Journal
JOURNAL OF PHYSICAL ORGANIC CHEMISTRY
Volume 24, Issue 3, Pages 229-240Publisher
WILEY
DOI: 10.1002/poc.1733
Keywords
4-chlorobutan-2-one; 5-chloropentan-2-one and 4-chloro-1-phenylbutan-1-one; DFT and MP2 calculations; gas-phase elimination
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Funding
- Consejo de Desarrollo Cientifico y Humanistico (CDCH) [PG-03-00-6499-2006]
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The gas-phase elimination of kinetics 4-chlorobutan-2-one, 5-chloropentan-2-one, and 4-chloro-1-phenylbutan-1-one has been studied using electronic structure methods: B3LYP/6-31 G(d,p), B3LYP/6-31++G(d,p), MPW91PW91/6-31G(d,p), MPW91PW91/6-31++G(d,p), PBEPBE/6-31G(d,p), PBEPBE /6-31++G(d,p), and MP2/6-31++G(d,p). The above-mentioned substrates produce hydrogen chloride and the corresponding unsaturated ketone. Calculation results of 4-chlorobutan-2-one suggest a non-synchronous four-membered cyclic transition state (TS) type of mechanism. However, in the case of 5-chloropentan-2-one and 4-chloro-1-phenylbutan-1-one, the carbonyl group assists anchimerically through a polar five-membered cyclic TS mechanism. The polarization of the C-CI bond, in the sense of C delta+...C delta-, is a rate-determining step in these elimination reactions. The significant increase in rates in the elimination of 5-chloropentan-2-one and 4-chloro-1-phenylbutan-1-one is attributed to neighboring group participation due to the oxygen of the carbonyl group assisting the C-CI bond polarization in the TS. Copyright (C) 2010 John Wiley & Sons, Ltd.
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