ISSN:
1572-9001
Keywords:
Sulfonium ion
;
carboxylate hydration
;
water complexes
;
ab initio
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract The interactions of the sulfonium ions (CH3)3S+, (CH3)2S+CH2CO2 −, and (CH3)2S+-CH2CH2CO2 − with up to four water molecules have been studied by ab initio molecular orbital methods. Complexes of (CH3)3S+ with one to three water molecules involve strong electrostatic sulfur-oxygen interactions; in contrast, the sulfide (CH3)2S interacts with water molecules via weak S-H hydrogen bonds, suggesting that methyl-group transfer from (CH3)3S+ in aqueous solution involves a significant alteration of the hydration pattern around the sulfur atom. Two conformers of (CH3)2S+CH2CO2 − were found that display sulfur-oxygen distances which are approximately 0.3 å less than the sum of the sulfur and oxygen van der Waals radii, indicating a strong intramolecular electrostatic interaction. For the complexes (CH3)2S+CH2CO2 −·nH2O(n =1–4), water interacts primarily with the carboxylate group via hydrogen bonds, rather than electrostatically with the sulfur atom, although in complexes with the three- and four-water complexes, the proximity of the positively charged sulfur atom to the carboxylate group significantly alters the hydration pattern compared to that in the corresponding of complexes CH3SCH2CO2 −· Thus, methyl transfer from (CH3)2S+CH2CO2 − to an acceptor in aqueous solution also involves substantial changes in the hydration pattern around the carboxylate group.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02254844
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