Indian Journal of Pure & Applied Physics Vol. 51, February 2013, pp. 104-111 Study of molecular interaction between some primary alcohols and anilines using concentration dependent dielectric properties A N Prajapati 1 , V A Rana 2 * & A D Vyas 2 1 Department of Applied Physics, Faculty of Technology and Engineering, M S University of Baroda, Vadodara, India 2 Department of Physics, School of Sciences, Gujarat University, Ahmedabad, India *E-mail: ranava2001@yahoo.com, anprajapati2006@yahoo.co.in Received 13 January 2012; revised 3 September 2012; accepted 19 October 2012 The static dielectric constant ( 0 ) and optical dielectric constant ( ∞ = n 2 ) of binary mixtures of some lower order primary alcohols with aniline, 2-fluoroaniline and 4-fluoroaniline over the concentration range (0.0, 0.1, …. 1.0) by volume fractions are measured at fix frequency 2 MHz using precision LCR meter and Abbe’s refractometer, respectively. The excess dielectric constant, Kirkwood correlation parameter and Bruggeman parameter have been evaluated. The variations of these parameters with composition indicate the presence of molecular interaction between the participating components in these mixtures. Keywords: Bruggeman parameter, Excess static dielectric constant, Fluoro substituted anilines, Hydrogen bonding, Molecular ineraction 1 Introduction The relation between chemical structure, and the static and relaxation properties of liquids presents a fascinating puzzle to the physical chemists 1 . Dielectric studies about binary mixtures are important to understand the intermolecular interactions in the mixture due to the dipole-dipole interactions and hydrogen-bonding 2 . Such studies enable one to give the explicit information on molecular dynamics of liquids and their mixtures. Among the researchers, alcohols are the center of interest. Because of its outstanding role in applied sciences, hydrogen bonding in liquid systems has been intensively studied for long and it is still subject to a lively scientific debate. As molecules with –OH groups form associative liquid due to hydrogen bonding, the effect of the presence of molecules with other groups on hydrogen bonded molecules is very important to understand the behaviour of hydrogen bonding. Martinez Jimenez et al 3 . have studied the dielectric behaviour and molecular polarization process in the mixtures of some alcohols with n-alkane using TDR technique in the frequency range dc to 5 GHz. Chaudhari et al 4 . have studied the dielectric properties of butyl acetate-alcohol mixtures using TDR technique. Sengwa et al 5 . reported the dielectric behaviour and hydrogen bond molecular interaction study of formamide with mono-, di-and tri-hydric alcohols. Mohan et al 6 . have reported dielectric and conformational studies of 1-PrOH with alkyl benzoates at different temperatures in the radio, microwave and optical frequency regions. Aniline is potentially important aromatic amine, used in the manufacture of rubber-processing chemicals, explosives, plastics, anti-oxidants and varnishes. Fluoro substituted anilines are used as an intermediate for the preparation of pharmaceutical, pesticide and dyes. Rana et al 7 . carried out dielectric relaxation study of mixtures of 1-propanol with some chloro substituted and flouro substituted anilines at different temperatures using TDR technique in the frequency range from 10 MHz to 20 GHz. A good number of literature survey shows that though attempts have already been made to study binary mixtures of alcohols with aniline and substituted anilines, but systematic studies with concentration dependences are still scarce in case of fluoro substituted anilines 1-15 (2-FA, 4-FA) with alcohols (MeOH, 1-PrOH and 1-BuOH). These facts have prompted us to study dielectric properties of the binary mixtures of alcohols (MeOH, 1-PrOH and 1-BuOH) as one component with aniline (AN) and fluoro substituted anilines (2-FA, 4-FA) as the other component in pure liquid state over entire concentration range. In the present work, static dielectric constant (ε 0 ) and optical dielectric constant (ε  ), excess dielectric constant (ε 0 ) E , Kirkwood correlation factors (g eff , g f ) and Bruggeman parameter (f B ) of the aniline (AN) and