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4281360 
Journal Article 
Computational and experimental studies on dielectric relaxation and dipole moment of some anilines and phenol 
Maridevarmath, CV; Malimath, GH 
2017 
Yes 
Journal of Molecular Liquids
ISSN: 0167-7322 
Elsevier B.V. 
241 
845-851 
English 
WOS:000407535000102 
In the present study, the dielectric relaxation behaviour of four polar molecules namely 2-Nitroaniline, 4-Bromoaniline, 4-Chloroaniline and 4-Chlorophenol were studied in dilute solutions of benzene using microwave bench at 9.59 GHz frequency. The different parameters like, dielectric constant (epsilon'), dielectric loss (epsilon"), static dielectric constant (epsilon(0)) and optical permittivity (epsilon(infinity)) have been determined. Further from these values, dipole moment (mu) and relaxation time (T) were calculated for all the molecules following Gopalkrishna, microwave conductivity and the Higasi method. The dipole moment for all the molecules were also estimated theoretically from ab initio computations by using Density Functional Theory (DFT) calculations with the help of Gaussian 09W software. Dipole moments determined experimentally and through DFT computations are in good agreement with the dipole moments estimated by taking vector sum of group moments of Aniline, Nitrobenzene, Bromobenzene, Chlorobenzene and Phenol by neglecting interaction between pendant groups. The experimentally determined relaxation times were analyzed in terms of Stokes-Einstein-Debye (SED) theory and the results are compared with molecular radii estimated from DFT and Edward's atomic increment methods. Further, in order to understand the chemical stability and reactivity of all these molecules, highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO) and HOMO-LUMO energy gap were also estimated from DFT computations. Our experimental findings suggest that, 2-Nitroaniline exhibits simple Debye type relaxation behaviour while the other three samples exhibit Higasi's distribution of relaxation times which may be due to both overall and intra-molecular rotation of the molecules. Further, the HOMO-LUMO studies revealed that, 2-Nitroaniline is more chemically reactive having least energy gap and 4-Chlorophenol is least chemically reactive having highest energy gap among the four samples. (C) 2017 Elsevier B.V. All rights reserved. 
Dipole moment; Relaxation time; Gopalkrishna method; Higasi method; HOMO-LUMO