Abstract
When organic compounds were first found to function as accelerators for the vulcanization of rubber, Peachey and others attributed their activity, at least in part, to the basicity of the substances employed. Patents, to mention but one, were issued stating that there was a specific order of basic strength beneath which accelerating activity would not occur. We have already shown that this is not necessarily true, since acceleration was observed with a weaker base than the patent would have permitted. However, the whole subject has been dormant for many years. The results reported here indicate that there is a real correlation between accelerating power and basic strength: In a closely related series of compounds e.g., aniline, methylaniline, dimethylaniline, the accelerating power, as measured by combined sulfur, is a linear function of the logarithm of the basic dissociation constant, Kb. This relationship has been observed most strikingly with o-, m-, and p-phenylenediamines, and with o-, m-, and p-toluidines. It has been observed also with aniline, diphenylamine, and triphenylamine, and with mono-, di-, and triphenylguanidines. Guanidine itself does not fall into line, but exhibits a behavior comparable with that of sodium hydroxide, which it approaches in basicity (approximately 103 to 104 times the phenyl-substituted compounds).
The Basic Dissociation Constant of Valine