The kinetics of the nitrosation of piperidine by propyl,iso-propyl, butyl,iso-butyl,sec-butyl, andtert-butyl nitrites in 0.1MNaOH and of the hydrolysis of the nitrite esters were studied spectrophotometrically by monitoring the absorbance of the nitrites at 381 nm. The observed correlation between logk2and σ* (ρ*=4.5) shows the reaction to proceedviaelectrophilic attack by the nitrites; the existence of an isokinetic relationship suggests a single mechanism for the whole series. Comparison of the relative reactivities of the alkyl nitrites (primary>secondary>tertiary) with characteristic parameters of theirRgroups (vertical ionization potentials and heats of formation ofR+) suggests that these reactions are orbital controlled. All hydrolysis reactions were slower than the corresponding aminolysis reactions. This is attributed to a retardation of the former reaction by unfavourable interactions between the lone pairs of the nucleophile and the nitroso nitrogen ato