Kinetics of elimination of several heterocyclic carbamates in the gas phase

The kinetics of the gas‐phase elimination of several heterocyclic carbamates were determined in a static system over the temperature range 190.0–409.7 °C and the pressure range 26.5–125 Torr (1 Torr = 133.3 Pa). The reactions in seasoned vessels, with the free radical inhibitor cyclohexene and/or toluene always present, are homogeneous and unimolecular and obey a first‐order rate law. The observed rate coefficients are represented by the following Arrhenius equations: for tert ‐butyl‐1‐pyrrolidine carboxylate, log k 1 (s −1 ) = (11.36 ± 0.31) −(145.4 ± 3.1)kJ mol −1 (2.303 RT ) −1 ; for 1‐( tert ‐butoxycarbonyl)‐2‐pyrrolidinone, log k 1 (s −1 ) = (11.54 ± 0.29) −(140.8 ± 2.8)kJ mol −1 (2.303 RT ) −1 ; for tert ‐butyl‐1‐pyrrole carboxylate, log k 1 (s −1 ) = (12.12 ± 0.05) −(145.2 ± 1.0) kJ mol −1 (2.303 RT ) −1 ; and for 1‐ethylpiperazine carboxylate, log k 1 (s −1 ) = (12.05 ± 0.19) −(188.2 ± 4.6) kJ mol −1 (2.303 RT ) −1 . The saturated heterocyclic carbamates show a decrease in rates of elimination due to electronic factors. Heterocyclic carbamates with a nitrogen atom able to delocalize its electrons with π‐bonds present in the ring were found to enhance the rates due to resonance interactions. Copyright © 2002 John Wiley & Sons, Ltd.