The elimination kinetics and mechanisms of ethyl piperidine‐3‐carboxylate, ethyl 1‐methylpiperidine‐3‐carboxylate, and ethyl 3‐(piperidin‐1‐yl)propionate in the gas phase

The gas-phase elimination kinetics of the above-mentioned compounds were determined in a static reaction system over the temperature range of 369–450.3°C and pressure range of 29–103.5 Torr. The reactions are homogeneous, unimolecular, and obey a first-order rate law. The rate coefficients are given by the following Arrhenius expressions: ethyl 3-(piperidin-1-yl) propionate, log k1(s−1) = (12.79 ± 0.16) − (199.7 ± 2.0) kJ mol−1 (2.303 RT)−1; ethyl 1-methylpiperidine-3-carboxylate, log k1(s−1) = (13.07 ± 0.12)–(212.8 ± 1.6) kJ mol−1 (2.303 RT)−1; ethyl piperidine-3-carboxylate, log k1(s−1) = (13.12 ± 0.13) − (210.4 ± 1.7) kJ mol−1 (2.303 RT)−1; and 3-piperidine carboxylic acid, log k1(s−1) = (14.24 ± 0.17) − (234.4 ± 2.2) kJ mol−1 (2.303 RT)−1. The first step of decomposition of these esters is the formation of the corresponding carboxylic acids and ethylene through a concerted six-membered cyclic transition state type of mechanism. The intermediate β-amino acids decarboxylate as the α-amino acids but in terms of a semipolar six-membered cyclic transition state mechanism. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 38: 106–114, 2006

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