Vibrational Spectroscopic Investigation and Conformational Analysis of 1-Pentylamine: A Comparative Density Functional Study

Abstract

The possible stable conformers of 1-pentylamine (1-pa) molecule were experimentally and theoretically studied by FT-IR and Raman spectroscopy in the region of 4000-400 cm −1 . The optimized geometric structures concerning the minimum on the potential energy surface were investigated by Becke-3-Lee-Yang-Parr (B3LYP) density functional method together with 6-31G(d) basis set. Based on the energy calculations, 10 possible rotamers of 1-pa (TT, TG, GT, GT 1 , GG 1 , GG 2 , GG 3 , GG 4 , GG 5 and GG 6 ; T and G denote trans and gauge, respectively) were proposed. Optimized energies of the possible conformers were obtained in the gas phase and within the chloroform, carbon tetrachloride, methanol and water solvent environments all of which have different polarities. Comparison between the experimental and theoretical results based on the correlation graphics and mean absolute error calculations presented in this study indicates that density functional B3LYP method is able to provide satisfactory results for predicting vibrational wavenumbers and TT isomer is the most stable form of 1-pa molecule.

FT-IR, NMR spectroscopic and quantum mechanical investigations of two ferrocene derivatives

“…After the optimization, in order to confirm the convergence to minima on the potential surface and to evaluate the zero-point vibrational energies, harmonic vibrational frequencies of the present compounds were determined using analytic second derivatives with the 31G(d) method and then scaled by 0.955 (above 1800 cm -1 ) and 0.967 (under 1800 ) [40,43]. Additionally, the absence of imaginary frequencies confirmed that the optimized ted on a certain minima.…”

“…The optimized geometric structures related to minimum on the potential energy surface were provided by solving self-consistent field equation iteratively and optimizations were performed without any molecular restrictions. After the optimization, in order to confirm the convergence to minima on the potential surface and to evaluate the zero the present compounds were determined using analytic second derivatives with the B3LYP/6-31G(d) method and then scaled by 0.955 (above 1800 cm cm -1 ) [40,43]. Additionally, the structures are located on a certain energy distribution analysis (VEDA 4) program [44].…”

“…For the theoretical NMR investigations, the gauge including atomic orbitals/density functional theory (GIAO/DFT) approach is widely used for various types of compounds [23][24][25][26][27][28][29][30][31]. The DFT/B3LYP method exhibits good performance on electron affinities, excellent performance on bond energies and reasonably good performance on vibrational frequencies and geometries of inorganic or ionic compounds [32,33] as well as organic and neutral compounds [34][35][36][37][38][39][40].…”

Vibrational Spectroscopic Investigation and Conformational Analysis of Methacrylamidoantipyrine: A Comparative Density Functional Study

“…Vibrational spectroscopy has been widely used as the standard tool for structural characterization of molecular systems together with DFT calculations [7][8][9][10][11][12][13][14]. DFT is popular as it is a cost-effective procedure for studying the physical properties of molecules.…”

“…Unlike the Hartree Fock theory, DFT recovers electron correlation in the self-consistent KohnSham procedure through the functions of electron density, so it is a cost-effective and reliable method. The DFT/B3LYP model exhibits good performance particularly on vibrational frequencies and geometries of organic compounds [7][8][9][10][11][12][13][14].…”