AB-INITIO GB STUDY OF CHEMICAL INTERMEDIATES IN SOLUTION - ETHYLENESULFONIUM ION IN HYDROLYSIS OF 2-CHLOROETHYL METHYL SULFIDE

Citation
O. Kikuchi et al., AB-INITIO GB STUDY OF CHEMICAL INTERMEDIATES IN SOLUTION - ETHYLENESULFONIUM ION IN HYDROLYSIS OF 2-CHLOROETHYL METHYL SULFIDE, Heteroatom chemistry, 9(5), 1998, pp. 503-510
Citations number
33
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Chemistry
Journal title
ISSN journal
1042-7163
Volume
9
Issue
5
Year of publication
1998
Pages
503 - 510
Database
ISI
SICI code
1042-7163(1998)9:5<503:AGSOCI>2.0.ZU;2-S
Abstract
Ab initio MO theory including solvent effects has been applied to the structure and reactivity of methyl ethylenesulfonium ion, 1, in aqueou s solution as a model of the three-membered cyclic sulfonium intermedi ate expected in the toxic action of sulfur mustard. The 6-31 + G geom etry optimization of the cyclic sulfonium ion 1 suggested that the rin g size of 1 is expanded slightly by solvation. The contour lines map o f the interaction energy between 1 and Cl- has a very shallow and wide well at 5-6 Angstrom distance from 1. This is the solvent-separated i on pair, and the contact ion pair was not found between 1 and Cl-. The calculated energy diagrams for the S(N)2-type reactions of 1 With Cl- , H2O, and OH- that give ring-opened compounds indicated the following : (1) The energy of the 1 + Cl- system is similar to that of chloroeth yl methyl sulfide (CEMS, 2), and the interconversion between 1 + Cl- a nd 2 occurs easily in aqueous solution. The 3-21 + G() and 6-31 + G* activation energies for the 2 --> 1 + Cl- reaction, 20-22 kcal/mol, ag ree well with the experimental enthalpy of activation for the hydrolys is of 2. (2) The reaction of 1 with OH- gives a very stable hydroxyl c ompound 4, and no transition state was found. (3) The reaction of 1 wi th H2O gives an unstable addition product that is expected to be conve rted to 4 with the assistance of another H2O molecule. This mechanism is consistent with that proposed by Bartlett and Swain in their pionee ring work on the hydrolysis of sulfur mustard. (C) 1998 John Wiley & S ons, Inc. Heteroatom Chem 9:503-510, 1998.