Next Article in Journal
Synthesis of Polyamidoamine Dendrimer for Encapsulating Tetramethylscutellarein for Potential Bioactivity Enhancement
Previous Article in Journal
Isolation and Culture of Pig Spermatogonial Stem Cells and Their in Vitro Differentiation into Neuron-Like Cells and Adipocytes
Article Menu
Issue 11 (November) cover image

Export Article

Open AccessArticle
Int. J. Mol. Sci. 2015, 16(11), 26347-26362; doi:10.3390/ijms161125959

Gas-Phase Thermal Tautomerization of Imidazole-Acetic Acid: Theoretical and Computational Investigations

1,†
,
1,2,†,* , 1,3,†
and
1,4,†
1
Chemistry Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia
2
Chemistry Department, Faculty of Science, University of Khartoum, P.O. Box 321, Khartoum 11111, Sudan
3
Chemistry Department, Faculty of Science, Beni-Suef University, Beni-Suef 62511, Egypt
4
Chemistry Department, Faculty of Science, Cairo University, Giza 12613, Egypt
These authors contributed equally to this work.
*
Author to whom correspondence should be addressed.
Academic Editor: Henry Chermette
Received: 7 August 2015 / Revised: 10 October 2015 / Accepted: 22 October 2015 / Published: 4 November 2015
(This article belongs to the Section Physical Chemistry, Theoretical and Computational Chemistry)
View Full-Text   |   Download PDF [3331 KB, uploaded 4 November 2015]   |  

Abstract

The gas-phase thermal tautomerization reaction between imidazole-4-acetic (I) and imidazole-5-acetic (II) acids was monitored using the traditional hybrid functional (B3LYP) and the long-range corrected functionals (CAM-B3LYP and ωB97XD) with 6-311++G** and aug-cc-pvdz basis sets. The roles of the long-range and dispersion corrections on their geometrical parameters, thermodynamic functions, kinetics, dipole moments, Highest Occupied Molecular Orbital–Lowest Unoccupied Molecular Orbital (HOMO–LUMO) energy gaps and total hyperpolarizability were investigated. All tested levels of theory predicted the preference of I over II by 0.750–0.877 kcal/mol. The origin of predilection of I is assigned to the H-bonding interaction (nN8→σ*O14H15). This interaction stabilized I by 15.07 kcal/mol. The gas-phase interconversion between the two tautomers assumed a 1,2-proton shift mechanism, with two transition states (TS), TS1 and TS2, having energy barriers of 47.67–49.92 and 49.55–52.69 kcal/mol, respectively, and an sp3-type intermediate. A water-assisted 1,3-proton shift route brought the barrier height down to less than 20 kcal/mol in gas-phase and less than 12 kcal/mol in solution. The relatively high values of total hyperpolarizability of I compared to II were interpreted and discussed. View Full-Text
Keywords: imidazole-4-acetic acid; tautomerization; long-range; dispersion imidazole-4-acetic acid; tautomerization; long-range; dispersion
Figures

Figure 1

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

Supplementary material

Scifeed alert for new publications

Never miss any articles matching your research from any publisher
  • Get alerts for new papers matching your research
  • Find out the new papers from selected authors
  • Updated daily for 49'000+ journals and 6000+ publishers
  • Define your Scifeed now

SciFeed Share & Cite This Article

MDPI and ACS Style

Aziz, S.G.; Osman, O.I.; Elroby, S.A.; Hilal, R.H. Gas-Phase Thermal Tautomerization of Imidazole-Acetic Acid: Theoretical and Computational Investigations. Int. J. Mol. Sci. 2015, 16, 26347-26362.

Show more citation formats Show less citations formats

Related Articles

Article Metrics

Article Access Statistics

1

Comments

[Return to top]
Int. J. Mol. Sci. EISSN 1422-0067 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top