Vol. 22, No. 4 (2013) 335-347

The utilization of rare gas solution for making vibrational assignments and conformation stability determinations of three membered rings

James R Durig*, Bhushan S Deodhar,  and Joshua J Klaassen
Department of Chemistry, University of Missouri-Kansas City, Kansas City, MO 64110 USA

The use of rare gas solutions in the field of vibrational spectroscopy has been rather slow to develop for several reasons. Firstly, rare gases are liquids only at relatively low temperatures which requires infrared and Raman cells be maintained at relative low temperatures during the experiment. Therefore, the use of rare gas solutions to obtain spectroscopic data is not routine. Another disadvantage is the solubility in rare gas solutions is relatively low and rather poor for very polar molecules. Nevertheless there are a number of advantages for many samples which makes rare gas solutions good. For example, there is very little interaction of the solvent with solute molecules so the frequencies observed for the bands in solution are hardly shifted from the values observed in the gas. Also the rare gases do not absorb infrared radiation so it is possible to use infrared liquid cells with path lengths of several centimeters such as 10 cm. Thus the solutions can be very dilute i.e. 10^-4 molar, which drastically reduces the association of the solute molecules. Therefore variable temperature studies can be carried out on alcohols, amines, and acids where it is nearly impossible with conventional solvents. In fact it is nearly impossible to obtain enthalpy differences for these molecules with conventional solvents. Therefore some examples will be provided which will demonstrate the ability to determine conformational stabilities and vibrational assignments.© Anita Publications. All rights reserved.

Total Refs: 27

Vol. 22, No 4 (2013) 349-361

The FT-IR and FT-Raman spectra, and  other molecular properties  of 5-bromo-2-furoic acid hydrogen bonded dimer

V Balachandran^a, S Lalitha^b, and S Rajeswari^b
aCentre for Research, Department of Physics, A A Government Arts College, Musiri 621 211, India
^bP.G. & Research Department of Physics, Periyar EVR College(Autonomous), Tiruchirappalli-620 023, India

The FTIR and FT-Raman spectra of 5-bromo-2-furoic acid have been measured in the range of 4000-400 cm^-1 and 4000-100 cm^-1, respectively. Quantum chemical  calculations of energies, geometries, and vibrational wavenumbers of 5-bromo-2-furoic acid (5B2FA) have been carried out using HF and DFT/B3LYP methods with 6-31+G(d,p) basis set. The optimized geometrical parameters obtained by B3LYP method show good agreement with experimental data. The differences between the observed and scaled wavenumbers of most of the fundamentals are very small. A detailed interpretation of the theoretical spectra of 5-bromo-2-furoic acid was also reported for monomer and dimer forms. Existence of intermolecular hydrogen bondings through COOH group gives the evidence for the formation of dimer entities in the title molecule. The calculated HOMO and LUMO energies show atomic orbital overlapping and charge transfer occurs within the molecule. A detailed molecular picture of 5B2FA and its intermolecular interactions were obtained from NBO analysis. The temperature dependence of various thermodynamic parameters was also studied. © Anita Publications. All rights reserved.
Total Refs : 34

 Vol. 22, No 4 (2013) 363-376

FT-IR, FT-Raman, molecular geometry, vibrational assignments, ab initio and density functional theory calculations for 4-hydroxy-2,6-dimethyl pyrimidine

A Janaki^a, V Balachandran^b and A Lakshmi^c
aDepartment of Physics, Govt. Arts College for Women (Autonomous), Pudukkottai-622 001, India
^bCentre for Research, Department of Physics, A A Government Arts College, Musiri, Tiruchirappalli-621 211, India
^cDepartment of Physics, Govt. Arts College , Trichy  620 022, India

Fourier transform Raman and infrared spectra of 4-hydroxy-2,6-dimethyl pyrimidine (HDMP) were recorded and interpreted by comparison with respective theoretical spectra calculated using HF and B3LYP methods. The HDMP equilibrium geometry with Cs symmetry, harmonic vibrational frequencies, infrared and Raman intensities were determined. The band assignments were based on potential energy distribution (PED) of normal modes. In the computed equilibrium geometries, the bond lengths and bond angles show changes in the neighborhood of methyl and hydroxyl substituent. The molecular stability and delocalization of electron density of atoms were investigated by applying the Natural Bond Orbital analysis (NBO). The dipole moment, polarizability and the hyperpolarizability values of the investigated molecule have been computed using HF and B3LYP methods. © Anita Publications. All rights reserved.
Total Refs : 47