The very word organic means that relates to life. This is of vital importance and hence we shall devote in this chapter to a systematic study of organic chemistry. We know that organic compounds are vital for sustaining life on earth and include molecules like DNA which is called deoxyribonucleic acid and proteins. These constitute essential compounds of our blood, muscle and skin. In addition to this organic chemistry finds application in materials like clothing, fuels ,polymers, dyes and medicines. It is therefore essential to study the basic organic structural features the techniques of isolation purification and systematic study and the nomenclature of organic compounds.
Organic chemistry is a branch of chemistry which deals with the compounds of carbon. About 150 years ago, matter was classified as inorganic and organic depending upon the source. The matter which was obtained from minerals was called inorganic and the matter obtained from living systems, such as animals, plants, etc., was called organic. It was Lavoiser (1743-1794) who showed that all organic compounds contain carbon, hydrogen and frequently oxygen and nitrogen. Organic compounds had several typical properties, such as low melting points and combustibility, which were quite different from compounds obtained from minerals.
tal Force Theory
Berzelius (1779-1846), a Swedish chemist, proposed that organic compounds are only produced by animals and plants. They have a mysterious or some vital force which enables them to synthesize organic compounds. Organic compounds cannot be synthesized in the laboratory as the apparatus do not have the vital force needed to synthesize organic compounds. The vital force theory had no scientific logic but was widely believed till a few organic compounds were synthesized in laboratories from inorganic compounds.
In 1828, a German chemist, Wholer synthesized urea from ammonium cyanate which is an inorganic compounds.
Later, more organic compounds were synthesized. For example, acetic acid was synthesized from carbon and hydrogen by Kolbe in 1845.
Oxalic acid was synthesized from cyanogen (CN)2 which is an inorganic compound.
Now, thousands of organic compounds of plant and animal origin have been synthesized in laboratories, without the help of the vital force. Therefore, as such there is no difference in organic and inorganic compounds. However, this classification is still used and the compounds of carbon are called organic compounds. However, compounds, such as carbonates, bicarbonates, carbon monoxide, carbon dioxide, etc., though containing carbon, are not included as organic compounds.
Organic Chemistry as a Separate Branch of Chemistry
Compounds of carbon are treated as a separate class because there are several properties which make them quite different from the compounds from the compounds of other elements. Therefore, these are studied separately as organic compounds. Some of the properties which make them different from the compounds of other elements are:
- Large number
The number of organic compounds is very large, more than a million. It is much more than the compounds of all other elements put together.
- Fewer constituent elements
Organic compounds are formed from a smaller number of elements, such as carbon, hydrogen, oxygen, nitrogen, sulphur, phosphorus, etc.
It is a property possessed by a carbon atom to link with another carbon atom, forming long chains and rings of different sizes. This is the reason why carbon forms a large number of compounds.
- Covalent nature
Organic compounds are formed by covalent linkages. For this reason organic compounds have low melting and boiling points. Organic compounds have low solubility in polar solvents but are soluble in organic (nonpolar) solvents.
Most organic compounds are inflammable while inorganic compounds are noninflammable.
- Slow reaction
When organic compounds reacts with other compounds or reagents, their reactions are quite slow and form several side-products. That is why yields of organic reactions are generally low.
- High molar mass
Many of the organic compounds have a very high molar mass.
- Less stable
Most organic compounds are less stable and decompose on heating.
The phenomenon of isomerism is quite common in organic compounds. Isomerism is the phenomenon of the existence of different compounds having the same molecular formula.
Series Organic compounds form well-defined groups of compounds having similar properties, the same functional group and the same general formula. The next group in the homologous series contains one CH2 group more than the previous one.
The members of a homologous series can be prepared by their general methods of preparation. These show a regular gradation in their physical properties, such as melting point, boiling point, solubility, density, etc.
By studying one member of homologous series, one can know methods of preparation and properties of all other members of the series. It makes the study of organic chemistry easy and simple.