Steric factors in the gas phase elimination kinetics of ethyl N-benzyl-N-cyclopropylcarbamate and ethyl diphenylcarbamate

✍ Scribed by Marniev Luiggi; Rosa M. Dominguez; Alexandra Rotinov; Armando Herize; Mary Cordova; Gabriel Chuchani

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 126 KB
• Volume: 34
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.10010

✦ Synopsis

Abstract

The elimination kinetics of ethyl N‐benzyl‐N‐cyclopropylcarbamate and ethyl diphenylcarbamate were investigated over the temperature range of 349.9–440.0°C and the pressure range of 31–106 Torr. These reactions have been found to be homogeneous, unimolecular, and obey a first‐order rate law. The products are ethylene, carbon monoxide, and the corresponding secondary amine. The rate coefficient is expressed by the following Arrhenius equations:

For ethyl N‐benzyl‐N‐cyclopropylcarbamate

log k~1~ (s^−1^) = (12.94 ± 0.09) − (198.5 ± 0.9) kJ mol^−1^ (2.303RT)^−1^

For ethyl diphenylcarbamate

log k~1~ (s^−1^) = (12.91 ± 0.18) − (208.2 ± 2.4) kJ mol^−1^ (2.303RT)^−1^

The presence of phenyl and bulky groups at the nitrogen atom of the ethylcarbamate showed a decrease in the rate of elimination. Steric factor may be operating during the process of decomposition of these substrates. These reactions appear to undergo a semipolar six‐membered cyclic transition type of mechanism.© 2001 John Wiley & Sons, Inc. Int J Chem Kinet 34: 67–71, 2002