Nucleotides are nucleoside phosphate esters. There are three potential positions for esterification in ribonucleotides (2', 3', and 5') and two in deoxyribonucleotides (3' and 5). The esters of mononucleotides are predominately 5' in nature. Phosphodiesters of polynucleotides involve the 5 and 3 -carbon atoms. Hydrolysis of RNA catalyzed by pancreatic RNAse or alkali yields 2' and 3' esters and cyclic 2,3 diesters. Hydrolysis by acid yields 2'-, 3 and 5-derivatives. Hydrolysis of DNA. catalyzed by pancreatic DNAse yields the 5'-ester derivatives. Hydrolysis by other DNAses can yield the 3' derivative. The inability of DNA to form 2 3'-phosphate diesters accounts for the stability of DNA in alkali. RNA, which can form the 2',3'-diester intermediates, is unstable in alkali.