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Experimental and computational studies of alpha-lactones: Structure and bonding in the three-membered ring


Reference:

Buchanan, J. G., Charlton, M. H., Mahon, M. F., Robinson, J. J., Ruggiero, G. D. and Williams, I. H., 2002. Experimental and computational studies of alpha-lactones: Structure and bonding in the three-membered ring. Journal of Physical Organic Chemistry, 15 (9), pp. 642-646.

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Abstract

Crystallographic analysis of the bromo-beta-lactones obtained by addition of bromine to aqueous solutions of disodium 2,3-dimethylmaleate and 2,3-dimethylfumarate reveals stereochernistries (4 from 1, and 3 from 2) opposite to those originally assigned (3 from 1, and 4 from 2). Specifically, the maleate leads to a bromo-beta-lactone with the methyl groups in a trans relationship, whereas the fumarate leads to the corresponding cis isomer. To account for this observation, we suggest that the first-formed intermediate in each case is an alpha-lactone. B3LYP/6-31 + G(d) calculations in PCM water indicate that the cyclic chloronium and bromonium adducts of acrylate anion are not intermediates but transition structures for the degenerate rearrangement of halomethyl-alpha-lactones. Bader analysis of MP2/6-31 + G(d,p) electron density distributions indicates that oxiranone possesses considerable ionic character in the endocyclic C-alpha-O-n bond. In PCM water there is neither a ring critical point nor a bond critical point for C-alpha-O-n, although geometrically the molecule still possesses an acute-angled three-membered ring with a C-alpha-C-n angle of only 69degrees. Combined quantum/classical calculations for B3LYP/6-31 + G(d) oxiranone surrounded by about 600 explicit TIP3P water molecules indicate that the cyclic structure is an energy minimum in aqueous solution, and Bader analysis gives a result similar to that from the continuum model. Copyright (C) 2002 John Wiley Sons, Ltd.

Details

Item Type Articles
CreatorsBuchanan, J. G., Charlton, M. H., Mahon, M. F., Robinson, J. J., Ruggiero, G. D. and Williams, I. H.
DOI10.1002/poc.526
DepartmentsFaculty of Science > Chemistry
RefereedYes
StatusPublished
ID Code5158
Additional InformationID number: ISI:000177633600005

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