APPARENT MOLAR HEAT-CAPACITIES OF SOME ALKYL DERIVATIVES OF 2-AMINOPURINE, ADENINE AND GUANINE IN DILUTE AQUEOUS-SOLUTION AT 25-DEGREES-C

The apparent molar heat capacities C(p,phi), and densities of adenine, 2-aminopurine, 9-methyladenine, 2,2-dimethylaminopurine, 9-ethylguani ne, 2-methylamino-9-methylpurine, 2-dimethylamino-9-methylpurine, 9-me thyl-2-butyladenine, and 6,9-dimethyl-8-butyladenine were determined e xperimentally using a differential adiabatic scanning microcalorimeter DASM-1M and an Anton Paar DMA 60/602 digital densimeter. In the serie s of alkylated adenines and 2-aminopurines, a linear dependence was fo und between the partial molar heat capacities C(p,2)theta and the numb er of substituted methylene groups n(CH2) belonging to the skeleton of the molecule. The experimental data of the apparent molar heat capaci ties of 9-methyl-2-alkyladenines and 6,9-dimethyl-8-alkyladenines indi cated erratic changes in DELTAC(p,2)THETA with elongation of the n-alk yl chain.