Document Detail


Probing Acidity of Carboxylic Acids in Protic Ionic Liquids, Water and their Binary Mixtures: Activation Energy of Proton Transfer.
MedLine Citation:
PMID:  23373464     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Acidity functions were used to express the ability of a solvent/solution to donate/accept proton to a solute. The present work accounts for the acidity determination of HCOOH, CH3COOH and CH3CH2COOH in the alkylimidazolium-based protic ionic liquids (PILs), incorporated with carboxylate anion, water and in binary mixture of PIL and water using Hammett acidity function, Ho. A reversal in the acidity trend was observed, when organic acids were transferred from water to PIL. It was emphasized that an increased stabilization offered by PIL cation towards the more basic conjugate anion of organic acid was responsible for this anomalous change in acidity order in PILs, which was absent in water. The greater stabilization of a basic organic anion by PIL cation is discussed in terms of the stable hard-soft acid base (HSAB) pairing. A change in the Ho values of these acids was observed with a change in temperature and a linear correlation between the ln Ho and 1/T was noted. This relationship points toward the activation energy of proton transfer (EaH+), a barrier provided by the medium during the proton transfer from Brønsted acid to indicator. The Ho function in binary mixtures points to the involvement of pseudo-solvent, the behavior of which changes with the nature and concentration of acid. The presence of the maxima/minima in Ho function is discussed in terms of the synergetic behavior of the pseudo-solvent composed of the mixtures of aqueous PILs.
Authors:
Shashi Kant Shukla; Anil Kumar
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-2-1
Journal Detail:
Title:  The journal of physical chemistry. B     Volume:  -     ISSN:  1520-5207     ISO Abbreviation:  J Phys Chem B     Publication Date:  2013 Feb 
Date Detail:
Created Date:  2013-2-4     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101157530     Medline TA:  J Phys Chem B     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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