Collect. Czech. Chem. Commun. 1981, 46, 1658-1674

Structure and molecular spectra of ethyl benzoate and diethyl terephthalate

Jan Štokra, Pavel Sedláčekb, Danica Doskočilováa, Bohdan Schneidera and Jan Lövya

a Institute of Macromolecular Chemistry, Czechoslovak Academy of Sciences, 162 06 Prague 6
b Chemopetrol, Silon, 391 11 Plana nad Luznici


Infrared and Raman spectra of ethyl benzoate and diethyl terephthalate were measured in their crystalline forms, in the glassy state and in the melt. With liquid samples, the NMR coupling constants 3JCH of the group -CO.O.CH2- were also measured. By analysis of these measurements it was found that in the liquid state of ethyl benzoate the following conformers are present: forms with a fully planar structure; forms with the methyl group twisted out of the aromatic and ester group plane by rotation about the O-C2H5 bond; and forms with non-planar mutual orientation of the ester group and the aromatic ring, formed by rotation about the Car-CO or CO-O bonds. The first two forms are also present in the crystalline modifications of ethyl benzoate. Diethyl terephthalate in the liquid state is present in forms analogous to those of ethyl benzoate; in addition, it contains isomers differing by the mutual orientation of the two ester groups on the aromatic ring.