Kinetics of reactions in heterocycles. Part IV. The reaction of chloropurines and their 9-methyl derivatives with sodium ethoxide or piperidine

Abstract

The kinetics of reaction of 2-, 6-, or 8-chloro-9-methylpurine with sodium ethoxide in ethanol reveal that, at 20°, the 8-chloro-compound (I) is much more reactive than the 6-isomer, and that the 2-chloro-compound is the least reactive. Kinetics of reaction of 2-, 6-, or 8-chloropurine anions with sodium ethoxide in ethanol show that, at 120°, 8-chloropurine anion is the least, and the 6-chloro-compound the most, reactive. The differences are due mainly to differences in energy of activation. The kinetics of reaction of unmethylated chloropurines with piperidine in ethanol are complicated by small amounts of the more reactive neutral molecule in the predominantly anionic species. Ionisation constants and ultraviolet spectra are recorded.