Vibrational Spectroscopic and First Hyperpolarizability Study of 1-chloro-2-methyl-2-phenylpropane

C. Yohannan Panicker¹*, Hema Tresa Varghese² and Sheena Mary Y.²

¹Department of Physics, TKM College of Arts and Science, Kollam, Kerala, India.

²Department of Physics, Fatima Mata National College, Kollam, Kerala, India.

DOI : http://dx.doi.org/10.13005/msri/090123

ABSTRACT:

FTIR and FT-Raman spectrum of 1-chloro-2-methyl-2-phenylpropane were recorded and analyzed. The vibrational wavenumbers were examined theoretically using the Gaussian03 set of quantum chemistry codes. The experimental frequencies are in agreement with the calculated (B3LYP) scaled values. The predicted infrared intensities, Raman activities and first hyperpolarizability are reported.

KEYWORDS: DFT; Propane; Hyperpolarizability; FTIR; FT-Raman

Copy the following to cite this article: Panicker C. Y, Varghese H. T, Mary. Y S. Vibrational Spectroscopic and First Hyperpolarizability Study of 1-chloro-2-methyl-2-phenylpropane. Mat.Sci.Res.India;9(1)

Copy the following to cite this URL: Panicker C. Y, Varghese H. T, Mary. Y S. Vibrational Spectroscopic and First Hyperpolarizability Study of 1-chloro-2-methyl-2-phenylpropane. Mat.Sci.Res.India;9(1). Available from: http://www.materialsciencejournal.org/?p=1224

Introduction

Cumene is the common name for isopropylbenzene, an organic compound that is an aromatic hydrocarbon. It is a constituent of crude oil and refined fuels. It is a flammable colorless liquid that has a boiling point of 152°C. Nearly all the  cumene that is produced as a pure compound on an industrial scale is converted to cumene hydroperoxide, which is an intermediate in the synthesis of other industrially important chemicals, primarily phenol and acetone. Wood lignin’s heterogeneous structure consists not only of inter phenyl propane unit linakages of carbon to carbon and carbon to oxygen but also of side chains with various substituent and functional groups. The resin based dental polymers of phenyl propane derivatives have been investigated with the reinforcing effect of electrospun nylon nanofibres.¹ It was found that the fibres have a crystalline structure and are mechanically strong. The small diameter of nanofibres also provide a high ratio of surface area to volume, which could enhance the intermolecular hydrogen bonding between the filler of nylon nanofibres and the matrix of resin polymers. Dauban et al.,² reported the synthesis of phenylpropane derivatives and its calcimimetics properties. Blends of phenylpropane derivatives have been widely investigated because of the theoretical and practical importance of these high performance polymers.³ From the the very initial studies, it was claimed that miscibility occurs a wide composition range, as the blends displayed single intermediate glass transitions in the differential scanning calorimetry heating.⁴ Further studies revealed phase separation upon annealing^5,6 and the phase behaviour of the systems found to be dependent on derivatives and thermal history. There are several examples of optically active phenylpropanols as the pharmacophore in the biological active compounds or as the key intermediates to construct these interesting skeletons. Such as a marketed anti-cholesterolemia drug ezetimibe,⁷ the well known anti-depressant drug fluoxetine,⁸ 2-substituted chroman derivatives of alpha-tocopherol (vitamin E) (pinostrobin and tephrowatsin E from natural sources),⁹ chemokine receptor modulators,¹⁰ proteinkinase inhibitors (useful for the treatment of neoplasms and viral infection)¹¹ and antagonist (investigated to be safer anti-obesity agents).¹² In the present study the FT- IR and FT-Raman and theoretical calculations of the wavenumbers of the title compound are reported.

Experimental

The FT-IR spectrum was recorded on a DR/Jasco FT-IR 6300 spectrometer and the FT- Raman spectrum was obtained on a BRUKER RFS 100/S, Germany. For excitation of the spectrum the emission of a Nd:YAG laser was used, excitation wavelength 1064 nm, maximal power 150 mW. One thousand scans were accumulated with a total registration time of about 30 min. The spectral resolution after apodization was 2 cm^-1.

Computational Details

Calculations of the title compound were carried out with Gaussian03 software program¹³ using the B3LYP/6-31G* basis sets to predict the molecular structure and vibrational wavenumbers. The DFT hybrid B3LYP functional tends also to overestimate the fundamental modes; therefore scaling factors have to be used for obtaining a considerably better agreement with experimental data. Therefore, a scaling factor of 0.9613 was uniformly applied to the DFT calculated  wavenumbers.¹⁴ The assignment of the calculated wavenumbers is aided by the animation option of MOLEKEL program, which gives a visual presentation of the vibrational modes.^15,16

Figure 1:

Click on image to enlarge

Results And Discussion

The observed IR, Raman and calculated (scaled) wavenumbers and the assignments are given in Table 1. In aromatic compounds the asymmetric stretching vibrations of CH3 are expected^17,18 in the range 2950-3050 cm^-1 and symmetric CH₃ vibrations in the range of 2860-3000 cm^-1. The first of these results from the asymmetric stretching u_asCH₃ mode in which two C-H bonds of the methyl group are extending while the third one is contracting. The second arises from the symmetrical stretching u_sCH₃ in which all three of the C-H bonds extend and contract in phase. The asymmetric stretching modes of the methyl group are calculated (DFT) to be 3067, 3028, 3022, 3014 cm^-1 and the symmetric mode at 3006, 2942 cm^-1. The bands observed at 3061, 3026, 2970 cm^-1 in the IR spectrum and 3069, 2948 cm^-1 in the Raman spectrum are assigned as stretching modes of the methyl group. Two bending can occur within a methyl group. The first of these, the symmetrical bending vibration, involves the in-phase bending of the C-H bonds. The second, the asymmetrical bending vibration, involves out-of-phase bending of the C-H bonds. The asymmetrical deformations are expected in the range¹⁷ 1400-1485 cm^-1. The calculated values (DFT) of dasCH₃ modes are at 1503, 1495, 1491, 1483 cm^-1. In many molecules, the symmetric deformations dsCH₃ appears with an intensity varying from medium to strong and expected in the range17 1380 ± 25 cm^-1. The DFT calculations give δ_asCH₃  mode at 1411 and 1393 cm^-1. Aromatic molecules display a methyl rock¹⁷ in the neighborhood 1045 cm^-1. The second rock¹⁷ in the region 970±70 cm^-1 is more difficult to find among the C-H out-of-plane deformations. In the present case, these rCH₃ modes are calculated at 1178, 1104, 1027 and 1018 cm^-1. The bands observed at 1111, 1033 cm^-1 in the IR spectrum and at 1182, 1108, 1033 cm^-1 in the Raman spectrum are assigned as rocking modes of the methyl group. The methyl torsions often assigned in the region¹⁷ 185 ± 65 cm^-1.

---

This work is licensed under a Creative Commons Attribution 4.0 International License.