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

J G Buchanan, M H Charlton, M F Mahon, J J Robinson, G D Ruggiero, I H Williams

Research output: Contribution to journalArticle

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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.
Original languageEnglish
Pages (from-to)642-646
Number of pages5
JournalJournal of Physical Organic Chemistry
Volume15
Issue number9
DOIs
Publication statusPublished - 2002

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Lactones
Pulse code modulation
rings
critical point
water
aqueous solutions
maleates
Water
bromine
acrylates
Bromine
Fumarates
adducts
Electronic density of states
Molecules
density distribution
molecules
isomers
Isomers
anions

Cite this

Experimental and computational studies of alpha-lactones: Structure and bonding in the three-membered ring. / Buchanan, J G; Charlton, M H; Mahon, M F; Robinson, J J; Ruggiero, G D; Williams, I H.

In: Journal of Physical Organic Chemistry, Vol. 15, No. 9, 2002, p. 642-646.

Research output: Contribution to journalArticle

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