Kinetics and mechanism of the additive reaction of aniline with dicyandiamide

Kinetics of the additive reaction of aniline with dicyandiamide resulting in phenylbiguanide production was studied based on the analysis of reaction rate by high performance liquid chromatography. It is a second-order reaction on the condition of the constant temperature and acidity. It is first-order for both aniline and dicyandiamide. The reaction rate is influenced evidently by acidity. It reaches its maximum at pH 2.6. The mechanism for this reaction was suggested that aniline is nucleophilic reagents additive with the protonated cyano-group in dicyandiamide. The rate equation derived from the mechanism can describe the experimental results well. The reaction rate calculated from the rate equation reaches its maximum at pH 2.5, which is close to the experimental result. For different aromatic amine adding to dicyandiamide have the same reaction order, the mechanism ought to be the same. Published in Russian in Kinetika i Kataliz, 2009, Vol. 50, No. 3, pp. 379–385. The article is published in the original.