Dielectric studies of hydrogen bonded polar binary mixtures of ethyl benzoate with aromatic amines

The chosen liquids: ethyl benzoate, aniline and n-methyl aniline are high boiling point liquids for possible microwave applications. Dielectric measurements are carried out at 300 KHz, 5.59 GHz, 7.95 GHz, 33.7 GHz, 72 GHz and at optical frequency on the above polar liquids and their equimolar binary mixtures diluted in non-polar solvent (benzene). Cole-Davidson plot is obtained for the binary mixture of ethyl benzoate and aniline whereas Debye plot is observed for the binary mixture of ethyl benzoate and N-methyl aniline in dilute solutions of benzene. The binary mixture of an associated liquid aniline and non-associated liquid ethyl benzoate leads to formation of an extensive tree like hydrogen bonded system. In N-methyl aniline, where one hydrogen atom of the -NH2 group is replaced by a methyl group, it acts as a terminator to prevent hydrogen bonding. The experimentally determined dipole moments are compared with computational results obtained from semiempirical molecular orbital package MOPAC Version 6.0 and ab initio calculations using the Gaussian 92W program. The results are discussed.