH) group. It is used for making fishing nets, ropes, parachute fabrics and tyre cord. It is also mixed with wool to make long lasting fabrics. The chemical reaction for preparation of nylon is:

O O O O|| || || ||

nHO – C – (CH2)4 – C – OH + n H2N – (CH2)6 – NH2 – C – (CH2)4 – C – NH – (CH2)6 – NH – n

Adipic acid Hexamethylene diamine Nylon 1, 6-hexanedioic acid

63. Polyester. It is another synthetic fibre. It is formed condensation of polyhydric alcohol (e. g., ethylene glycol, and glycerol) and dicarboxylic acid (e. g., terephthalic acid). The reaction between hydroxyl and carboxylic acid groups results in formation of an ester group (–COO–). Since this fibre contains many ester groups, it is called polyester. They are used in the manufacturing of textiles: sarees, dress materials and curtains. Polyester is used for making sails for sail boats, and a variety of other:materials such as water hoses for fibre fighting. The chemical reaction for preparation of terylene (polyester) is:

O O O O|| || || ||

nHO – C – O – C – OH + n HOCH2 – CH2OH – C – O – C – O – CH2 – CH2 – O – n

Terephthalic acid Ethylene glycol Terylene or polyester(1, 2-Benezene dicarboxylic (1,2-ethane diol)

acid)64. Carbon fibres. They are made of long chains of carbon atoms, possess high tensile strength and are

resistant to corrosion. They are made from regenerated or synthetic fibres by heating them in the

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CARBON COMPOUNDS .

absence of oxygen. The fibres decompose to produce carbon fibres. Carbon fibres are used in spacecrafts and for making sports etc.

65. Plastic. Plastic are materials which can moulded or set into a desired shape. Polyamides, polyesters and polythene (polyethylene) are common plastics.

66. Thermoplatics. They soften on heating. This property allows them to be set in a desired shape which is retained on cooling. Polyvinyl chloride (PVC) and polystyrene are examples of thermoplastics.

67. Thermosetting polymers. They are polymers which once set in a given shape by heating cannot be softened or melted on being reheated. These irreversible polymers are called thermosetting polymers, e. g., bakelite and melamine are examples of thermosetting polymers. They contain cross linked chains which prevent the displacement of individual chains on being heated, e. g., Bakelite.

68. Polyvinyl Chloride (PVC). It is a polymer of vinyl chloride (CH2 = CHCI). It is used for making pipes, hoses, electrical insulation, clothing etc.

69. Polyestyrene. A clear colorless thermoplastic material made by polymerisation of styrene C6H5 – CH = CH2. It is used in electrical insulation, packing and in thermal insulation.

70. Bakelite. It is linked condensation polymer of phenol and formaldehyde. It is used for electrical switches and switchboards.

71. Melamine. It is cross linked condensation polymer of phenol and formaldehyde. It is used for making unbreakable crockery. They are very popular in these days.

72. Rubber. It is naturally occurring polymer of isoprene (2 methyl-1, 3-butadiene) It is obtained as a latex from rubber tree. It is coagulated with the help of the acetic acid to get natural rubber. Rubber is elastic in nature. It is thermoplastic.

73. Filter. It is a substance which is added to plastics, paints, rubber, etc. so as to give them strength (hardening) and to reduce the cost e. g., carbon black is added to rubber which acts as filter.

74. Vulcanisation. It is a process of heating natural rubber with sulphur to get vulcanized rubber which retains its shape. Vulcanised rubber is used for making gloves, rubber bands and tubes and football bladders because it is more elastic and works well at low as well as high temperature.

75. Anti-oxidant. It is the material which protests a substance from oxidation on exposure to air, e. g., diphenyl amine [(C6H5)2NH] added to natural rubber acts as an anti oxidant.

76. Tensile strength. The pulling stress which has to be applied to a material to break is called tensile strength e. g., Nylon has high tensile strength.

77. Elasticity. It is the property of a material of regaining its original form and dimension when a force action upon it is removed. Rubber shows the property of elasticity.

78. Hose. It is flexible rubber tube or pipe for conveying water and other liquids like oil.79. Condensation polymerisation. When large number of simple molecules polymerise with the loss of

molecules like water, ammonia, etc it is called condensation polymerisation. The polymers thus obtained are called condensation polymers, e. g., nylon, polyesters etc.

80. Addition polymerization. When large number of simple molecules undergoes addition forming long chain with repeating monomer units, it is called ‘addition polymerisation’ and the polymer formed is called addition polymer. Polythene, polystyrene, polyvinyl chlorides are examples of addition polymers.

81. Cellulose. It is the carbohydrate, compound of carbon, hydrogen and oxygen present in plants, paper, wood pulp etc. It is natural polymer. It is a polymer of starch.

82. Polyester. It is a synthetic fibre consisting of straight chain polyester. It is formed by condensation or 1, 2-ethane-diol and terephthalic acid. It is used in textile industry. It is also called terylene.

83. Synthetic Rubber. Natural rubber is polymer of isoprene. Scientists developed various types of rubber in the laboratory using monomers similar to isoprene. Synthetic rubber has additional desirable.

CH3

|Properties, e.g. neoprene and Thiokol. Isoprene is 2-methyl-1, 3-butadiene (CH2 = C – CH = CH2)

84. Neoprene. It is a polymer of chloroprene (2-chloro-1, 3-butadiene). It does not burn readily due to presence of large number of chlorine atoms. It is not attacked by oils and solvents. It is stable at higher

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CARBON COMPOUNDS .

temperature. Neoprene is used as an insulating material in electrical cables, conveyor belts in coal mines as well for making hoses for transporting oils.The chemical equation for neoprene from chloroprene is:

Polymerisationn CH2 = C – CH = CH2 – CH2 – C = CH – CH2 –

| | Cl Cl n

Chloroprene Neoprene2-chloro-1, 3-butadiene

85. Thiokol. It is another synthetic rubber. It is polymer of 1, 2-dichloro ethane. Sodium polysulphide acts as a polymerizing agent. It is resistant to oils and solvents. It is used for making hoses and linings of vessels used in manufacturing of chemicals, as well as solvent storage tanks. Thiokol mixed with oxidizing agent like oxygen is used as rocket fuel because it is combustible.The chemical reaction for preparation of Thiokol is:

S S S S || || || ||

nCICH2 – CH2Cl + n Na – S – S – Na + n ClCH2 – CH2Cl – CH2 – CH2 – S – S – CH2 – CH2 – 1, 2-dichloroethane Sodium polysulphide Thiokol n86. Saponification. It is sodium or potassium salts of higher fatty acids like stearic acid, palmitic acid, oleic

acid etc, e. g. C15H31COONa (Sodium palmitate) and C17H35COONa (Sodium stearate) etc. C17H35COO CH CH2OH

| |C17H35COO – CH +3NaOH CHOH + 3C17H35COONa

| |C17H35COO – CH2 CH2OH (Soap)glyceryl stearte (fat) Glycerol

88. Glycerol. It is trihydric alcohol CH2OH – CH – CH2OH . It is also called glycerine. It is used | OH

in drugs, cosmetic explosives and transport soaps. Its IUPAC name is propane –1, 2, 3 – triol.89. Hydrophillic. The groups which are attracted by water molecules are called hydrophilic e. g. in soaps –

COONa group and in detergents –SO2Na, SO4Na are hydrophilic.90. Hydrophobic. The groups which are water-repelling are called hydrophobic e. g. in soaps and

detergents hydrocarbon part is water replling i, e., hydrophobic.91. Synthetic detergents. Detergents are made from hydrocarbons obtained from coal or petroleum. They

are sodium or potassium salts of sulphuric acids of benzene or sulphates of unsaturated hydrocarbons of alkene type.

92. Washing powder. They contain about 15-30% detergents by weight. The rest is sodium sulphate and sodium silicate are added to keep the washing powder dry. Sodium tripolyphosphate or sodium carbonate is added to maintain alkalinity which is helpful in removing dirt. Carboxy methyl cellulose (CMC) is added to keep the dirt suspended in water. Sodium perborate acts as bleaching agent.

93. Rules for IUPAC naming of organic compound.(i) Select the longest chain possible. For example, in the following compound, the longest possible chain contains five carbon atoms and not four:

CH3–CH2–CH–CH2–CH3

| CH3

For other compounds than hydrocarbons select a portion of molecule that can serve as the parent compound e. g. in the following compound:

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CARBON COMPOUNDS .

4 3 2 1CH3 – CH – CH2CH2OH

| CH3

rectangle portion serves as a parent compound i.e., buran-1-ol.(ii) For aliphatic hydrocarbons, the number of carbon atoms in present compound is denoted by the proper prefix meth, eth, prop, but, pent, hex for 1, 2, 3, 4, 5, 6, carbon atoms respectively and then the suffix ‘ane’ is added to specify saturated hydrocarbons, alkane. For example, in compound given in (i) parent hydrocarbon contains 5 carbon atoms, so it is called pentane.(iii) Groups attached to the parent chain are indicated by their names and the counting numbers of the carbon atoms on the parent chain to which they are attached are wrriten as prefix.(iv) The counting of carbon chain is done is such a way that sunstituent or functional groups get the lowest number. For example, in the compound given below, numbering of carbon atom is done from left to right to left so as to give minimum number of substituents, i. e., and methyl group.

1 2 3 4CH3–CH–CH2–CH3 is correct way of numbering.

| CH3

4 3 2 1CH3–CH–CH2–CH3 is wrong way of numbering. | CH3

4 3 2 1In compound CH3–CH–CH2CH2OH, numbering will start from left to right so as to give

| CH3

Preference to functional group over the substituent.(v) If several identical groups are present at same or different carbon atoms, prefix di, tri, tetra are used to indicate 2, 3, 4, groups respectively indicating the numbers given to carbon atoms, to which they are attached.

CH3 CH3

|1 2 3 4 1 2 3 4CH3–C–CH2CH3 CH3–CH–CH–CH3

| |

CH3 CH3

2, 2-dimethyl butane 2, 3-dimethyl butaneIn first compound, there are two methyl groups attached at second numbered, carbon atom, so its name is 2, 2-dimethyl butane. Butane is written because parent hydrocarbon contains four carbon atoms. Similarity, in second compound, two methyl groups are present at second and third carbon atoms, so it is named as 2, 3-dimethyl butane.(vi) For double bond, suffix –ene, triple bond, -yne, -ol for alcohols, -al for aldehydes, -oic acid for carboxylic acids, -oate for esters are used. In alkene and alkyne counting number of carbon atom is also mentioned after which double bond or triple is present.

94. Alcohols. Alcohols are carbon compounds containing –OH group attached to Carbon atom. The general formula of alcohol is R–OH where ‘R’ is an alkyl group and –OH is a functional group.An alcohol may also be considered as derived by replacing a hydrogen atom of an alkane by a hydroxyl group.

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CARBON COMPOUNDS .

The name of alcohol is derived by replacing – e is the name of alkane from which it is derived by the suffix – ol. For example methanol (CH3OH), an alcohol is derived by substituting ‘H’ of methane by – OH.The names and formulae of first members of alcohol series and the corresponding alkanes are given in following table 15.1.

Alkane Formula of Alcohol Common Name IUPAC NameCH4

MethaneCH3OH Methyl alcohol Methanol

C2H6

EthaneC2H5OH Ethyl alcohol Ethanol

C3H8

PropaneC3H7OH Propyl alcohol Propanol

C4H10

ButaneC4H9OH Butyl alcohol Butanol

Table 15.1: First four members of alkanes and alcohols95. Ethanol. Ethanol is commonly known as alcohol. It is present in all alcoholic beverages, namely beer,

wine, whisky, cough syrups, digestive syrups and tonics.In industries, alcohol is produced by the fermentation of sugar. Let us understand the process of “fermentation” and other methods of preparation of ethanol.

96. Fermentation. It is slow process in which complex organic compounds such as carbohydrates get converted into simple compounds like alcohol with the help of enzymes. Enzymes are substances which catalyse specific bio chemical reactions. They are highly specific in nature. They are more affective at moderate temperature, i. e., neither high nor low temperature.

97. Lactase. It is enzyme which converts sugar present in milk, i. e., Lactose into Lactic acid. Milk changes into curd by fermentation. Souring of milk and kneaded flour on keeping in hot weather are also due to fermentation.Fermentation was used for the preparation of alcoholic beverages from grape juice and other fruits in presesne of yeast, which contains enzymes.This process is called fermentation because the liquid appears s boiling (fervor to boil) due to the liberation of carbon dioxide gas.Ethanol can be prepared by fermentation of sugar from molasses or sugar or fruits or starch from various grains is first converted into glucose and fructose which have same molecular formula C6H12O6 is presence of an enzyme, invertase. Glucose is polyhydroxy aldehyde, i. e., it contains five hydroxyl groups and one eldehyde group. Its structural formula glucose and fructose are given below:

O||C-H CH2OH| |CHOH C = O| |CHOH CHOH| |CHOH CHOH| |CHOH CHOH| |CH2OH CH2OHGlucose Fructose

98. Fructose. It is polyhydroxy ketone, it has five hydroxyl groups and one ketone group.Methods of Preparation of Ethanol.

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CARBON COMPOUNDS .

(a) From cane Sugar:Cane sugar (Sucrose) has molecular formula C12H22O11, which on hydrolysis in presence of invertase forms glucose and fructose.

InvertaseC12H22O11 + H2O C6H12O6 + C6H12O6

Cane sugar glucose fructose(Sucrose)Glucose and fructose are both converted into ethanol and carbon dioxide in presence of another enzyme called Zymase in absence of oxygen.

ZymaseC6H12O6 2C2H5OH+2CO2

Glucose Zymase

C6H12O6 2C2H5OH + 2CO2

fructose Ethanol(b) From starch. Ethanol can also be obtained by fermentation of starch (C6H10O5)n which is a polymer of glucose.Starch, on hydrolysis gives Maltose (C12H22O11) in presence of diastase as enzyme at 60°C.

Diastage2(C6H10O5)n + nH2O nC12H22O11

Starch MaltoseMaltose gets hydrolysed in presence of Maltase as enzyme to give 2 molecules of glucose at 30°C.

MaltasaC12G22O11 + H2O 2C6H12O6

Maltose glucoseGlucose, on fermentation with Zymase gives ethyl alcohol and carbon dioxide.

ZymaseC6H12O6 2C5H5OH + 2CO2

Glucose ethanol carbon dioxideFermentation is an exothermic process. It is carried out at 20 – 30° in absence of air otherwise acetic acid will be formed.(c) Hydration of alkane now days a major amount of ethanol used for commercial purpose is produced by reacting ethane with H2O in presence of sulphide acid.

H2SO4

CH2 = CH2 + H2O CH3 – CH2OHEthene water Ethanol

(d) Hydrolysis of Alkylhalides (Haloalkanes)Alkylhalides, on reaction with aqueous solution of caustic potash (KOH) is also called potassium hydroxide or caustic soda (NaOH), also called sodium hydroxide undergoes hudrolysis and forms alcohol, e. g., Ethyl chloride or Ethyl bromide on hydrolysis with KOH (aq) or NaOH (aq) gives ethyl alcohol.

C2H5Cl + KOH (aq) C2H5OH + KClchloro Potassium Ethanolethane hydroxide

C2H5Br + NaOH (aq) C2H5OH + NaBrBromo Sodium Ethanolethane hydroxide

99. Physical Properties of Ethanol.Pure ethanol is a colorless liquid.It has a specific smell and burning taste.

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CARBON COMPOUNDS .

Its boiling point is 351 K which is higher than corresponding alkanes.It is soluble in water, i. e., it is miscible with water in all properties.Chemicals properties of Ethanol(i) Dehydration. Ethanol, when heated with conc. H2SO4 at 443 K or Al2O3 at 623 K undergoes dehydration loses water molecule to from alkene.

Conc. H2SO4, 443 KCH3CH2OH CH2 + CH2 + H2OEthane or Al2O3, 623 K Ethene(ii) Reaction with sodium. Alcohols are very weakly acidic. Ethanol reacts with sodium metal to form sodium ethoxide and hydrogen gas.

2C2H5OH + 2Na 2C2H5ONa + H2

Ethanol Sodium Sodium Hydrogenethoxide

Experiment 1. To show the reaction between ethanol and sodium metal.Procedure. Take 2ml of pure ethanol in a test tube.Add a small clean dry piece of sodium metal into it very carfully.Collect the gas in an inverted test tube placed over the mouth of reaction tube.Remove the reaction tube away.Bring a burning splinter near the mouth of the gas tube.Observation. The gas burns in air with a pop sound which takes place in case of H2 gas.Conclusion. Ethanol reacts with sodium metal and liberates H2 gas.(iii) Oxidation. (a) With chromic anhydride (CrO3)

CrO3 inCH3CH2OH CH3CHOEthanol CH3COOH EthanalExperiment No. 2. To study oxidation of ethanol with CrO3 (Chromic anhydride).Procedure. Take about 3 ml of ethanal in a test tube. Observe the smell of ethanol.

Add 5% solution of chromic anhydride in glacial acetic acid (pure acetic acid) drop by drop to it.Keep on adding this solution until the color of CrO3 does not disappear.Observe the smell of the reaction mixture after the reaction is complete.

Observation. A specific smell is observed due to oxidation of ethanol to ethanal (CH3CHO).Conclusion. Ethanol gets oxidized to ethanal with CrO3 in acetic acid.(iv) Oxidation with alkaline KMnO4

AlkalineCH3CH2OH + [O] CH3COOH + H2OEthanol KMnO4 Ethanoic acid

Experiment No. 3. To study oxidation of ethanol with alkaline KMnO4

Procedure. Take about 3 ml of ethanol in a test tube and observe its smell.Add 5 per cent aqueous solution of KMnO4 in NaOH solution drop by drop.The purple color of potassium permanganate gets decolorized during the reaction.When all the alcohol gets consumed, the reaction stops and the purple color persists.Warm the tube gently in hot water bath during the reaction.Observe the smell of the product formed in the reaction.Observation. The product formed has vinegar like smell.Conclusion. Alkaline potassium permanganate oxidizes ethanol to ethanoic acid.(v) Oxidation with acidified Potassium dichromate. Ethanol is oxidized to ethanoic acid with the help of acidified K2Cr2O7

K2Cr2O2/H2SO4 (Conc.)CH3CH2OH + 2 [O] CH3COOH + H2OEthanol Ethanoic acid

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CARBON COMPOUNDS .

During this reaction, orange color of K2Cr2O7 changes to green. Therefore, this reaction can be used for the identification of alcohols.(vi) Esterification. Ethanol reacts with ethanoic acid in presence of concertrated H2SO4 to form ethyl ethanoate and water. The compound formed by the reaction of an alcohol with carboxylic acid is known as ester and the reaction is called Esterification. Esters are sweet fruity smelling compounds because they occur in fruits. They are used in ice creams, cold drinks and perfumes. The reaction takes place as follows.

Conc.CH3COOH + C2H5OH CH3COOC2H5 + H2OEthanoic acid Ethanol H2SO4 Ethyl Ethanoate WaterConc. H2SO4 acts as dehydrating agent it removes water formed otherwise ester formed will get hydrolysed.Saponification. The reaction which involves hydrolysis of ester with the help of caustic soda (alkali) is known as saponification.When ethyl ethanoate is treated with sodium hydroxide, undergoes saponification ethyl alcohol and sodium ethanoate are formed.

CH3COOC2H5 + NaOH CH3COONa + C2H5OHEthyl Sodium Sodium Ethanolethanoate hydroxide ethanoate

Experiment 4. To study saponification of ester with the help of alkali.Procedure. Take 2 ml of ethyl ethanoate and 4 ml of sodium hydroxide solution in a boiling tube.Two separate layers will be formed because the two liquids do not mix with each other.Heat the mixture in a water bath at about 330 K with occasional shaking the contents of the tube.Continue heating for about 20 minutes.Observe that ester layer which was not mixing (immiscible) with water has appreciably decreased.Observation. The products formed out of reaction mix with water.Conclusion. Ethyl ethanoate reacts, with sodium hydroxide to form sodium ethanoate and ethanol which are soluble is water.(vii) Combustion. Ethanol is highly inflammable liquid it catches fire very easily. It burns with blue flame in presence of oxygen to form carbon dioxide and water.

C2H5OH + 3O22CO2 + 3H2O (l)Ethanol oxygen Carbon Water

Dioxide100. Uses of Ethanol.1. Ethanol is present in alcoholic beverages such as beer, wine, and whisky.2. Ethanol is used as antiseptic for sterilizing wounds.3. Ethanol is used in cough syrups, digestive syrups and tonics.4. Ethanol is being mixed with petrol and is used as motor fuel. This mixture is called power alcohol.5. A mixture of ethanol and water has lower freezing point than water. This mixture is known as antifreeze

and is used in radiators of vehicles in cold countries and at hill stations.6. Ethanol is used for preparation of chloroform, iodoform, ethanoic acid, ethanal, ethyl ethanoate etc.7. Ethyl alcohol is used as hypnotic (induces sleep).8. Ethanol can be used as a fuel.101. Harmful effects of drinking alcohol.1. If ethanol is mixed with CH3OH (methanol) and consumed, it may cause serious poisoning and loss of

eyesight.2. It causes addiction (habit forming) and mixes with blood. It damages liver if taken regularly in large

amount.3. The person loses all senses of discrimination under its influence.4. Higher amount of consumption of ethanol leads to loss of body control and consciousness. It may even

cause death.

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CARBON COMPOUNDS .

Therefore, we should not drink alcohol under any circumstances because it leads to wastage of time, wealth and spoils health.

102. Aldehydes and ketones.Aldehydes and ketones are compounds containing carbonyl ( C = O) group. In aldehydes, carbon of C = O group is attached to an alkyl group and a hydrogen atom.In ketones, carbon of carbonyl group is attached to two alkyl groups. The two alkyl groups may be same of different. For example,

R C = O or RCHO is an AldehydeRR C = O or RCOR` is a KetoneRWhere R and R` are different alkyl groups.Aldehydes are named by replacing- e from the name of alkane by the suffix-al and ketones, are named by replacing – e of alkane by the suffix – one.

HCHO, the simplest aldehyde is derived from methane and is named as methanal.CH3CHO, the aldehyde is derived from ethane and is called ethanal.

Similarly, CH3COCH3, the simplest ketone is derived from propane and is called propanone.Alkane Formation of Aldehyde Name Formula of Ketone Name

O ||

CH4 (Methane) H – C – H Methanal – –O||

C2H6 (Ethane) CH3 – C – H Ethanal – –O||

C3H8 (Propane) CH3CH2 – C – H Propanal CH3COCH3 Propanone O ||

C4H10 (Butane) CH3CH2CH2 – C – H Butanal CH3COCH2CH3 Butanone O ||

C5H12 (Pentane) CH3CH2CH2CH2 – C – H Pentane CH3COCH2CH2CH3 Petane-2-oneTable 15.2. Formulae and names of simple aldehydes and ketones.

103. Methanal (HCHO). The common name of the simplest aldehyde is Formaldehyde. It has specific pungent smell. It is used for preserving biological specimens. Formalin, in which specimens are preserved is 35-40% solution of formaldehyde in water.

104. Methods of preparation of methanal.From Methanol. Methanal is prepared by controlled oxidation of methanol (CH3OH) at 873-923 K using silver or iron oxide Molybdenum oxide as catalyst.

873-923 K2CH3OH + O 2HCHO + 2 H2O

CatalystMethanol HoO3 Methanal

105. Physical properties of Methanal.1. Methanal is a colorless gas. It has pungent smell.2. It has boiling point 252 K.3. It is highly soluble is water.

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CARBON COMPOUNDS .106. Chemical properties of methanal.

(i) Oxidation.(a) With Acidified KMnO4

Methanal is oxidized to methanoic acid with the help of oxidizing agent like acidified KMnO4.O O|| ||

KMnO4/dil. H2SO4

H – C – H + [O] H – C – OH Methanal Methanoic acid.(ii) Oxidation with Ammonical silver nitrate solution or Tollen’s reagent: Methanal reacts with Tollen’s reagent and gets oxidized to methanoic acid and silver mirror is formed. The reaction takes place is as follows:

AgNO3 + 2NH4OH [Ag(NH3)2]NO3 + 2H2OAmmonical silver nitrate

HCHO + 2[Ag(NH3)2]NO3 + 2NH4OH HCOOH + 2Ag + 2NH4NO3 + 4NH3 + H2OMethanal Methanoic acid (Silver mirror)Experiment No. 5. To demonstrate reaction of Tollen’s reagent with methanal.Procedure. Take 1-2 ml of AgNO3 (silver nitrate) solution in a clean test tube.Add 2-3 drops of ammonium hydroxide and shake the contents.Add excess of NH4OH till back precipitate formed gets dissolved.This solution is ammonical silver nitrate or Tollen’s reagent.Add 3-4 drops of formaline (aqueous solution of methanal) and shake the contents.Heat the test tube in hot water at about 330 K for 5-10 minutes.Observation. A shiny silver mirror is formed along the sides of the tubes.Conclusion. Aldehydes such as methanal gets oxidized by Tollen’s reagent to HCOOH and Tollen’s reagent gets reduced to shiny silver. Thus methanal acts as a reducing agent.(iii) Oxidation using Fehling’s solution. Fehling’s solution is alkaline copper hydroxide which oxidizes methanal to methanoic acid and gets reduced to brick red precipitate of Cuprous oxide.Methanoic acid reacts with NaOH to form sodium methanoate. The reaction which takes place is as follows:

HCHO + 2Cu(OH)2 + NaOH HCOONa + Cu2O + 3H2OMethanal Sodium (brick red ppt)

methanoateExperiment 6. To demonstrate the reaction of methanal with Fehling’s solution.Procedure. Take 2 ml of each of Fehling’s solution ‘A’ containing CuSO4 and ‘B’ containing alkaline Rochhle salt (sodium potassium tartarate) solution is separate clean test tube.Mix the two solutions ‘A’ and ‘B’ in equal proportion.Add 2 ml of formaline (methanal dissolved in water).Heat the mixture on water bath for 5-10 minutes.Observation. A brick red precipitate of copper (I) oxide is formed.Conclusion. Aldehydes like methanal gets oxidized by Fehling’s reagent to methanoic acid which reacts with NaOH to form sodium methanaote. Fehling’s reagent contains Cu2+ iron which gets reduced to Cu2O (brick red precipitate).Glucose. It is an aldehyde is produced in our body by degradation of food that we eat.A person suffers from ‘diabetes’ if the concentration of glucose in blood increases beyond a certain limit. The excess of glucose comes out in urine which can be tested with the help of Benedict’s reagent. Benedict’s reagent is prepaid by dissolving copper sulphate in water containing citric acid and sodium carbonate. Glucose gets oxidized to gluconic acid and Benedict’s reagent containing Cu2+ ion gets reduced to Cu2O (brick red precipitate).

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CARBON COMPOUNDS .

CHO CHO| |(CHOH)4 + 2CuSO4 + Na2CO3 (aq) (CHOH)4 + Cu2O + CO2 + Na2SO4

| | (Brick red ppt)CH2OH CH2OHglucose gluconic acid(iv) Reduction of Methanal. Methanal is reduced to methanol by treating it with H2 gas in presence of finally divided palladium as catalyst.

O|| Pd

H – C – H + H2 CH2OHMethanal Methanol

(v) Reaction with HCN. Methanal contains bond between carbon and oxygen atoms C = O.Compounds containing double bond can undergo addition reactions. Therefore, methanal undergoesAddition reaction with HCN (Hydrogen Cyanide).

H H OHC = O + – C

H H CNMethanal cyanohydrin

(vi) Reaction with Grignard reagent. (Alkyl magnesium halide) Methanal reacts with grignard reagent followed by hydrolysis to form alcohol e.g.

H H OMgBr H OH Br

C = O + C C + Mg

H H CH3 H CH3 OH

Methanal Methyl magnesium CH3CH2OH HydroxyBromide magnesium

Bromide(vii) Reaction with Alkalies: Cannizaro’s Reaction. Methanal, on reaction with concentrated solution of KOH or Na OH undergoes auto oxidation and reduction to form methanol and sodium formate.2HCHO + NaOH (conc.) CH3OH + HCOONaMethanal Methanol Sodium methanoateIn the above reaction, gets reduced to methanol and gets oxidized to HCOOH. HCOOH (methanoic acid) reacts with NaOH to form sodium mehtanoate (HCOONa).(viii) Reaction with Ammonia. Methanal reacts with ammonia to form hexamethyl tetramine. It is also known as Urotropine. It is used as urinary antiseptic.

6HCHO + 4NH3 (CH2)6 N4 + 6H2OMethanal Hexa methylene

tetramine(urotropine)

(ix) Condensation with phenol. Formaldehyde undergoes condensation with phenol and forms a cross linked thermosetting plastic called Bakelite.

OH OH OHCH2OH CH2OH

+ HCHO + +

Phenol Methanal Bakelite (Cross linked Polymer)107. Uses of Methanal. Graphics By:- R.Dhawan 15 Written By:- Raj Kumar Badhan

H2O / H+

OH–

CARBON COMPOUNDS .

1. Aqueous solution of formaldehyde called formaline is used for preserving biological specimens.2. Methanal is used for making urotropine which is used as urinary antiseptic.3. Methanal is used to make bakelite which is used for making electrical switches and switch boards because it is heat resistant.4. It is used as reducing agent.5. It is used for silvering of mirror so as to get looking mirror.6. Methanal is used as disinfectant and germicide.

CH3

Propanane. C = O Propanane is simplest ketone. Its common name is dimethyl ketone.CH3

Its most popular name is acetone. It is used as a solvent. It is also used as nail polish remover.108. Methods of preparation of Acetone.

(i) Catalytic oxidation of propan-2-ol. Propan-2-ol (Isopropyl alcohol) gives acetone using heated copper at 573 K. This reaction is also called dehydrogenation, removal of H2. Oxidation also involves removal of hydrogen.

CH3 CH3

CH – OH C = O + H2

CH3 CH3

IUPAC name: Propan-2-ol PropanoneCommon name: (Iso propyl alcohol) (Acetone)

(ii) Dry distillation of calcium acetate. Calcium acetate, on dry distillation, i.e., heating solid and condensing the vapours formed gives acetone (propane).

OCH3COO ||

Ca CH3 – C – CH3 + CaCO3

CH3COOCalcium ethanoate Propanone(Calcium acetate).

(iii) From Cumene. Propanone is commercially prepared by oxidation of cumene followed by acidic hydrolysis. Phenol is another important product formed.

CH3 CH3

| |CH3 – CH – O2 CH3 – C – O – O – H CH3 – C – CH3 + C6H5OH

| |C6H5 C6H5 Propanone PhenolCumene Cumene hydroperoxide

(2-phenyl propane)C6H5 is called phenyl group.

OR

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Cu573 K

Drydistillation

heatH2O / H+

CARBON COMPOUNDS .

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