ISSN:
0538-8066
Schlagwort(e):
Chemistry
;
Physical Chemistry
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
The gas-phase elimination of several polar substituents at the α carbon of ethyl acetates has been studied in a static system over the temperature range of 310-410°C 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 k1 (s-1) = (12.88 ± 0.29) - (203.3 ± 2.6) kJ/mol (2.303RT)-1; for 3-acetoxy-2-butanone, log ±1(s-1) = (13.40 ± 0.20) - (202.8 ± 2.4) kJ/mol (2.303RT)-1; for 1,1,1-trichloro-2-acetoxypropane, log ℜ1 (s-1) = (12.12 ± 0.50) - (193.7 ± 6.0) kJ/mol (2.303RT)-; for methyl 2-acetoxypropionate, log ℜ1 (s-1) = (13.45 ± 0.05) - (209.5 ± 0.5) kJ/mol (2.303RT)-1; for 1-chloro-2-acetoxypropane, log ℜ1 (s-1) = (12.95 ± 0.15) - (197.5 ± 1.8) kJ/mol (2.303RT)-1; for 1-fluoro-2-acetoxypropane, log ℜ1 (s-1) = (12.83 ± 0.15)- (197.8 ± 1.8) kJ/mol (2.303RT)-1; for 1-dimethylamino-2-acetoxypropane, log ℜ1 (s-1) = (12.66 ± 0.22) -(185.9 ± 2.5) kJ/mol (2.303RT)-1; for 1-phenyl-2-acetoxypropane, log ℜ1 (s-1) = (12.53 ± 0.20) - (180.1 ± 2.3) kJ/mol (2.303RT)-1; and for 1-phenyl-3-acetoxybutane, log ℜ1 (s-1) = (12.33 ± 0.25) - (179.8 ± 2.9) kJ/mol (2.303RT)-1. The Cα—O 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 σ bonds have been projected and discussed. The present work may provide a general view on the effect of alkyl and polar substituents at the Cα—O bond in the gas-phase elimination of secondary acetates.
Zusätzliches Material:
4 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/kin.550150302
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