Influence of aniline, pyridine and pH on the title reaction has been studied in 50% aqueous ethanol. , Transformation of III into IV is rate-limiting at low pH values, the reaction rate being inversely proportional to the proton concentration. Catalytic effect of both aniline and lyate ions becomes increasingly significant with increasing pH, and deprotonation of the intermediate II becomes rate-limiting, The kinetic equations have been derived and the constants of the individual reaction steps calculated, .