GEDRAG & ORGANISATIE REVIEW - ISSN:0921-5077 http://lemma-tijdschriften.nl/ QUANTUM COMPUTATIONAL AND SPECTRAL INVESTIGATION OF 4-CHLORO PHENYLACETYL CHLORIDE V. George Fernandeza, Dr. B.Rajamannana*, Dr. S. Periandyb, K. Jayasheelab a Directorate of School Education, Anna Nagar, Puducherry 605 005. a* Department of Physics, FEAT, Annamalai University, Chidambaram, Tamil Nadu 608 002. b Department of Physics KMGIPGR, Pondicherry University, Puducherry 605 008 A B S T R A C T Spectral and quantum chemical studies have been undertaken on 4-Chloro phenyl acetyl chloride in this study. The Density Functional Theory (DFT), using B3LYP functional and 6-311++G (d,p) basis set, was used along with recorded spectra. Potential energy scan analyses were carried out to find out the stable conformers. FT-IR and FT-Raman spectra were recorded in the region of 4000-500 cm-1 for identification of all the fundamental modes of vibrations and were compared with the wave numbers predicted theoretically. The NBO, FMO analyses were carried out which were the most probable electronic transitions in the molecules. The prominent donor and acceptor orbitals were identified with their occupancy and hybridisation states. The structural analysis was carried out using the calculated bond lengths and bond angles and comparing it with the experimental values. The wave numbers were assigned using the PED values predicted. The atomic charges were calculated and were correlated with the experimental NMR chemical shift values. The most probable electronic transitions were tested experimentally using the recorded UV- vis spectrum and the oscillator strength and H-L contributions were analysed for such transitions. Docking studies were carried out to find out the antimutagenic activity of the molecule. Key words: FT-IR, FT-RAMAN, UV-analysis and DOCKING studies. Introduction Phenyl acetyl chloride is used as a key precursor in the total synthesis of vialinin B. It is employed as a linker to prepare den drimers and also used in the synthesis of various conjugated aromatic small molecules. Phenyl acetyl chloride is incompatible with strong oxidizing agents, alcohols, bases (including amines) may react vigorously or explosively if mixed with di-isopropyl ether or other ethers in the presence of trace amounts of metal salts[1]. It may cause severe burns to skin and eyes, when it its contacted with molten substances. Reaction with water or moist air will release toxic, corrosive or flammable gases. VOLUME 33 : ISSUE 02 - 2020 Page No:404 GEDRAG & ORGANISATIE REVIEW - ISSN:0921-5077 http://lemma-tijdschriften.nl/ Reaction with water may generate heat that will increase the concentration of fumes in the air. Contact with metals may evolve flammable hydrogen gas. Containers may explode when heated or if contaminated with water[2].The major use of chloroacetyl chloride is as an intermediate in the production of herbicides in the chloroacetanilide family including metolachlor, acetochlor, alachlor and butachlor. Some chloroacetyl chloride is also used to produce phenacyl chloride, another chemical intermediate, also used as tear gas. Phenacyl chloride is synthesized in a Friedel-Crafts acylation of benzene, with aluminium chloride as catalyst[3]. Experimental Methods The compound 4-Chloro phenylacetyl chloride was purchased from sigma Aldrich in spectroscopic grade and used for recording the spectra. The NMR 13C spectrum was recorded in the range of 20-200 ppm with the scanning interval of 20 ppm. The Hydrogen 1H NMR spectrum was recorded in region 1-10 ppm. The (CDCl3) chloroform solvent was used for recording both the spectra. The FT-IR spectrum was recorded by KBr pellet method on a Burker IFS 66V spectrometer in the range of 4000- 500 cm-1 with the spectra resolution of 2 cm-1. The FT- Raman spectrum was also recorded in the same instrument in the range of 4000- 500 cm-1 with FRA 106 Raman module equipped with Nd: YAG Laser with 200 mW powers. Ge detector with liquid nitrogen was used; the frequencies of all sharp bands are precise to 2 cm-1. The UV spectrum was recorded with the UV-1700 spectrophotometer, for the spectral wavelength range of 200- 400 nm for a scanning interval of about 0.2 nm. Computational Method The entire computations of the 4-Chloro phenylacetyl chloride were performed using the GAUSSIAN 09 software on Pentium IV processor [4] personal computer. The geometry of the titled compound was optimized using B3LYP functional with 6-311++G (d,p) basis set. The NMR chemical shift was carried out by GIAO functional along with B3LYP and 6-311++G (d,p) basis set combination. In addition, Mullikan atomic charges and natural charges of the title molecule were also computed using B3LYP method and same basis set. The optimized parameters of the compound were used for harmonic vibrational frequency calculations. The electronic properties such as NBO and HOMO-LUMO of the titled compound were calculated using time- dependent TD-SCF-B3LYP method under the same basis set. The dipole moment, the linear polarisability and first-order hyper polarisability of the title molecule were also computed using B3LYP method and same basis set. VOLUME 33 : ISSUE 02 - 2020 Page No:405 GEDRAG & ORGANISATIE REVIEW - ISSN:0921-5077 http://lemma-tijdschriften.nl/ Result and Discussion Conformational analysis The optimized molecular structure of the present molecule was used for conformational analysis, which was performed by potential energy surface scan techniques using B3LYP, by varying the dihedral angle 14CL-13C-12C-17H in the steps of 100 over one complete rotation. The graphical result, total energy (in Hartree) verses scan coordinates of the conformer is presented in Fig 13. The graph clearly shows that conformer at minimum energy level occurs at 1600 and 3100 with energy value -0.0622 and -0.0622 Hartree. This conformer serves as the most stable conformer of the compound. The maximum energy is observed for the conformer at 2450with energy value -0.0604 Hartree, this is the least stable or most unstable conformer of the compound. The most stable conformer is used for all the computations in the present work. Fig.1. Conformational analysis for 4-Chloro phenylacetyl chloride Structural analysis The structural analysis of 4-Chloro phenylacetyl chloride was carried out using B3LYP functional and 6-311++G (d,p) basis set for the most stable conformer of the compound. The bond lengths and bond angles of the compound calculated using this method is listed in the Table 1. The optimised structure of the compound is shown in Fig 2. VOLUME 33 : ISSUE 02 - 2020 Page No:406 GEDRAG & ORGANISATIE REVIEW - ISSN:0921-5077 http://lemma-tijdschriften.nl/ Fig.2. Optimized structure of 4-Chloro phenylacetyl chloride This compound has eight C-C, six C-H, one C-O, and two C-CL bonds. The C-C single bonds are expected to value around 1.45Å and the C=C double bond around 1.35 [5]. In the present molecule, in benzene ring, all the CC bonds have bond length values around 1.39 Å. This shows they are neither single bonded nor double bonded, which is due to the conjugation of the electrons among these bonds. The variation in values among them is due to the slight variation in distribution of electron density within the ring among these bonds, which is naturally due to both the substitutional groups with the benzene. In the case of acetyl chloride, the C3-C12 and C12-C13 bonds are found to have length of 1.5087 & 1.5181 Å. These values are higher than the expected range for CC single bond, and there is also difference between them, which are all naturally due to the presence of oxygen and chlorine atoms in this acetyl group. The tendency of oxygen atom is to attract an electron towards itself; hence, it redistributes the occupancy of electrons present with these CC bonds. According to the literature [6], the CO double bond is expected to have value 1.22Å and single bond 1.35Å respectively. In the present compound, the CO at C13=O15 is found to have bond length 1.17 Å, which is still less than the expected value for a double bond, which may be naturally due to the conjugation of chlorine in this group. All the CH bonds in the benzene ring structure are expected to be of length 1.08 Å [7]. In the present compound, CH bonds in the benzene ring are found to have values 1.08 Å and that in acetyl group 1.09 Å, the slight variation is purely due to the changed electron density at these bonds due to the presence of O and Cl atoms. There are two C-Cl bonds in this compound whose values are predicted to be 1.75Å in C6-Cl11 and 1.83Å in C13-Cl 14, the difference in values indicate the influence of O on this bond length. VOLUME 33 : ISSUE 02 - 2020 Page No:407 GEDRAG & ORGANISATIE REVIEW - ISSN:0921-5077 http://lemma-tijdschriften.nl/ The bond angle around each carbon atom is expected to be 120o [8]. In this molecule, the bond angle between C2-C1-H7, C4-C5-H10, C6-C5-H10, C2-C3-C12, C4-C3-C12 and C6-C1-H7 single bond angle are observed to be 120o as expected, but the other bond angles are varying between 118o-121o. Among the carbon atoms in the benzene ring, C6 at which the Cl is substituted shows much variation in the bond angles, whereas C3 at which the acetyl group is substituted, shows no variation in the angles, However, the carbon atoms in the acetyl group shows considerable variation from SP2 hybridisation value, which is naturally due to the electronegative atoms O and Cl.