title: Electronic [UV-Visible] and vibrational [FT-IR, FT-Raman] investigation and NMR-mass spectroscopic analysis of terephthalic acid using quantum Gaussian calculations.
abstract: In this research work, the vibrational IR, polarization Raman, NMR and mass spectra of terephthalic acid (TA) were recorded. The observed fundamental peaks (IR, Raman) were assigned according to their distinctiveness region. The hybrid computational calculations were carried out for calculating geometrical and vibrational parameters by DFT (B3LYP and B3PW91) methods with 6-31++G(d,p) and 6-311++G(d,p) basis sets and the corresponding results were tabulated. The molecular mass spectral data related to base molecule and substitutional group of the compound was analyzed. The modification of the chemical property by the reaction mechanism of the injection of dicarboxylic group in the base molecule was investigated. The (13)C and (1)H NMR spectra were simulated by using the gauge independent atomic orbital (GIAO) method and the absolute chemical shifts related to TMS were compared with experimental spectra. The study on the electronic and optical properties; absorption wavelengths, excitation energy, dipole moment and frontier molecular orbital energies, were performed by hybrid Gaussian calculation methods. The orbital energies of different levels of HOMO and LUMO were calculated and the molecular orbital lobe overlapping showed the inter charge transformation between the base molecule and ligand group. From the frontier molecular orbitals (FMO), the possibility of electrophilic and nucleophilic hit also analyzed. The NLO activity of the title compound related to Polarizability and hyperpolarizability were also discussed. The present molecule was fragmented with respect to atomic mass and the mass variation depends on the substitutions have also been studied.
authors.affiliation: Department of Physics, Indra Ganesan College of Engineering, Tiruchirappalli, Tamilnadu, India.
authors.forename: N
authors.initials: N
authors.lastname: Karthikeyan
authors.affiliation: Department of Physics, Anna University, BIT Campus, Tiruchirappalli, Tamilnadu, India.
authors.forename: J Joseph
authors.initials: JJ
authors.lastname: Prince
authors.affiliation: Department of Physics, A.V.C. College, Mayiladuthurai, Tamilnadu, India. Electronic address: ramalingam.physics@gmail.com.
authors.forename: S
authors.initials: S
authors.lastname: Ramalingam
authors.affiliation: Department of Physics, Tagore Arts College, Puducherry, India.
authors.forename: S
authors.initials: S
authors.lastname: Periandy
mesh_terms: D066241:Carbon-13 Magnetic Resonance Spectroscopy; D004583:Electrons; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008958:Models, Molecular; D008968:Molecular Conformation; D016011:Normal Distribution; D010795:Phthalic Acids / Q000737:chemistry*; D066244:Proton Magnetic Resonance Spectroscopy; D011789:Quantum Theory; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D055672:Static Electricity; D013816:Thermodynamics; D014732:Vibration
chemical_list: D010795:Phthalic Acids; C011363:terephthalic acid
keywords: Dicarboxylic group; FMO; Hybrid Gaussian; NLO activity; Optical properties; Terephthalic acid