Direction of the dipole moment in the ester group

The directions of the dipole moments in esters RCOOR′ in which R and R′ are alkyl or aryl groups have been deduced by analysis of experimental values of dipole moments of six compounds containing two polar groups, one or both of which are esters. New determinations of molecular dipole moments are reported for dimethyl trans-1,4-cyclohexanedicarboxylate and for trans-1,4-cyclohexanediol diacetate. The moment of the ester group is directed (in the positive sense) at an angle τE = 123 ± 3° from the R-CO axis in both aromatic and aliphatic esters, formates excepted. © 1981 American Chemical Society.