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Gas‐Phase Kinetics of the Pyrolysis of Some 3,3‐Dimethyl‐1‐(trimethylsilyl)‐cyclopropenes — Unexpected Product Distribution in the Cyclopropene Rearrangement
Author(s) -
Walsh Robin,
Untiedt Sven,
Meijere Armin De
Publication year - 1994
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19941270134
Subject(s) - cyclopropene , chemistry , trimethylsilyl , diradical , product distribution , medicinal chemistry , gas phase , photochemistry , computational chemistry , organic chemistry , catalysis , physics , nuclear physics , singlet state , excited state
The gas‐phase pyrolyses of 1,3,3‐trimethyl‐2‐(trimethylsilyl)‐cyclopropene ( 9 ), 3,3‐dimethyl‐1,2‐bis(trimethylsilyl)cyclopropene TextReactant log ( A /s −1 ) E a /kj mol −1 (kcal mol −1 )9 13.41 ± 0.22 192.1 ± 2.5 (45.9 ± 0.6)10 13.54 ± 0.19 184.4 ± 2.1 (44.1 ± 0.5)11 12.17 ± 0.38 124.6 ± 3.1 (29.8 ± 0.7)( 10 ), and 3,3‐dimethyl‐1‐(methylthio)‐2‐(trimethylsilyl)cyclopropene ( 11 ) have been studied, and the pressure‐independent Arrhenius parameters listed in the table were obtained. All three rearrangements are homogeneous, first‐order and unimolecular reactions. Rather surprisingly all reactions give the corresponding isomeric allenes as the main products. Amongst possible mechanisms discussed, 10 is proposed to react via a cyclopropylidene intermediate, whilst the results for 9 and 11 throw light on the relative importance of the diradical‐ and vinylcarbene‐type intermediates produced by cyclopropene ring opening.