Kinetic examinations were made on the stability of valethamate bromide (2-diethyl-aminoethyl 3-methyl-2-phenylvalerate methobromide)(I) and its tertiary amine, 2-diethylaminoethyl 3-methyl-2-phenylvalerate hydrochloride (II), in aqueous solution and the following conclusions were drawn. I and II undergo hydrolysis in aqueous solution to form an amine (amines-) corresponding to 3-methyl-2-phenylvaleric acid and its reaction rate follows a pseudo-first order reaction. This hydrolysis is catalyzed by hydrogen or hydroxyl ton and shows a pH-rate profile as given in Fig.4. Within the experimental range, however, there was no effect of ionic strength or of buffer solution. Stability of the quaternary ammonium salt (I) and tertiary amine (II) did not differ greatly by comparing their kH but kOH of II was approximately 100 times greater than that of I. Activation energy and frequency factor of II were smaller than those of I. These facts suggest that in protonated amine type, II has an intramolecular catalytic action proposed by Hansen and others.10
