The Energy of the C–H Bond in the Three Picolines (Methyl Pyridines)

Abstract

The pyrolysis of the three picolines was investigated and the rates of the decomposition were compared with the rate of the decomposition of toluene. It was found that the process of the decomposition of the picolines is analogous to that of toluene, i.e., the rate determining step is the splitting of the picoline molecule into H atom and a picolyl radical. Comparison of the decomposition rates of the picolines and of toluene made it possible to calculate the C–H bond energy for these compounds. These were estimated at 75.5 kcal./mole for α‐picoline, 76.5 kcal./mole for β‐picoline, and 77.5 kcal./mole for γ‐picoline. It was concluded therefore that the resonance energy of the picolyl radical approximates within a few kcal. the resonance energy of the benzyl radical.