ISSN:
0894-3230
Keywords:
Organic Chemistry
;
Physical Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
The gas-phase unimolecular elimination of the methanesulphonates in the temperature range 289.0-331.4°C and pressure range 18-152.5 Torr follows a first-order rate law. The rate coefficients for the homogeneous reactions are expressed by the following equations: for 3-(o-methoxyphenyl)propyl-1-methanesulphonate log[k1(s-1)] = (12.04 ± 0.32) - [(167.8 ± 3.6) kJ mol-1] (2.303RT)-1 and for 4-(p-methoxyphenyl)butyl-1-methanesulphonate log [k1(s-1)] = (12.82 ± 0.30) - [(175.1 ± 3.4) kJ mol-1] (2.303RT)-1. The oxygen atom of the CH3O substituent in 3-(o-methoxyphenyl)propyl-1-methanesulphonate appears to participate directly in the C-O bond polarization in order to produce some of the cyclic product dihydrobenzopyran. A parallel reaction occurs with 4-(p-methoxyphenyl)butyl-1-methanesulphonate where the p-anisyl substituent participates in the elimination process through a five-membered spiro intermediate for the formation of the cyclic product 6-methoxy-1,2,3,4-tetrahydronaphthalene. The second pathway of this elimination takes place via normal formation of the corresponding unsaturated aromatic hydrocarbons. These reactions are interpreted in terms of an intimate ion-pair type of mechanism.
Additional Material:
10 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/poc.610051103
