The Enthalpy of Hydrolysis of Various 3',5'- and 2',3'-Cyclic Nucleotides

The enthalpy of hydrolysis of the 3'-bond of several cyclic 3',5'-nucleotides and of the 2'-bond of several cyclic 2',3'-nucleotides has been measured calorimetrically. In each case, the enthalpy was indicative of a high energy bond, although values for different compounds varied from -7.7 to -14.1 kcal mole-1. The enthalpy of hydrolysis of the cyclic 3',5'-nucleotides, but not that of the cyclic 2',3'-nucleotides, was markedly affected by the nature of the base.