Nitrosation of 2-hydroxyethylpiperidine

The kinetics of the nitrosation of 2-hydroxyethylpiperidine have been studi ed in acidic (0.05-0.30 mol dm(-3) HClO4) aqueous media. The reaction rate is first order with respect to nitrite and amine and independent of acidity and shows an experimental isotope effect of 1.73. The most plausible mecha nism involves the fast formation of an alkyl nitrite in the protonated amin e (equilibrium constant estimated as 0.014 dm(3) mol(-1)). The loss of a pr oton from this intermediate is the rate-limiting step, and it is followed b y a fast internal nitroso group transfer from the oxygen to the nitrogen at om to give the corresponding N-nitroso compound. A comparison of this nitro sation pathway of secondary amines in acid media with the nitrosation of th iomorpholine and piperidine, and with that of amines by alkyl nitrites in b asic media is also discussed.