The Influence of the Position of the Double Bond and Ring Size on the Stability of Hydrogen Bonded Complexes.

ABSTRACT: To study the influence of the position of the double bond and ring size on the stability of hydrogen bonded complexes, the 1:1 complexes formed between 2,2,2-trifluoroethanol (TFE) and three heterocyclic compounds including 2,3-dihydrofuran (2,3-DHF), 2,5-dihydrofuran (2,5-DHF) and 3,4-dihydropyran (3,4-DHP) were investigated systematically. The formation of hydrogen bonded TFE-2,3-DHF, TFE-2,5-DHF and TFE-3,4-DHP complexes were identified by gas phase FTIR spectroscopy at room temperature, and the OH-stretching fundamental transition of TFE was red shifted upon complexation. The competition between the O atom and ?-electrons bonding sites within the complexes was studied, and the O-H···? type hydrogen bond was found to be less stable than the O-H···O in all three cases. The observed red shifts of the OH-stretching fundamental transitions in the complexes were attributed to the formation of O-H···O hydrogen bond. Equilibrium constants of the complexation reactions were determined from measured and calculated OH-stretching fundamental intensities. Both theoretical calculations and experimental results reveal that the hydrogen bond strengths in the complexes follow the sequence: TFE-2,5-DHF?>?TFE-2,3-DHF???TFE-3,4-DHP, thus the position of the double bond exerts significantly larger influence than ring size on the stability of the selected hydrogen bonded complexes.

SUBMITTER: Cheng S 

PROVIDER: S-EPMC5596019 | biostudies-literature | 2017 Sep

REPOSITORIES: biostudies-literature