Armando Herize

Neighbouring group participation in the gas‐phase pyrolysis kinetics of 4‐(N‐methyl‐N‐phenylamino)‐1‐butyl acetate and 4‐(N‐phenylamino)‐1‐butyl acetate

The pyrolysis kinetics of two phenylaminobutyl acetates were determined in a static system over the temperature range 359.7–399.6 °C and the pressure range 23.8–95 Torr. The reactions, in vessels seasoned with allyl bromide and in the presence of the free radical inhibitor toluene, are homogeneous and unimolecular, and obey a first-order rate law. The overall rate coefficients are expressed by the following equations: for 4-(N-methyl-N-phenylamino)-1-butyl acetate, log[k1 (s−1)] = (13.92 ± 0.36) − (210.4 ± 4.5) kJ mol−1 (2.303RT)−1; and for 4-(N-phenylamino)-1-butyl acetate, log[k1 (s−1)] = (12.03 ± 0.43) − (188.3 ± 5.3) kJ mol−1 (2.303RT)−1. The decomposition of these substrates undergoes a parallel reaction. The predominant primary product, the corresponding heterocyclic product, appears to be the result of an anchimeric assistance of the amino substituent for a back-side displacement. This suggests that an incipient ion-pair type of mechanism may be operating during the process of elimination. The Arrhenius expressions for the parallel decomposition of each of the aminobutyl acetate substrates are presented and discussed. Copyright