An International Quarterly Research Journal

ACL

                                                                                                       ISSN : 0971 - 9822

                                                                           Vol 19,  No 3&4,  July-December, 2015

Asian Chemistry Letters                                                                                                     Vol. 19, No. 3&4 (2015) 97-112


Infrared spectrum, vibrational assignments, normal coordinate analysis and quantum mechanical

calculations of (4-chloro-2-fluorophenyl)boronic acid

 

Usama A Soliman1,2, Ibrahim A Shaaban1 and Tarek A Mohamed1

1Department of Chemistry, Faculty of Science, Al-Azhar University, Nasr City, Cairo 11884, Egypt 2Preparatory Year Deanship,

Department of Chemistry, Jazan University, Jazan 82621, Saudi Arabia

___________________________________________________________________________________________________________________________________

Geometry, vibrational frequencies and thermodynamic parameters of 4-chloro-2-florophenylboronic acid (CFPB; C6H5BClFO2) have been computed theoretically using Gaussian 03 software. Initially, four rotamers were suggested for the titled compound resulting from the internal rotation of hydroxyl group around C–B bond Energies. Thus, the conformational stabilities were computed and analyzed for an isolated CFPB molecule using B3LYP functional utilizing the standard 6-311++G(d,p) basis set. The results of calculations predict CT structure (one OH is cis towards both phynyl C1 and F atoms while the other OH is trans to phenyl C1 atom) to be the most stable conformation owing to O5…H14 and F6….H15 intra-molecular hydrogen bonding. In order to assign the observed frequencies vis the estimated ones, a normal coordinate analysis has been performed for the expected vibrations with respect to the nuclei displacements. The calculated wave numbers and intensities of CT form are in good agreement with those observed experimentally. ©Anita Publications. All rights reserved.

Keywords: 4-chloro-2-florophenylboronic acid, B3LYP calculations, Infrared spectroscopy, Normal coordinates analysis

Infrared spectrum, vibrational assignments, normal coordinate analysis and quantum mechanical calculations of (4-chloro-2-luorophenyl) boronic acid.pdf
Usama A Soliman, Ibrahim A Shaaban and Tarek A Mohamed

___________________________________________________________________________________________________________________________________


Asian Chemistry Letters                                                                                               Vol. 19, No. 3&4 (2015) 113-124


 Raman spectral transitions and barriers to internal rotations of methylmethoxysilanes

using MP2 and B3LYP calculations


Tarek A Mohamed*, Ibrahim A Shaaban, Ahmed M Abuelela, and Usama A Soliman

Department of Chemistry, Faculty of Science (Men’s Campus)

Al-Azhar University, Nasr City 11884, Cairo, Egypt

___________________________________________________________________________________________________________________________________

DFT- B3LYP and ab intio MP2 at 6-31G(d,p) basis set have been used to compute the equilibrium geometry and vibrational frequencies for methylmethoxysilanes; (CH3)nSi(OCH3)4 – n , where n = 0,1,2,3 and 4. Aided by the calculated wavenumbers, Raman activity, force constants and normal coordinate analysis in addition to previously recorded Raman spectra, we have discussed the vibrational analysis, correlation and spectral transitions for backbone skeleton normal modes based on Td for C4Si and SiO4, C3v for C3SiO and CSiO3, and C2v for C2SiO2 regardless of overall symmetry for the series. The Si–C symmetric stretch (A1) undergoes a blue shift owing to the simultaneous decrease of the methyl groups; ν SiC > vs SiC2 > νs SiC3 > vs SiC4, however the trend was reversed in case of SiO antisymmetric stretch; νas SiO4 > νas SiO3 > νas SiO2 > ν SiO. Structural correlations are observed for Si–C and Si–O bond distances and CSiC angle is inversely proportional to the number of methoxy groups in the investigated series, however, OSiO angle is directly proportional. Finally, CH3 and OCH3 barriers to internal rotation for the methylmethoxysilanes were carried out using B3LYP/6-31G(d,p) optimized structural parameters where the CH3 and OCH3 barriers are directly proportional to the number of CH3 and OCH3 groups, respectively. Our results are discussed herein and compared to similar molecules whenever appropriate.©Anita Publications. All rights reserved.

ramanspectraltransitionsandbarrierstointernalrotationsofmethylmethoxysilanesusingmp2andb3lypcalculations.pdf
Enter file download description here

___________________________________________________________________________________________________________________________________


Asian Chemistry Letters                                                                                               Vol. 19, No. 3&4 (2015) 125-136


Vibrational spectral investigations of L-Methioninium acetate


G Edwin Sheelaa,c, D Manimaranb, I Hubert Joeb*, and V Bena Jothyc
aDepartment of Physics, Muslim Arts College, Thiruvithancode-629 174, India
bCentre for Molecular and Biophysics Research, Department of Physics, Mar Ivanios College, Thiruvananthapuram-695 015, India
cDepartment of Physics, Women’s Christian College, Nagercoil-629 001, India

___________________________________________________________________________________________________________________________________

L-Methioninium acetate (LMA) crystals were grown by slow evaporation technique. FT-IR and FT-Raman spectra of LMA crystal have been recorded and analyzed. Molecular structure and vibrational harmonic wavenumbers of the title compound were obtained by DFT (B3LYP) employing 6-311++G (d,p) basis sets. The detailed interpretation of vibrational spectra was carried out with the aid of normal coordinate analysis on the basis of potential energy distribution using MOLVIB program. Stability of molecule arising from hyperconjugative interactions and charge delocalization have been analyzed using natural bond orbital analysis. First-order hyperpolarizability, HOMO-LUMO energy were also calculated. HOMO-LUMO energy gap reflects the chemical activity of the molecule. The first-order hyperpolarizability value βtot of LMA is equal to 243.95×10-31 e.s.u, which is 31 times that of urea, indicating its NLO activity. © Anita Publications. All rights reserved.
Keywords: FTIR; FT-Raman; DFT; NLO; HOMO-LUMO.

Vibrational spectral investigations of L-Methioninium acetate.pdf
G Edwin Sheela, D Manimaran, I Hubert Joe, and V Bena Jothy

___________________________________________________________________________________________________________________________________