ISSN:
0538-8066
Keywords:
Chemistry
;
Physical Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Ethyl 4-chlorobutyrate, which is reexamined, pyrolyzes at 350-410°C to ethylene, butyrolactone, and HCl. Under the reaction conditions, the primary product 4-chlorobutyric acid is responsible for the formation of γ-butyrolactone and HCl. In seasoned vessels, and in the presence of a free-radical inhibitor, the ester elimination is homogeneous, unimolecular, and follows a first-order rate law. For initial pressures from 69-147 Torr, the rate is given by the following Arrhenius expression: log k1(s-1) = (12.21 ± 0.26) - (197.6 ± 3.3) kJ mol-1 (2.303RT)-1. The rates and product formation differ from the previous work on the chloroester pyrolysis.4-Chlorobutyric acid, an intermediate product of the above substrate, was also pyrolyzed at 279-330°C with initial pressure within the range of 78-187 Torr. This reaction, which yields γ-butyrolactone and HCl, is also homogeneous, unimolecular, and obeys a first-order rate law. The rate coefficient, is given by the following Arrhenius equation: log k1(s-1) = (12.28 ± 0.41) - (172.0 ± 4.6) kJ mol-1 (2.303RT)-1. The pyrolysis of ethyl chlorobutyrate proceeds by the normal mechanism of ester elimination. However, the intermediate 4-chlorobutyric acid was found to yield butyrolactone through anchimeric assistance of the COOH group and by an intimate ion pair-type of mechanism. Additional evidence of cyclic product and neighboring group participation is described and presented.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/kin.550190902
