Document Detail

The standard pKa scales of carbon-centered indicator acids in ionic liquids: Effect of media and structural implication.
MedLine Citation:
PMID:  22860575     Owner:  NLM     Status:  Publisher    
Energetics of bond dissociation, especially the R-H bond heterolysis free energy (pKa), has played a central role in promoting chemistry to become a rational science. Despite the oceans of acidity studies in literature, the current knowledge is much limited to the classical molecular solvents and is unable to be extended to anticipate the acidity changes in ionic media. As the latter is now very popular for replacing volatile organic solvents, it becomes highly desirable to know how the driving force of bond breaking is varied as the medium composition switched from molecules to ions. Here we describe a general approach to measure absolute pKa's in pure ionic liquid (IL). The standard conditions warranting accurate measurement were outlined. The pKa's of the selected 18 C-H type indicator acids in four ILs were determined and a convenient indicator platform was constructed for easy expansion of acidity scales. These absolute pKa'`s make possible, for the first time, direct comparisons of bond strengths in IL with those in molecular solvent and the gas phase, and should be able to serve as standard parameters for calibrating computational methods suitable for the studies in ionic media. The effect of cation and anion in IL in relation to structure was analyzed.
Hui Deng; Xin Li; Yuan Chu; Jiaqi He; Jin-Pei Cheng
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-8-3
Journal Detail:
Title:  The Journal of organic chemistry     Volume:  -     ISSN:  1520-6904     ISO Abbreviation:  J. Org. Chem.     Publication Date:  2012 Aug 
Date Detail:
Created Date:  2012-8-6     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  2985193R     Medline TA:  J Org Chem     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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