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Tautomerization, acidity, basicity, and stability of cyanoform: a computational study

BACKGROUND: Cyanoform is long known as one of the strongest acid. Cyanoform is only stable below −40 °C. The issue of the stability and tautomeric equilibria of cyanoform (CF) are investigated at the DFT and MP2 levels of theory. The present work presents a detailed study of structural tautomer inte...

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Autor principal: Elroby, Shaaban A.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Springer International Publishing 2016
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4828767/
https://www.ncbi.nlm.nih.gov/pubmed/27073411
http://dx.doi.org/10.1186/s13065-016-0166-z
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author Elroby, Shaaban A.
author_facet Elroby, Shaaban A.
author_sort Elroby, Shaaban A.
collection PubMed
description BACKGROUND: Cyanoform is long known as one of the strongest acid. Cyanoform is only stable below −40 °C. The issue of the stability and tautomeric equilibria of cyanoform (CF) are investigated at the DFT and MP2 levels of theory. The present work presents a detailed study of structural tautomer interconversion in three different media, namely, in the gas phase, in a solvent continuum, and in a microhydrated environment where the first solvation layer is described explicitly by one or two water molecule. In all cases, the transition state has been localized and identified. Proton affinities, deprotonation energies and the Raman spectra are reported analyzed and discussed. RESULTS: The 1 tautomer of cyanoform is shown to be more stable than 2 form by only 1.8 and 14.1 kcal/mol in the gas phase using B3LYP/6-311 ++G** and MP2/6-311 ++G** level of theory, respectively. This energy difference is reduced to 0.7 and 13.4 kcal/mol in water as a solvent using CPCM model using B3LYP/6-311 ++G** and MP2/6-311 ++G** level of theory, respectively. The potential energy barrier for this proton transfer process in the gas phase is 77.5 kcal/mol at MP2/6-311 ++G** level of theory. NBO analysis, analysis of the electrostatic potential (ESP) of the charge distribution, donor–acceptor interactions and charge transfer interactions in 1 and 2 are performed and discussed. CONCLUSIONS: Gross solvent continuum effects have but negligible effect on this barrier. Inclusion of one and two water molecules to describe explicitly the first solvation layer, within the supermolecule model, lowers the barrier considerably (29.0 and 7.6 kcal/mol, respectively). Natural bond orbital (NBO) analysis indicated that the stability of the cyanoform arising from charge delocalization. A very good agreement between experimental and theoretical data has been found at MP2/6-311 ++G** for the energies. On other hand, B3LYP/6-311 ++G** level of theory has good agreement with experimental spectra for CF compound. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13065-016-0166-z) contains supplementary material, which is available to authorized users.
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spelling pubmed-48287672016-04-13 Tautomerization, acidity, basicity, and stability of cyanoform: a computational study Elroby, Shaaban A. Chem Cent J Research Article BACKGROUND: Cyanoform is long known as one of the strongest acid. Cyanoform is only stable below −40 °C. The issue of the stability and tautomeric equilibria of cyanoform (CF) are investigated at the DFT and MP2 levels of theory. The present work presents a detailed study of structural tautomer interconversion in three different media, namely, in the gas phase, in a solvent continuum, and in a microhydrated environment where the first solvation layer is described explicitly by one or two water molecule. In all cases, the transition state has been localized and identified. Proton affinities, deprotonation energies and the Raman spectra are reported analyzed and discussed. RESULTS: The 1 tautomer of cyanoform is shown to be more stable than 2 form by only 1.8 and 14.1 kcal/mol in the gas phase using B3LYP/6-311 ++G** and MP2/6-311 ++G** level of theory, respectively. This energy difference is reduced to 0.7 and 13.4 kcal/mol in water as a solvent using CPCM model using B3LYP/6-311 ++G** and MP2/6-311 ++G** level of theory, respectively. The potential energy barrier for this proton transfer process in the gas phase is 77.5 kcal/mol at MP2/6-311 ++G** level of theory. NBO analysis, analysis of the electrostatic potential (ESP) of the charge distribution, donor–acceptor interactions and charge transfer interactions in 1 and 2 are performed and discussed. CONCLUSIONS: Gross solvent continuum effects have but negligible effect on this barrier. Inclusion of one and two water molecules to describe explicitly the first solvation layer, within the supermolecule model, lowers the barrier considerably (29.0 and 7.6 kcal/mol, respectively). Natural bond orbital (NBO) analysis indicated that the stability of the cyanoform arising from charge delocalization. A very good agreement between experimental and theoretical data has been found at MP2/6-311 ++G** for the energies. On other hand, B3LYP/6-311 ++G** level of theory has good agreement with experimental spectra for CF compound. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13065-016-0166-z) contains supplementary material, which is available to authorized users. Springer International Publishing 2016-04-11 /pmc/articles/PMC4828767/ /pubmed/27073411 http://dx.doi.org/10.1186/s13065-016-0166-z Text en © Elroby. 2016 Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
spellingShingle Research Article
Elroby, Shaaban A.
Tautomerization, acidity, basicity, and stability of cyanoform: a computational study
title Tautomerization, acidity, basicity, and stability of cyanoform: a computational study
title_full Tautomerization, acidity, basicity, and stability of cyanoform: a computational study
title_fullStr Tautomerization, acidity, basicity, and stability of cyanoform: a computational study
title_full_unstemmed Tautomerization, acidity, basicity, and stability of cyanoform: a computational study
title_short Tautomerization, acidity, basicity, and stability of cyanoform: a computational study
title_sort tautomerization, acidity, basicity, and stability of cyanoform: a computational study
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4828767/
https://www.ncbi.nlm.nih.gov/pubmed/27073411
http://dx.doi.org/10.1186/s13065-016-0166-z
work_keys_str_mv AT elrobyshaabana tautomerizationaciditybasicityandstabilityofcyanoformacomputationalstudy