| New insight on the origin of the unusual acidity of Meldrum's acid from ab initio and combined QM/MM simulation study. | |
| | |
MedLine Citation:
|
PMID: 11457147 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
|
Ab initio molecular orbital and combined QM/MM Monte Carlo simulations have been carried out to investigate the origin of the unusually high acidity of Meldrum's acid. Traditionally, the high acidity of Meldrum's acid relative to that of methyl malonate has been attributed to an additive effect due to the presence of two E esters in the dilactone system. However, the present study reveals that there is significant nonadditive effect that also makes major contributions. This results from preferential stabilization of the enolate anion over that of Meldrum's acid due to anomeric stereoelectronic interactions. To investigate solvent effects on the acidity in aqueous solution, the relative acidities of Z and E conformers of methyl acetate have been determined in combined ab initio QM/MM simulations. There is significant solvent effect on the conformational equilibria for both the neutral ester and its enolate anion in water, leading to stabilization of the E stereoisomer. However, the computed solvent effect of 4.4 kcal/mol in favor of the E isomer of methyl acetate is largely offset by the favorable solvation of 3.4 kcal/mol for the E conformer of the enolate anion. This leads to an enhanced acidity of 3.4 kcal/mol for the (E)-methyl acetate in water over the Z conformer. In Meldrum's acid, it is the preferential stabilization of the enolate anion due to anomeric effects coupled with the intrinsically higher acidity of the E conformation of ester that is responsible for its high acidity. |
| | |
Authors:
|
K Byun; Y Mo; J Gao |
Related Documents
:
|
18484147 - Radioprotectant and radiosensitizer effects on sterility of gamma-irradiated bone. 21090647 - Building addressable libraries: the use of "safety-catch" linkers on microelectrode arr... 15884837 - Specificity of codling moth (lepidoptera: tortricidae) for the host plant kairomone, et... 18338867 - The chemical characterization of the aroma of dessert and sparkling white wines (pedro ... 12957167 - Method for the quantitative assay of fatty acid-bile acid conjugates by tandem mass spe... 7518747 - The structure of the o-specific polysaccharide of hafnia alvei strain 1216. |
Publication Detail:
|
Type: Journal Article; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S. |
Journal Detail:
|
Title: Journal of the American Chemical Society Volume: 123 ISSN: 0002-7863 ISO Abbreviation: J. Am. Chem. Soc. Publication Date: 2001 May |
Date Detail:
|
Created Date: 2001-07-17 Completed Date: 2001-08-23 Revised Date: 2006-11-15 |
Medline Journal Info:
|
Nlm Unique ID: 7503056 Medline TA: J Am Chem Soc Country: United States |
Other Details:
|
Languages: eng Pagination: 3974-9 Citation Subset: IM |
Affiliation:
|
Department of Chemistry and Minnesota Supercomputing Institute, University of Minnesota, 207 Pleasant Street S.E., Minneapolis, Minnesota 55455, USA. |
Export Citation:
|
APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
|
Acetates
/
chemistry Dioxanes / chemistry* Hydrogen-Ion Concentration Molecular Structure Quantum Theory Solvents Thermodynamics |
| Chemical | |
Reg. No./Substance:
|
0/Acetates; 0/Dioxanes; 0/Solvents; 2033-24-1/Meldrum's acid; 79-20-9/methyl acetate |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
Previous Document: New mode of coordination for the dinitrogen ligand: formation, bonding, and reactivity of a tantalum...
Next Document: The reaction of protonated dimethyl ether with dimethyl ether: temperature and isotope effects on th...