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Molecules 2017, 22(4), 593; doi:10.3390/molecules22040593

A Study about Regioisomeric Hydroquinones with Multiple Intramolecular Hydrogen Bonding

1
Programa Institucional de Fomento a la Investigación, Desarrollo e Innovación, Universidad Tecnológica Metropolitana, Ignacio Valdivieso 2409, Casilla 9845, Santiago 8940577, Chile
2
Departamento de Ciencias Químicas, Facultad de Ciencias Exactas, Universidad Andrés Bello, Autopista Concepción-Talcahuano 7100, Talcahuano 4300866, Chile
3
Departamento de Química Orgánica y Fisicoquímica, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santos Dumont 964, Casilla 233, Santiago 8380494, Chile
4
Departamento de Química, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Casilla 653, Santiago 7800003, Chile
5
Instituto de Química de Recursos Naturales, Universidad de Talca, Av. Lircay s/n, Casilla 747, Talca 3460000, Chile
*
Authors to whom correspondence should be addressed.
Academic Editor: Steve Scheiner
Received: 20 February 2017 / Revised: 27 March 2017 / Accepted: 4 April 2017 / Published: 7 April 2017
(This article belongs to the Special Issue Intramolecular Hydrogen Bonding 2017)
View Full-Text   |   Download PDF [7474 KB, uploaded 7 April 2017]   |  

Abstract

A theoretical exploration about hydrogen bonding in a series of synthetic regioisomeric antitumor tricyclic hydroquinones is presented. The stabilization energy for the intramolecular hydrogen bond (IHB) formation in four structurally different situations were evaluated: (a) IHB between the proton of a phenolic hydroxyl group and an ortho-carbonyl group (forming a six-membered ring); (b) between the oxygen atom of a phenolic hydroxyl group and the proton of an hydroxyalkyl group (seven membered ring); (c) between the proton of a phenolic hydroxyl group with the oxygen atom of the hydroxyl group of a hydroxyalkyl moiety (seven-membered ring); and (d) between the proton of a phenolic hydroxyl group and an oxygen atom directly bonded to the aromatic ring in ortho position (five-membered ring). A conformational analysis for the rotation around the hydroxyalkyl substituent is also performed. It is observed that there is a correspondence between the conformational energies and the IHB. The strongest intramolecular hydrogen bonds are those involving a phenolic proton and a carbonyl oxygen atom, forming a six-membered ring, and the weakest are those involving a phenolic proton with the oxygen atom of the chromenone, forming five-membered rings. Additionally, the synthesis and structural assignment of two pairs of regioisomeric hydroquinones, by 2D-NMR experiments, are reported. These results can be useful in the design of biologically-active molecules. View Full-Text
Keywords: hydroquinone; hydrogen bond; DFT; NBO; AIM hydroquinone; hydrogen bond; DFT; NBO; AIM
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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).

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Martínez-Cifuentes, M.; Cardona, W.; Saitz, C.; Weiss-López, B.; Araya-Maturana, R. A Study about Regioisomeric Hydroquinones with Multiple Intramolecular Hydrogen Bonding. Molecules 2017, 22, 593.

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