Document Detail


An Ionic Liquid Dependent Mechanism for Base Catalyzed β-Elimination Reactions from QM/MM Simulations.
MedLine Citation:
PMID:  23273322     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Ionic liquids have been proposed to induce a mechanistic change in the reaction pathway for the fundamentally important base-induced β-elimination class compared to conventional solvents. The role of the reaction medium in the elimination of 1,1,1-tribromo-2,2-bis(3,4-dimethoxyphenyl)ethane via two bases, piperidine and pyrrolidine, has been computationally investigated using methanol and the ionic liquids 1-butyl-3-methylimidazolium tetrafluoroborate and hexafluorophosphate [BMIM][BF4] and [BMIM][PF6], respectively. QM/MM Monte Carlo simulations utilizing free-energy perturbation theory found the ionic liquids did produce a reaction pathway change from an E1cB-like mechanism in methanol to a pure E2 route that is consistent with experimental observations. The origin of the ionic liquid effect has been found as: (1) a combination of favorable electrostatic interactions, e.g., bromine-imidazolium ion, and (2) π-π interactions that enhance the coplanarity between aromatic rings maximizing the electronic effects exerted on the reaction route. Solute-solvent interaction energies have been analyzed and show that liquid clathrate solvation of the transition state is primarily responsible for the observed mechanistic changes. This work provides the first theoretical evidence of an ionic liquid dependent mechanism and elucidates the interplay between sterics and electrostatics crucial to understanding the effect of these unique solvents upon chemical reactions.
Authors:
Caley Allen; Somisetti V Sambasivarao; Orlando Acevedo
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-12-31
Journal Detail:
Title:  Journal of the American Chemical Society     Volume:  -     ISSN:  1520-5126     ISO Abbreviation:  J. Am. Chem. Soc.     Publication Date:  2012 Dec 
Date Detail:
Created Date:  2012-12-31     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7503056     Medline TA:  J Am Chem Soc     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Export Citation:
APA/MLA Format     Download EndNote     Download BibTex
MeSH Terms
Descriptor/Qualifier:

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


Previous Document:  Modic changes of the cervical spine in patients with whiplash injury: A prospective 11-year follow-u...
Next Document:  Diagnostic accuracy of quantitative angiographic and intravascular ultrasound parameters predicting ...