PREPARATION AND CHARACTERIZATION OF ALIPHATIC DIPHENYL ESTERS INTENDED AS PRECURSORS FOR POLYESTERS

An extensive number of aliphatic diphenyl esters, C6H5OOC(CH2)nCOOC6H5 (n = O,...,8,10,11,12,14), have been prepared in pure form. The crystalline melting points these esters exhibit an odd-even temperature behaviour, with the higher-melting even series (n even) displaying a minimum for n = 8 while the odd series shows an almost monotonic slow increase. High-resolution C-13 nuclear magnetic resonance (n.m.r.) spectroscopy of the esters in CDCl3 and C6D6 allows all non-symmetrical carbons to be resolved, even the seven different methylenes for n = 14. This unusual spectral sensitivity is primarily based on similar data from phenyl esters, interpreted as the results of an apparent macrocyclic conformation of the larger diphenyl esters. High-performance size exclusion chromatography (s.e.c.) of diphenyl esters, phenyl esters, aromatic and linear hydrocarbons in tetrahydrofuran, toluene and chloroform points to specific phenyl ester-solvent interactions, which obscure a potential s.e.c. conformational analysis of the diphenyl esters.