15ORGANIC COMPOUNDSAfter completing this lesson, youwill be able to:define organic chemistry and organic compounds.This is 5 days lesson(period including homework)explain why there is such a diversity and magnitude of organic compounds.classify organic compounds on structural basis.explain the use of coal as a source of both aliphatic and aromatic hydrocarbons.explain the use of plants as a source of organic compounds.explain that organic compounds are also synthesized in the lab define functional groups and homologous series.ReadingINTRODUCTIONThere are two main classes of chemical compounds, inorganic and organic. They areclassified on the basis of source from which they were derived. The compounds which were ofmineral origin were known as inorganic such as table salt, marble, carbon dioxide etc. and thoseof vegetable or animal origin were called organic for example; acetic acid (from vinegar), alcohol(from wine), tartaric acid (from grapes) etc.Organic chemistry is concerned with the chemistry of living material or substances whichwere at one time alive. It is therefore concerned with living plants or animals or substances likecoal and oil which are derived from living plants (coal), or from microscopic sea organisms (oil).Organic chemistry is now defined as the chemistry of compounds of carbon as carbon isthe essential element in all organic compounds. However there are several compounds likecarbon monoxide (CO), carbon dioxide (CO2), carbon disulphide (CS2), carbonates (CO3 -2 ),bicarbonates (HCO3 -1 ), Cyanides (CN -1 ), thiocynates (SCN -1 ) etc are studied in inorganicchemistry because of their properties.Modern definition of organic chemistry:Organic chemistry is that branch of chemistry which deals with the study of compounds ofcarbon and hydrogen (Hydrocarbons) and their derivatives.
15 Organic Compounds15.1 SOURCES OF ORGANIC COMPOUNDS15.1.1 Fossil RemainsThe main sources of organic compounds are coal, petroleum and natural gas. These arecalled fossil fuels.I – CoalCoal is one of major source of organic compounds. It yieldscoke and coal-tar on pyrolysis or destructive distillation. More than200 organic compounds have been directly isolated from coal-tar.These coal-tar products form the starting materials for themanufacture of thousands of useful aromatic compounds, includingperfumes, drugs, dyes, photographic developers, and others.Points to RememberImportant products preparedfrom petroleumMethane (CH4)Ethylene (CH2=CH2)Acetylne (CHCH)Propene (CH3CH=CH2)Benzene C6H6Toluene C6H5CH3Xylene C6H4(CH3)2II - PetroleumIn some parts of the world, a black thick sticky liquid seeps out of the ground. This liquid iscalled petroleum or crude oil. Petroleum is a complex mixture of hydrocarbons whosecomposition varies according to its place of occurrence.III - Natural Gas:It is a mixture of low boiling hydrocarbons. Major portion of the natural gas is methane (CH4about 85%); other gases include ethane, propane and butane. It is formed by the decompositionof organic matter.In Pakistan there are vast reserves of gas at Sui in Baluchistan, Sind and Punjab.15.1.2 Plants and Natural Product <strong>Chemistry</strong>Many organic compounds are obtained directly from plant and animal sources by suitablemethods of isolation. A few familiar examples are carbohydrates (cellulose, sugars, starches),proteins (silk, wool, casein, food proteins, fats and oils (cottonseed, soybeans oils, lard, butter),alkaloids (quinine, morphine, strychnine), hormones, vitamins, perfumes, flavors, resins.15.1.3 Partial and Total SynthesisSimple organic compounds derived from petroleum or coal has been converted intothousands of useful materials by synthetic methods. Many examples might be cited of syntheticorganic compounds replacing those obtained from natural sources, such as dyes, rubber, fibersplastics, drugs, vitamins. In many cases the synthetic materials are superior to the naturalcompounds. For example, synthetic dyes are superior to those of natural origin. In other casesthe synthetic material are entirely unknown in nature and fill the requirements not satisfied fromany other source. Examples are ether, glycol, mercurochrome, aspirin, and the sulpha drugs.Synthetic organic chemistry touches almost every phase of life.15.1.4 FermentationFermentation is defined as the production of chemicals by the action of micro-organism.By employing appropriate organism hosts of useful substances are produced including alcohols,acids, vitamins and antibiotics.103
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