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Exploring the validity of the Glidewell–Lloyd extension of Clar’s π-sextet rule: assessment from polycyclic conjugated hydrocarbons

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Abstract

The Clar π-sextet rule was formulated as a tool to qualitatively assign the local aromatic character of six-membered rings in benzenoid species. This simple rule has been widely validated both experimentally and theoretically. In 1984, Glidewell and Lloyd reported an extension of this rule to polycyclic conjugated hydrocarbons having rings with any even number of carbon atoms in their structure. In this work, we assess the validity of the Glidewell–Lloyd extension in 69 polycyclic conjugated hydrocarbons composed of different combinations of four-, six-, and eight-membered rings. Our results support the validity of this extension with some exceptions that are discussed. Finally, a minor modification to the rule is proposed.

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Acknowledgments

This work has been supported by the Ministerio de Economía y Competitividad (MINECO) of Spain (Project CTQ2014-54306-P) and the Generalitat de Catalunya (Project 2014SGR931, Xarxa de Referència en Química Teòrica i Computacional, ICREA Academia 2014 prize for M.S., and Grant No. 2014FI_B 00429 to O.E.B.). The EU under the FEDER Grant UNGI10-4E-801 (European Fund for Regional Development) has also funded this research.

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Authors and Affiliations

  1. Institut de Química Computacional i Catàlisi (IQCC) and Departament de Química, Universitat de Girona, Campus Montilivi, 17003, Girona, Spain

    Ouissam El Bakouri, Ferran Feixas & Miquel Solà

  2. Departament de Química Inorgànica i Orgànica and Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, Martí i Franquès 1-11, 08028, Barcelona, Catalonia, Spain

    Jordi Poater

  3. Institució Catalana de Recerca i Estudis Avançats (ICREA), Pg. Lluís Companys 23, 08010, Barcelona, Catalonia, Spain

    Jordi Poater

Authors
  1. Ouissam El Bakouri
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  2. Jordi Poater
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  3. Ferran Feixas
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  4. Miquel Solà
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Correspondence to Miquel Solà.

Additional information

This work is dedicated to Prof. Dr. Alberto Vela as a proof of our admiration for his brilliant contributions to chemistry.

Published as part of the special collection of articles “Festschrift in honour of A. Vela”.

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El Bakouri, O., Poater, J., Feixas, F. et al. Exploring the validity of the Glidewell–Lloyd extension of Clar’s π-sextet rule: assessment from polycyclic conjugated hydrocarbons. Theor Chem Acc 135, 205 (2016). https://doi.org/10.1007/s00214-016-1970-1

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