Solvent Effects on the Monomer/Hydrogen-Bonded Dimer Equilibrium in Carboxylic Acids: (+)-(S)-Ketopinic Acid as a Case Study

The hydrogen‐bond‐assisted self‐association process of a chiral semirigid carboxylic acid, namely, (+)‐(S)‐ketopinic acid, has been studied. The multiconformational monomer/dimer equilibrium has been evaluated by means of a concentration‐dependent FTIR study that enabled the experimental equilibrium...

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Bibliographic Details
Published in:	Chemistry, an Asian journal Vol. 11; no. 12; pp. 1798 - 1803
Main Authors:	RodriguezOrtega, Pilar Gema, MontejoGamez, Manuel, MarquezLopez, Fernando, LopezGonzalez, Juan Jesús
Format:	Journal Article
Language:	English
Published:	Germany Blackwell Publishing Ltd 21-06-2016 Wiley Subscription Services, Inc
Subjects:	Acids carboxylic acids Chemistry crystal growth density functional calculations Equilibrium hydrogen bonding self-association self-association density functional calculations hydrogen bonding crystal growth carboxylic acids
Online Access:	Get full text
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Summary:	The hydrogen‐bond‐assisted self‐association process of a chiral semirigid carboxylic acid, namely, (+)‐(S)‐ketopinic acid, has been studied. The multiconformational monomer/dimer equilibrium has been evaluated by means of a concentration‐dependent FTIR study that enabled the experimental equilibrium constants of the dimer formation reaction (Kdim) to be determined in two solvents of different polarity. In CDCl3, dimeric forms predominate, even in diluted solutions (KdimCF =5.074), whereas in CD3CN the self‐association process is hindered and monomers are always the main species, irrespective of solute concentration (KdimAN =0.194). The reliability of the dimerization constants and the derived mono‐ and dimeric experimental fractions have been proven by means of accurate matching between the experimental vibrational circular dichroism spectra of the species and the theoretical spectra generated by considering the simultaneous weighted contributions of the concomitant monomers and dimers. Structures of states: The experimental determination of dimerization constants of (+)‐(S)‐ketopinic acid and subsequent estimation of the fraction of concomitant mono‐ and dimeric forms as a function of concentration allow the vibrational circular dichroism spectra of the species in chloroform and acetonitrile to be reproduced theoretically (see figure).
Bibliography:	ArticleID:ASIA201600199 ark:/67375/WNG-X9F4W4TH-C istex:D3A11D81DF86EB9F46DACB5B2B7B32DFCAEBBFA1 University of Jaén - No. UJA2014/06/36 Fundación Ramón Areces ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	1861-4728 1861-471X
DOI:	10.1002/asia.201600199