Conformational Characteristics of Aliphatic Diesters Derived from Fluorinated Diacids

Abstract

A comparative study of the polarity and conformational characteristics of diethyl hexafluoroglutarate (DEFG) and its hydrogenated diester counterpart, diethyl glutarate (DEG), is reported. The value at 30 °C of the mean-square dipole moment 〈μ2〉 of the latter compound, 5.26 D2, is nearly 2 times larger the value of this quantity for the fluorinated diester, which amounts to 12.1 D2 at the same temperature. Values of the conformational energies associated with the rotational states about the skeletal bonds of the acid residue were calculated by combining molecular mechanics with the critical interpretation of the mean-square dipole moment of these compounds, finding that the rotational populations about the different skeletal bonds are similar in both molecules. The evaluation of 〈μ2〉 as a function of the conformational energies indicates that the experimental results are reproduced assuming that the conformation in which the C*O* group eclipses the Cα−Cβ bond in the CβCαC*(O*)O residue is less stable than...