Citation

Morgado P, Garcia AR, Ilharco LM, Marcos J, Anastácio M, Martins LF, Filipe EJ. J. Phys. Chem. B 2016; ePub(ePub): ePub.

Copyright

(Copyright © 2016, American Chemical Society)

DOI

10.1021/acs.jpcb.6b04297

PMID

27574862

Abstract

The paper reports a combined thermodynamic, spectroscopic and computational study, on the interactions and structure of binary mixtures of hydrogenated and fluorinated substances that simultaneously interact through strong hydrogen bonding. Four binary mixtures of hydrogenated and fluorinated alcohols have been studied, namely (ethanol + 2,2,2- trifluoroethanol), (ethanol + 2,2,3,3,4,4,4-heptafluoro-1-butanol), (1-butanol + 2,2,2-trifluoroethanol), and (1-butanol + 2,2,3,3,4,4,4-heptafluoro-1-butanol). Excess molar volumes and vibrational spectra of all four binary mixtures have been measured as a function of composition at 298K, and molecular dynamics simulations have been performed. The systems display a complex behavior when compared with mixtures of hydrogenated alcohols and mixtures of alkanes and perfluoroalkanes. The combined analysis of the results from the different approaches indicates that this results from a balance between preferential hydrogen bonding between the hydrogenated and fluorinated alcohols and the unfavorable dispersion forces between the hydrogenated and fluorinated chains. As chain length increases, the contribution of dispersion increases and overcomes the contribution of H-bonds. In terms of the liquid structure, the simulations suggest the possibility of segregation between the hydrogenated and fluorinated segments, a hypothesis corroborated by the spectroscopic results. Furthermore, a quantitative analysis of the infrared spectra reveals that the presence of fluorinated groups induces conformational changes in the hydrogenated chains from the usually preferred all-trans to more globular arrangements involving gauche conformations. Conformational rearrangements at the CCOH dihedral angle upon mixing are also disclosed by the spectra.

Language: en