Question

(a) Why does carbon form compounds mainly by covalent bonding?
(b) List any two reasons for carbon forming a very large number of compounds.
(c) An organic acid 'X' is a liquid which often freezes during winter time in cold countries, has the molecular formula C₂H₄O₂. On warming it with ethanol in the presence of a few drops of concentrated sulphuric acid, a compound 'Y' with a sweet smell is formed.
(i) Identify 'X' and 'Y'.
​(ii) Write a chemical equation for the reaction involved.

Answer 1

(a) The electronic configuration of carbon is 2, 4. The electron present in its outer most shell is 4 but for the stability, the number of electrons has to be 8. So, carbon can neither lose 4 electrons nor gain 4 electrons to complete its octet. For losing or gaining electrons from the outer-most shell, we require an enormous amount of heat/energy, which is not possible in nature. Hence, the four electrons present in the outer-most shell will try to share with other four electrons in order to fulfill their octet. That is why it forms covalent bonds.

(b) Two of the main reasons because of which carbon forms a large number of organic compounds are:
1. Tetravalent nature of carbon.
2. Greater C-C bond strength.

(c) Organic compound "X" freezes in colder countries must be a carboxylic acid containing molecule. So, the molecular formula will be CH₃COOH.
When a carboxylic acid is treated with alcohol in the presence of sulphuric acid, it gives a sweet-smelling compound ester. So, when ethanoic acid treated with ethanol, it will give ethyl ethanoate.
Hence, X will be ethanoic acid and Y will be ethyl ethanoate which is a sweet smelling compound.

(ii) The reaction involved is as follows:
$\underset{\mathrm{Ethanoic}\mathrm{acid}}{{\mathrm{CH}}_3\mathrm{COOH}}+\underset{\mathrm{Ethyl}\mathrm{aclochol}}{{\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{OH}}\stackrel{{\mathrm{H}}_2{\mathrm{SO}}_4}{\to }\underset{\mathrm{Ethyl}\mathrm{ethanoate}}{{\mathrm{CH}}_3{\mathrm{COOCH}}_2{\mathrm{CH}}_3}+{\mathrm{H}}_2\mathrm{O}$