This alkali is formed by carbon, hydrogen, oxygen and nitrogen. It contains 15% nitrogen. Alkaline compounds form rings. Based on the number of rings, nitrogenous bases can be divided into two groups.
(i) Purines: Dicyclic nitrogenous bases are called purines. Its common symbol is C5H4N4. It is composed of Adenine and Guanine.
(ii) Pyrimidine: A cyclic nitrogenous base is called pyrimidine. Its common symbol is C4H4N2. It is composed of Thymine, Cytosine and Uracil.