Experimental and theoretical spectroscopic investigations of 4-Bromo-3-methylbenzonitrile

October December 2017 1572 JCPS Volume 10 Issue 4 Experimental and theoretical spectroscopic investigations of 4-Bromo-3-methylbenzonitrile A Ajaypraveenkumar, Shajikumar, R. Ganapathi Raman* Department of Physics, Department of Nano Technology, Noorul Islam Centre for Higher Education, Kumaracoil 629 180, Tamilnadu, India. ∗Corresponding author: E-Mail: ganapathiraman83@gmail.com ABSTRACT The experimental and theoretical studies of 4-Bromo-3-methylbenzonitrile (4B3MBN) were inspected for electronic structure, vibrational and other properties by Density Functional Theory (DFT). The FTIR (4000– 400 cm) and FT-Raman (FTR) (3500–50 cm) spectra of 4B3MBN were recorded in the liquid phase (acetone). The molecular geometry and vibrational frequencies of 4B3MBN in the ground state have been calculated by using the theoretical methods (B3LYP) invoking a basis set. In addition, Molecular electrostatic potential (MEP) and atomic charges of carbon, nitrogen and oxygen were calculated. Moreover, thermodynamic properties of the title compound were predicted by computational methods.


INTRODUCTION
The many organic molecules investigated for future applications through the experimental as well as the theoretical methods in the various twigs of the science and engineering (Arockiasamy Ajaypraveenkumar, 2017).The theoretical methods have the fast and furious results for the larger molecules to evaluate the applications in addition to their physicochemical properties.The computational techniques powerful tool for the pin pointed answers for the molecules, So as to corroborate and yet expand the experimental results.It is a vast and versatile component in the chemicals, which is called cyanobenzone or phenyl cyanide.The special benzonitrile derivatives like organic acids (benzoic acid, mandelic acid), amines (benzyl amine, pyridine), neutrals (benzonitrile, toluene) and benzonitrile herbicides.Benzonitrile is an applicable as solvent and precursor to number of derivatives.One of the benzonitrile derivatives is used in Pharmaceutical and Agrochemical Intermediates, Epoxy curing agent.Moreover Benzonitrile is mainly used for the agriculture fields, which households to control the growth of weeds and their residues persist in the environment (Arockiasamy Ajaypraveenkumar, 2017).
Benzonitrile compound is the best solvent in the chemical and physical laboratories.Because of benzene has an aprotic polar molecule with a dipole moment of 4.18Debye.The properties enhanced while added the substituted roles to the benzene.The substitution benzonitrile compounds had weak effect and strong inhibitory effect as a consequence of its position.The catalytic rate of the nitrilase enzyme is the vast cause for the weak effect in the meta or para position of benzonitrile.In the ortho position of the benzonitrile has strong effect due to steric hindrance (Murugan, 2012).Benzonitrile is used as antiseptic, anti-urinary, pharmaceutical, agrochemical intermediates, epoxy curing agent and dye sensitizers etc.
The title compound 4B3MBN is almost planar and the derivatives are used like midways in the production of phthalocyanine dyes.The surrogated phthalocyanine dyes are used for DSSC, photo redox responses and photodynamic cancer therapy (Arockiasamy Ajaypraveenkumar, 2017).To the best of our knowledge, the vibrational assignments and other properties never determined for this compound still now.So this article going to serve about complete vibrational assignments of different modes of molecules.And electronic and thermo studies are simultaneously take over to the molecule.

METHODOLOGY General:
The molecule 4-Bromo-3-methylbenzonitrile (4B3MBN) of spectral grade was purchased from sigma Aldrich Chemical Co.U.S.A, in powder form and was used as such without further purification.Spectral measurements: The spectroscopic analytical purpose, The Fourier-transform infrared (FTIR) and The Fourier-transform Raman (FT Raman) spectra have been recorded at normal temperature in the region 400-4000cm -1 and 50-3500cm -1 respectively.Infrared spectrum recorded using 8400S Bruker, Alpha T, and Germany infrared spectrophotometer with scanning speed of 30 cm -1 min -1 the spectra are traced.FT Raman spectrum has been recorded using 1064nm line of Nd: YAG laser as excitation wavelength on an EZRaman, Enwaveoptronics, and USA IFS 66 V spectrometer.All spectra recorded out at our campus of the Nanotechnology Department.The spectra are exposed in figures.3& 4. Computational Details: The Gaussian 09W software package has been used for predicting the whole vibrational assignments and optimized geometrical parameters of 4B3MBN with the original version (Alen, 2015).The complete geometry parameter has been derived from B3LYP is the three parameter functional by way of applying ab-initio Becke-Lee-Yang-Parr hybrid method (Govidasamy, 2014) on Intel Core i3 3.3GHz processor personal computer (Frisch, 2009).The total energy distribution (TED) was calculated and explained using the Scaled quantum mechanical program using VEDA.4.0.Software (Diwaker, 2015) and vibrational modes also calculated through their TED.From the second derivatives of the energy has calculated the FT-IR, Raman frequencies are computing and intensities plots are done by the Gauss sum program.
The MEP map had been drawn and Mulliken atomic charge distribution (MA) & Thermo dynamical parameters are resolute by Gaussian 09W software package.

RESULTS AND DISCUSSIONS
Optimized geometry: The B3LYP/6311++G (d, p) energy values are most probable global minimum energy and good agreement with experiment data (Muhammad Shahid, 2009).Table .1,shows the equilibrium geometry parameters of the 4B3MBN molecule for two dissimilar basis sets.0.167236 CH vibrations: Four kinds of CH moieties are calculated in the title compound 4B3MBN.In this CH moieties have been listed, six υCH and βCH as well as three torsion and δ bending vibrations.The scenery of the substituent does not align because of these stretching vibrations.The stretching has most feasible frequency between the region at 3100-3000cm -1 (Parr, 1983;Premkumar, 2014).The calculated stretching vibrations of the title compound region, in between 3301 -2431cm -1 .The experimental frequencies have been observed at the regions 1698, 2319 cm -1 .The CH stretching and β bending vibrations are incorporate with each other.The calculated CH β bending vibrations of 4B3MBN occurs in the region of 1233-1017cm -1 and observed FTIR and FTR spectra at 1023 cm -1 and 1040 cm -1 , respectively.The CH δ bending transpires at the region 950-800cm -1 generally.The analyzed δ bending vibrations of 4B3MBN are found at 815, 941, 965 cm -1 and observed in FTIR arises in the region 811, 888cm -1 .In this case, the δ bending has been merged with the torsion vibrations.Calculate and observed values good agreement with each other.CBr vibrations: CBr moieties tabulated on the root of calculated energy distribution and separated three kinds of styles.Two stretching and three in-plane bending vibrations are packed in the CBr atom.In the literature survey, the authors assigned vibrations frequency range of 1129-480 cm -1 while the Carbon interactions with others heavy atoms like Cl, Br, I (Mooney, 1964).The 4B3MBN compound has the strong stretching vibrations in the region of 254, 522 and 1040 cm -1 found from Raman spectrum.Bending vibrations in the FTR spectra occurs in the range of 134, 380 cm -1 and the calculated frequency of the title molecule transpire in the range at 135, 219, 361cm -1 .These vibrations are very well agreed with literature survey (Sundaraganesan, 2005).CN vibrations: In the CN moieties, stretching frequency is the intensively localized one due to the TED for this frequency contains good contribution from that constant value of stretching force.The benzonitrile compound wavenumbers of stretching vibrations fall in the range 2220-2240cm -1 (Dollish, 1974).IR intensity modulated depends upon add the substituent to the benzonitrile.In this research compound has been identified at 2338 and 2217cm -1 in Raman and FTIR spectra respectively.The calculated wavenumbers of stretching vibrations at 2331cm -1 coincide with the Raman value.This is the ideal frequency of the whole molecule which confirmed the CN stretching with 89% assignment.The bending vibrations (β) of the title molecule spotted at 134, 380, 548 cm -1 in Raman spectra.These experiment values are well agreement with the calculated frequencies.CC vibrations: There are six equivalents and two out of CC bonding in the 4B3MBN compound and totally eight CC stretching vibrations exist.Generally, the benzene ring υCC vibrational modes fall in the constituency 1650-1200cm -1 (Varsanyi, 1974).The title compound υCC vibrations are found in the regions at 1203, 1375, 1428, 1459,  1541, 1648, 2217cm -1 and 712, 1040, 1250, 1374, 1416, 1612cm -1 (735, 965, 1022, 1141, 1170, 1209, 1283, 1315,  1343, 1411, 1492, 1569, 1612, 2331cm -1 by theoretically) through IR & Raman spectra, correspondingly.In addition, some other modes are couples with CC bending vibrations (β) are found in the regions at 1023cm -1 and 2217cm -1 (1022, 2231cm -1 by theoretically) through spectra respectively.CCCC torsional vibrations: The ring torsions have been assigned in the region at below 800cm-1 which is discussed in present paper referred by earlier reports (Rastogi, 2010).The IR and Raman spectra peak observe in the regions at 578, 627 cm -1 and 496, 572 cm -1 , respectively.These peaks have been calculated at the region at 73, 144, 208, 277, 402, 472, 580,

Figure.2. Mulliken charges comparison of two basis sets for 4B3MBN
Figure.1, shows the computerized structure of the 4B3MBN molecule with same basis set.The length should be increased between every atom in the calculated values while compared with experimental values because of substituent of the title molecule.The length and angle of the Br substituent are longer value 1.91Å in all other compound bonding.Carbon interactions are short value in the whole molecule.These effects are qualified for the intra charge transformations (ICT) for stability of the molecule.

Figure. 1 .
Figure.1.Optimized structure of 4B3MBN -C9-C6 0 C5-C8-C9-H16 180 H15-C8-C9-C6 180 H15-C8-C9-H16 0 a -Farrugia (1997), b -Farrugia (1999), c -Johnson (1941) Charge analysis: The charges are computed by MA with same basic sets tabulated in table.3.MA graph of 4B3MBN molecule has been drawn in the figure.2.MA charges are the main impact for the functions like as quantum mechanical calculations, electronic effects, polarizability changes, Dipole moments and other properties of the molecules.The polarization changes decided the charges by the different basis sets.In this research molecule, Carbon atom has both sign values in two methods.The positive charge distribution of Hydrogen atoms are acts as an acceptors, and the opposite trends of the atoms Nitrogen, Bromine are acts as a donor.Conclude from the overall comparison, (2d, p) basis sets atoms charge distribution values are higher than (d, p).

Figure. 5 .
Figure.5.Electrostatic potential map & Counter map for 4B3MBN Molecular electrostatic potential: The visual representations are the mostly welcomed one compared with other studies.Molecular electrostatic potential (MEP) is the versatile used visual illustration for find out the reactivity of the molecule which explains through its colors (Prasad, 2015), hydrogen bonding interactions and biological detection methods (Apoorva Dwivedi, 2014).The electrophilic and nucleophilic attacks are demonstrated by two different colors.The MEP's of 4B3MBN calculated and drawn by the computational method in Figure. 5.The colors are increased the order of red, yellow, green, blue.The red color starts from negative region for electrophilic reactivity and blue ends with positive region for nucleophilic reactivity regions.The values of the regions increased from red to blue (-9.944 to 9.944) for the title molecule.The carbon, nitrogen and Bromine groups are almost negative electrostatic potential for electrophilic attack.The hydrogen atoms are the positive one for nucleophilic attack.The Mulliken population analysis is showing the electronic charges distribution of the molecules which identified the support of MEP maps.Table.4.Thermodynamical parameters of 4B3MBN Thermodynamic parameters B3LYP Thermodynamic parameters B3LYP Self-consistent field energy (a.u) -2937.178Specific heat capacity at constant volume (cal/mol K) Zero point vibrational energy (kcal/mol) 67.773Total 34.125