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(4+2) and (2+2) Cycloadditions of Benzyne to C60 and Zig-Zag Single-Walled Carbon Nanotubes: The Effect of the Curvature

Addition of benzyne to carbon nanostructures can proceed via (4+2) (1,4-addition) or (2+2) (1,2-addition) cycloadditions depending on the species under consideration. In this work, we analyze by means of density functional theory calculations the reaction mechanisms for the (4+2) and (2+2) cycloadditions of benzyne to nanostructures of different curvature, namely, C60 and a series of zig-zag single-walled carbon nanotubes. Our DFT calculations reveal that, except for the concerted (4+2) cycloaddition of benzyne to zig-zag single-walled carbon nanotubes, all cycloadditions studied are stepwise processes with the initial formation of a biradical singly-bonded intermediate. From this intermediate, the rotation of the benzyne moiety determines the course of the reaction. The Gibbs energy profiles lead to the following conclusions: (i) except for the 1,4-addition of benzyne to a six-membered ring of C60, all 1,2- and 1,4-additions studied are exothermic processes; (ii) for C60, the (2+2) benzyne cycloaddition is the most favoured reaction pathway; (iii) for zig-zag single-walled carbon nanotubes, the (4+2) benzyne cycloaddition is preferred over the (2+2) reaction pathway; and (iv) there is a gradual decrease in the exothermicity of the reaction and an increase of energy barriers as the diameter of the nanostructure of carbon is increased. By making use of the activation strain model, it is found that the deformation of the initial reactants in the rate-determining transition state is the key factor determining the chemoselectivity of the cycloadditions with benzyne

The following organizations are thanked for financial support: the Spanish government (MINECO, projects number CTQ2014-54306-P, CTQ2014-59212-P, and CTQ2013-48252-P), the Generalitat de Catalunya (project number 2014SGR931, Xarxa de Referència en Química Teòrica i Computacional, and ICREA Academia 2014 prize to M. S.), and the FEDER fund (European Fund for Regional Development) for the grant UNGI10-4E-801

© Journal of Physical Chemistry C, 2016, vol. 120, núm. 3, p. 1716-1726

American Chemical Society (ACS)

Manager: Ministerio de Economía y Competitividad (Espanya)
Generalitat de Catalunya. Agència de Gestió d’Ajuts Universitaris i de Recerca
Author: Martínez López, Juan Pablo
Langa, Fernando
Bickelhaupt, F. Matthias
Osuna Oliveras, Sílvia
Solà i Puig, Miquel
Date: 2016
Abstract: Addition of benzyne to carbon nanostructures can proceed via (4+2) (1,4-addition) or (2+2) (1,2-addition) cycloadditions depending on the species under consideration. In this work, we analyze by means of density functional theory calculations the reaction mechanisms for the (4+2) and (2+2) cycloadditions of benzyne to nanostructures of different curvature, namely, C60 and a series of zig-zag single-walled carbon nanotubes. Our DFT calculations reveal that, except for the concerted (4+2) cycloaddition of benzyne to zig-zag single-walled carbon nanotubes, all cycloadditions studied are stepwise processes with the initial formation of a biradical singly-bonded intermediate. From this intermediate, the rotation of the benzyne moiety determines the course of the reaction. The Gibbs energy profiles lead to the following conclusions: (i) except for the 1,4-addition of benzyne to a six-membered ring of C60, all 1,2- and 1,4-additions studied are exothermic processes; (ii) for C60, the (2+2) benzyne cycloaddition is the most favoured reaction pathway; (iii) for zig-zag single-walled carbon nanotubes, the (4+2) benzyne cycloaddition is preferred over the (2+2) reaction pathway; and (iv) there is a gradual decrease in the exothermicity of the reaction and an increase of energy barriers as the diameter of the nanostructure of carbon is increased. By making use of the activation strain model, it is found that the deformation of the initial reactants in the rate-determining transition state is the key factor determining the chemoselectivity of the cycloadditions with benzyne
The following organizations are thanked for financial support: the Spanish government (MINECO, projects number CTQ2014-54306-P, CTQ2014-59212-P, and CTQ2013-48252-P), the Generalitat de Catalunya (project number 2014SGR931, Xarxa de Referència en Química Teòrica i Computacional, and ICREA Academia 2014 prize to M. S.), and the FEDER fund (European Fund for Regional Development) for the grant UNGI10-4E-801
Format: application/pdf
Citation: 024717
ISSN: 1932-7447 (versió paper)
1932-7455 (versió electrònica)
Document access: http://hdl.handle.net/10256/12192
Language: eng
Publisher: American Chemical Society (ACS)
Collection: MINECO/PE 2015-2017/CTQ2014-54306-P
MINECO/PE 2015-2017/CTQ2014-59212-P
AGAUR/2014-2016/2014 SGR-931
Versió postprint del document publicat a: http://dx.doi.org/10.1021/acs.jpcc.5b11499
Articles publicats (D-Q)
info:eu-repo/grantAgreement/EC/FP7/630978
Is part of: © Journal of Physical Chemistry C, 2016, vol. 120, núm. 3, p. 1716-1726
Rights: Tots els drets reservats
Subject: Ciclització (Química)
Ring formation (Chemistry)
Title: (4+2) and (2+2) Cycloadditions of Benzyne to C60 and Zig-Zag Single-Walled Carbon Nanotubes: The Effect of the Curvature
Type: info:eu-repo/semantics/article
Repository: DUGiDocs

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