Jacobs Journal of Organic Chemistry

The Mechanism, Kinetic Study and Non-Linear Optical Properties (NLO) of Para-Chloroaniline Using DFT Approach

*H.M. Mustafa
Department Of Chemistry, Cairo University, Egypt, Egypt

*Corresponding Author:
H.M. Mustafa
Department Of Chemistry, Cairo University, Egypt, Egypt
Email:Mali2007@hotmail.com

Published on: 2019-02-25

Abstract

The synthesis of poly-p-chloroaniline (PpCA) by oxidative chemical polymerization using potassium dichromate as oxidizing agent was carried out. The optimum conditions for the polymerization reaction and the order of reactions and thermodynamic activation parameters were investigated. A molecular mechanism for the oxidation of p-chloroaniline using potassium dichromate is proposed. The TGA analysis and spectroscopic studies IR, UV–vis and elemental analysis have evidenced the structure of polymeric chain. The surface morphology of the obtained polymer was characterized by X-ray diffraction and transmission electron microscopy (TEM). Moreover, determinations of dielectric properties of the prepared polymer were carried out. The a.c conductivity (σac) of (PpCA) was investigated as a function of frequency and temperature. The microscopic conduction mechanism of charge carries over the potential barrier in polymer backbone was found classical hopping model. The electronic structure of neutral PpCA, radical cation and dimmer radical cation are investigated theoretically at the B3LYP/6-311G**level of theory. The mechanism of the polymerization process are discussed and analyzed. The calculated EHOMO and ELUMO energies of the studied compounds can be used to calculate the global properties; chemical hardness (η), softness (S) and electronegativity (χ). The calculated nonlinear optical parameters (NLO); polarizibilty (α), anisotropy of the polarizibility (?α) and first order hyperpolarizibility (β) of the studied compounds show promising optical properties. 3D-plots of the molecular electrostatic potential (MEP) for neutral monomer and radical cation dimer are investigated and analyzed showing the distribution of electronic density of orbitals describing the electrophilic and nucleophilic sites of the neutral monomer and radical cation dimer.

Keywords

Oxidative chemical polymerization; p-chloroaniline characterization; Kinetics; Electrical conductivity; DFT calculations; NLO properties

Introduction

Conducting polymers have been extensively studied due to their interesting electrical and electrochemical properties (Road, 2000). Polyaniline (PANI) is one of the most studied conducting polymers due to its simple synthesis method[1]. It has various potential applications in many high performance devices [2-8]. A common feature of conducting polymer is conjugation of ????-electrons extending over the length of the polymer backbone [9]. Polymerization of conducting polymer may be performed by chemical [10] or electrochemical [11] methods. Kinetics of the oxidation of p-chloroaniline, m-chloroaniline and p-chloroaniline using Fe (III) as oxidant and 1,10 -phenanthroline as catalyst were investigated spectrophotometrically [12], The reaction obeys first order kinetics both in the substrate and iron (III). Plots of 1/k1 versus 1/ [catalyst] 2, 1/K1 [H+] versus [H+] 2 and 1/k1 versus [HSO-4]2 are linear with positive intercepts on the 1/k1 axis in each case. The stability constant of the complex formed between Fe (III) and catalyst and the activation parameters have been evaluated. A suitable mechanism has been proposed. Three principal ways to synthesize the polychloroanilines such as chemically oxidative solution polymerization, chemically oxidative emulsion polymerization and electrochemical polymerization are concluded. The resulted polychloroanilines possess-conjugated structures like polyaniline backbones. And the presence of chloro-substituted groups accounts for excellent solubility and sensitive electrocatalysis. The polychloroanilines are of stronger catalysis sensitivity and higher stability in modified electrode than inorganic compounds and other conducting polymers. They are new functional materials with great development potential. They can be applied in a wide area such as modified electrode, pH sensor and gas separation membrane [13]. To understand the orientation effect of polychloroaniline on the electrophilic substitution, the charges of carbon atoms in the benzene ring and the energy of σ complexes formed in the electrophilic substitution were computed by B3LYP at 6-311G** level, according to density functional theory (DFT). Results showed that ortho-and para-chlorines were preferentially substituted instead of meta-chlorines, because the charges of ortho-and para-carbon atoms, the energy of ortho-and para-σ complexes were less than that of meta [14].