Cargando…

Urethane Formation with an Excess of Isocyanate or Alcohol: Experimental and Ab Initio Study

A kinetic and mechanistic investigation of the alcoholysis of phenyl isocyanate using 1-propanol as the alcohol was undertaken. A molecular mechanism of urethane formation in both alcohol and isocyanate excess is explored using a combination of an accurate fourth generation Gaussian thermochemistry...

Descripción completa

Detalles Bibliográficos
Autores principales: Cheikh, Wafaa, Rózsa, Zsófia Borbála, Camacho López, Christian Orlando, Mizsey, Péter, Viskolcz, Béla, Szőri, Milán, Fejes, Zsolt
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2019
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6835639/
https://www.ncbi.nlm.nih.gov/pubmed/31546721
http://dx.doi.org/10.3390/polym11101543
_version_ 1783466720037437440
author Cheikh, Wafaa
Rózsa, Zsófia Borbála
Camacho López, Christian Orlando
Mizsey, Péter
Viskolcz, Béla
Szőri, Milán
Fejes, Zsolt
author_facet Cheikh, Wafaa
Rózsa, Zsófia Borbála
Camacho López, Christian Orlando
Mizsey, Péter
Viskolcz, Béla
Szőri, Milán
Fejes, Zsolt
author_sort Cheikh, Wafaa
collection PubMed
description A kinetic and mechanistic investigation of the alcoholysis of phenyl isocyanate using 1-propanol as the alcohol was undertaken. A molecular mechanism of urethane formation in both alcohol and isocyanate excess is explored using a combination of an accurate fourth generation Gaussian thermochemistry (G4MP2) with the Solvent Model Density (SMD) implicit solvent model. These mechanisms were analyzed from an energetic point of view. According to the newly proposed two-step mechanism for isocyanate excess, allophanate is an intermediate towards urethane formation via six-centered transition state (TS) with a reaction barrier of 62.6 kJ/mol in the THF model. In the next step, synchronous 1,3-H shift between the nitrogens of allophanate and the cleavage of the C–N bond resulted in the release of the isocyanate and the formation of a urethane bond via a low-lying TS with 49.0 kJ/mol energy relative to the reactants. Arrhenius activation energies of the stoichiometric, alcohol excess and the isocyanate excess reactions were experimentally determined by means of HPLC technique. The activation energies for both the alcohol (measured in our recent work) and the isocyanate excess reactions were lower compared to that of the stoichiometric ratio, in agreement with the theoretical calculations.
format Online
Article
Text
id pubmed-6835639
institution National Center for Biotechnology Information
language English
publishDate 2019
publisher MDPI
record_format MEDLINE/PubMed
spelling pubmed-68356392019-11-25 Urethane Formation with an Excess of Isocyanate or Alcohol: Experimental and Ab Initio Study Cheikh, Wafaa Rózsa, Zsófia Borbála Camacho López, Christian Orlando Mizsey, Péter Viskolcz, Béla Szőri, Milán Fejes, Zsolt Polymers (Basel) Article A kinetic and mechanistic investigation of the alcoholysis of phenyl isocyanate using 1-propanol as the alcohol was undertaken. A molecular mechanism of urethane formation in both alcohol and isocyanate excess is explored using a combination of an accurate fourth generation Gaussian thermochemistry (G4MP2) with the Solvent Model Density (SMD) implicit solvent model. These mechanisms were analyzed from an energetic point of view. According to the newly proposed two-step mechanism for isocyanate excess, allophanate is an intermediate towards urethane formation via six-centered transition state (TS) with a reaction barrier of 62.6 kJ/mol in the THF model. In the next step, synchronous 1,3-H shift between the nitrogens of allophanate and the cleavage of the C–N bond resulted in the release of the isocyanate and the formation of a urethane bond via a low-lying TS with 49.0 kJ/mol energy relative to the reactants. Arrhenius activation energies of the stoichiometric, alcohol excess and the isocyanate excess reactions were experimentally determined by means of HPLC technique. The activation energies for both the alcohol (measured in our recent work) and the isocyanate excess reactions were lower compared to that of the stoichiometric ratio, in agreement with the theoretical calculations. MDPI 2019-09-22 /pmc/articles/PMC6835639/ /pubmed/31546721 http://dx.doi.org/10.3390/polym11101543 Text en © 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Cheikh, Wafaa
Rózsa, Zsófia Borbála
Camacho López, Christian Orlando
Mizsey, Péter
Viskolcz, Béla
Szőri, Milán
Fejes, Zsolt
Urethane Formation with an Excess of Isocyanate or Alcohol: Experimental and Ab Initio Study
title Urethane Formation with an Excess of Isocyanate or Alcohol: Experimental and Ab Initio Study
title_full Urethane Formation with an Excess of Isocyanate or Alcohol: Experimental and Ab Initio Study
title_fullStr Urethane Formation with an Excess of Isocyanate or Alcohol: Experimental and Ab Initio Study
title_full_unstemmed Urethane Formation with an Excess of Isocyanate or Alcohol: Experimental and Ab Initio Study
title_short Urethane Formation with an Excess of Isocyanate or Alcohol: Experimental and Ab Initio Study
title_sort urethane formation with an excess of isocyanate or alcohol: experimental and ab initio study
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6835639/
https://www.ncbi.nlm.nih.gov/pubmed/31546721
http://dx.doi.org/10.3390/polym11101543
work_keys_str_mv AT cheikhwafaa urethaneformationwithanexcessofisocyanateoralcoholexperimentalandabinitiostudy
AT rozsazsofiaborbala urethaneformationwithanexcessofisocyanateoralcoholexperimentalandabinitiostudy
AT camacholopezchristianorlando urethaneformationwithanexcessofisocyanateoralcoholexperimentalandabinitiostudy
AT mizseypeter urethaneformationwithanexcessofisocyanateoralcoholexperimentalandabinitiostudy
AT viskolczbela urethaneformationwithanexcessofisocyanateoralcoholexperimentalandabinitiostudy
AT szorimilan urethaneformationwithanexcessofisocyanateoralcoholexperimentalandabinitiostudy
AT fejeszsolt urethaneformationwithanexcessofisocyanateoralcoholexperimentalandabinitiostudy