11.2 Sources of Organic Compounds

Organic compounds are prepared naturally by animals and plants. Animals synthesize two main groups of organic compounds: proteins and fats. Proteins are meat, mutton, chicken and eggs, etc. Fats are present in milk, butter, etc. Plants synthesize; carbohydrates, proteins, fats, vitamins, etc

Moreover, dead plants buried under Earth's crust are converted through biochemical processes to coal, petroleum and gas. These materials are the main sources of organic compounds. We can get thousands of organic compounds by the destructive distillation of coal and fractional distillation of petroleum.

Details of each source are given in figure below:

11.2.1 Coal

Coal is a blackish, complex mixture of compounds of carbon, hydrogen and oxygen. It also contains small amounts of nitrogen and sulphur compounds:

Coal was formed by the decomposition of dead plants buried under the Earth's crust millions of years ago. Conversion of wood into coal is called carbonization. It is a very slow biochemical process. It takes place in the absence of air under high pressure and high temperature over a long period of time (about 500 millions of years) as shown in figure 11.2. Wood contains about $40\%$ carbon, so depending upon the extent of carbonization process, four types of coal are found. These types differ with respect to carbon content, volatile matter and moisture. Table 11.2 shows the detail of contents of different types of coal and their uses in daily life and industry.