Document Detail


Kinetics and mechanism of oxidation of N, N'-dimethylaminoiminomethanesulfinic acid by acidic bromate.
MedLine Citation:
PMID:  18714963     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The major metabolites of the physiologically active compound dimethylthiourea (DMTU), dimethylaminoiminomethansesulfinic acid (DMAIMSA), and dimethylaminoiminomethanesulfonic acid (DMAIMSOA) were synthesized, and their kinetics and mechanisms of oxidation by acidic bromate and aqueous bromine was determined. The oxidation of DMAIMSA is much more facile and rapid as compared to a comparable oxidation by the same reagents of the parent compound, DMTU. The stoichiometry of the bromate-DMAIMSA reaction was determined to be 2BrO 3 (-) + 3NHCH 3(NCH 3)CSO 2H + 3H 2O --> 3SO 4 (2) (-) + 2Br (-) + 3CO(NHCH 3) 2 + 6H (+), with quantitative formation of sulfate. In excess bromate conditions, the stoichiometry was 4BrO 3 (-) + 5NHCH 3(NCH 3)CSO 2H + 3H 2O --> 5SO 4 (2) (-) + 2Br 2 + 5CO(NHCH 3) 2 + 6H (+). The direct bromine-DMAIMSA reaction gave an expected stoichiometric ratio of 2:1 with no further oxidation of product dimethylurea (DMU) by aqueous bromine. The bromine-DMAIMSA reaction was so fast that it was close to diffusion-controlled. Excess bromate conditions delivered a clock reaction behavior with the formation of bromine after an initial quiescent period. DMAIMSOA, on the other hand, was extremely inert to further oxidation in the acidic conditions used for this study. Rate of consumption of DMAIMSA showed a sigmoidal autocatalytic decay. The postulated mechanism involves an initial autocatalytic build-up of bromide that fuels the formation of the reactive oxidizing species HBrO 2 and HOBr through standard oxybromine reactions. The long and weak C-S bond in DMAIMSA ensures that its oxidation goes directly to DMU and sulfate, bypassing inert DMAIMSOA.
Authors:
Adenike A Otoikhian; Reuben H Simoyi
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2008-08-20
Journal Detail:
Title:  The journal of physical chemistry. A     Volume:  112     ISSN:  1520-5215     ISO Abbreviation:  J Phys Chem A     Publication Date:  2008 Sep 
Date Detail:
Created Date:  2008-09-12     Completed Date:  2008-11-17     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9890903     Medline TA:  J Phys Chem A     Country:  United States    
Other Details:
Languages:  eng     Pagination:  8569-77     Citation Subset:  IM    
Affiliation:
Department of Chemistry, Portland State University, Portland, Oregon 97207-0751, USA.
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MeSH Terms
Descriptor/Qualifier:
Acids / chemistry
Bromates / chemistry*
Kinetics
Methylamines / chemical synthesis,  chemistry*
Models, Chemical*
Models, Molecular
Oxidation-Reduction
Sulfinic Acids / chemical synthesis,  chemistry*
Thiourea / analogs & derivatives,  chemical synthesis,  chemistry
Time Factors
Chemical
Reg. No./Substance:
0/Acids; 0/Bromates; 0/Methylamines; 0/N,N'-dimethylaminoiminomethanesulfinic acid; 0/Sulfinic Acids; 61805-96-7/1,3-dimethylthiourea; 62-56-6/Thiourea

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