Gas-phase elimination kinetics of 1-substituted ethyl acetates. Effect of polar substituents at the α carbon of secondary acetates

✍ Scribed by José A. Hernández A.; Gabriel Chuchani

• Book ID: 102926658
• Publisher: John Wiley and Sons
• Year: 1983
• Tongue: English
• Weight: 618 KB
• Volume: 15
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550150302

✦ Synopsis

The gas-phase elimination of several polar substituents a t the N carbon of ethyl acetates has been studied in a static system over the temperature range of 31O41O0C and the pressure range of 39-313 torr. These reactions are homogeneous in both clean and seasoned vessels, follow a first-order rate law, and are unimolecular. The temperature dependence of the rate coefficients is given by the following Arrhenius equations: 2-acetoxypropionitrile, log kl (s-l)

= (13.40 f 0.20) -(202.8 f 2.4) kJ/mol (2.303RT)-'; for l,l,l-trichloro-2-acetoxypropane, log hl (s-l) = (12.12 f 0.50) -(193.7 f 6.0) kJ/mo1(2.303RT)-'; for methyl 2-acetoxypropionate, log k l (s-l) = (13.45 f 0.05) -(209.5 f 0.5) kJ/mol (2.303RT)-I; for 1-chloro-2-acetoxypropane, log kl (S-I) = (12.95 f 0.15) -(197.5 f 1.8) kJ/mol (2.303RT)-I; for l-fluoro-2-acetoxypropane, log k l (s-') = (12.83 f 0.15) -(197.8 f 1.8) kJ/mol (2.303RT)-'; for 1dimethylamino-2-acetoxypropane, log k l (s-') = (12.66 f 0.22) -(185.9 f 2.5) kJ/mol (2.303RT)-'; for l-phenyl-2-acetoxypropane, log h1 (s-') = (12.53 f 0.20) -(180.1 f 2.3) kJ/mol(2.303RT)-'; and for l-phenyl-3-acetoxybutane, log kl (s-l) = (12.33 f 0.25) -(179.8 f 2.9) kJ/mol(2.303RT)-'. The C,-0 bond polarization appears to be the rate-determining process in the transmition state of these pyrolysis reactions. Linear correlations of electron-releasing and electron-withdrawing groups along strong u bonds have been projected and discussed. The present work may provide a general view on the effect of alkyl and polar substituents a t the C,,-0 bond in the gas-phase elimination of secondary acetates.