ISSN:
0894-3230
Schlagwort(e):
Organic Chemistry
;
Physical Chemistry
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Physik
Notizen:
The kinetics of the elimination of several polar 2-substituted ethyl methanesulphonates in the gas phase were determined in a static system, seasoned with allylbromide, and in the presence of at least equal amount of the freeradical suppressor propene and/toluene. The working temperature and pressure ranges were 290-360°C and 31°199 Torr (1 Torr = 133.3 Pa), respectively. The reactions are homogeneous, unimolecular, show a first-order rate law and take place according to the following equations: for 3-chloropropyl methanesulphonate, log k1 (s-1) = (12.01 ± 0.18) - (171.7 ± 2.1) kJ mol-1 (2.303RT)-1; for 4-chlorobutyl methanesulphonate, log k1 (S-1) = (11.78 ± 0.31) - (166.1 ± 3.5) kJ mol-1 (2.303RT)-1; for 3-methoxypropyl methanesulphonate, log k1 (s-1) = (11.50 ± 0.36) - (163.3 ± 4.0) kJ Mol-1 (2.303RT)-1; and for 2-ethoxyethyl methanesulphonate, log k1 (s-1) = (11.52 ± 0.37) - (167.3 ± 4.1) kJ mol-1 (2.303RT)-1. The present data together with those reported in the literature show that alkyl 2-substituted ethyl methanesulphonates give an approximate straight line when log k/ko vs σ* values (ρ* = -0.82 ± 0.088, intercept = 0.0084 ± 0.0209 and correlation coefficient r = 0.967 at 320°C) are plotted. However, polar substituents at the 2-position of ethyl methanesulphonates give rise to an inflection point at σ*(CH3) = 0.00 into another very good straight line (σ* = -0.29 ± 0.013, intercept = -0.0065 ± 0.0213 and r = 0.994 at 320°C). The mechanism of these reactions is considered to be heterolytic in nature, proceeding in terms of an intimate ion-pair intermediate.
Zusätzliches Material:
2 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/poc.610040702
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