The (DFNB) 1, 2 Dichloro-4-fluoro-5- Nitrobenzene structured to density functional theorystudies using B3LYP/6-31+G (d,p) method. Characterization was done by FT-IR ,FT Raman andNMR spectroscopy techniques. Molecular electrostatic potential study was also determined

R, Purushothaman

English

Scholar

VIBRATIONAL INVESTIGATION, MOLECULAR STRUCTURE OF 1, 2 DICHLORO-4-FLUORO-5- NITROBENZENEDr.R.Purushothaman1., Dr.K.N.Chadambarakumar2.,Dr.K.Ezhumalai3.,Ms.R.Ramya4.Assistant professor Department of physicsDhanalakshmi Srinivasan College of arts and science for women (autonomous)Perambalur- 621212ABSTRACTThe (DFNB) 1, 2 Dichloro-4-fluoro-5- Nitrobenzene structured to density functional theorystudies using B3LYP/6-31+G (d,p) method. Characterization was done by FT-IR ,FT Raman andNMR spectroscopy techniques. Molecular electrostatic potential study was also determined.INTRODUCTION:Nitrobenzene very poisonous, flammable, pale yellow and liquid aromatic compoundwith an odor like that of bitter almonds. It is sometimes called oil of mirbane or nitrobenzol.Nitrobenzene melts at 5.85°C, boils at 210.9°C is only slightly soluble in water but is verysoluble in ethanol, ether and benzene. Nitrobenzene is prepared by treating benzene with amixture of nitric and sulfuric acid in the resulting nitration reaction one hydrogen in the benzenemolecule is replaced with a nitro group.The major use of nitrobenzene is in the production of aniline, commercially the mostimportant amine. Nitrobenzene is heated with iron and dilute hydrochloric acid and the resultinganilinium chloride is treated with sodium carbonate to release aniline. In the pharmaceuticalindustry nitrobenzene is used in the production of the analgesic acetaminophen or paracetamol.Nitrobenzene is also used in shoe and floor polishes, leather dressings and paint solvents to maskunpleasant odors. As oil of mirbane, nitrobenzene was used as an inexpensive perfume for soapsand cosmetics but is now considered too toxic for such applications.The compound 1, 2-Dichloro-4-fluoro-5-Nitrobenzene (DFNB) is used as a reagent forthe detection and determination of nicotinic acid, nicotinamide and other pyridine compounds. Itis also used in the manufacture of azo dyes, fungicides, rubber chemicals and explosives and asan algicide in coolant water of air conditioning systems. Contact sensitizations with DFNB havebeen used as a measure of cellular immunity.Various spectroscopic studies of halogen and nitrogen substituted benzene compoundshave been reported in the literature. DFNB belongs to the group of organic halogen compoundsreplacing two hydrogen atoms in benzene by methyl (CH3) and a nitro group (NO2). Literaturesurvey reveals that no detailed B3LYP with 6-31+G(d,p) basis set of FT-IR, FT-Raman andNMR (13C and 1H) chemical shifts calculation of DFNB have been reported so far. It is, thereforethought worth to make this theoretical and experimental vibrational spectroscopic research basedon molecular structure to give the correct assignment of fundamental bands in the experimentallyobserved FT-IR and FT-Raman spectra. In this study, molecular geometry and vibrationalfrequencies are calculated using hybrid density functional method. This method predictsrelatively accurate molecular structure and vibrational spectra with moderate computationaleffort.2. Experimental DetailsThe fine sample of 1, 2-Dichloro-4-fluoro-5-Nitrobenzene (DFNB) is purchased fromSigma-Aldrich chemicals, USA and it was used as such without any further purification. The FT-IR spectrum of the compound has been recorded in Perkin-Elmer 180 spectrometer in the rangeof 4000–400 cm−1. The spectral resolution is ±2 cm−1. The FT-Raman spectrum of the compoundwas also recorded in same instrument with FRA 106 Raman module equipped with Nd: YAGlaser source operating in the region 3500–100 cm−1 at 1064 nm line width with 200 Mw powers.13C and 1H NMR spectra were taken in CDCl3 solutions and all signals were referenced to TMSon a BRUKER TPX-400 FT-NMR spectrometer.3. Computational DetailsThe molecular structure of the DFNB molecule in the ground state is computed byB3LYP/6-31+G (d,p) method. The optimized structural parameters are used in the vibrationalfrequency calculations at B3LYP level. The DFT calculations were carried out for DFNB withGAUSSIAN 09W program package. Initial geometry generated from the standard geometricalparameters was minimized without any constraint, which invokes Becke’s three parameterhybrid method with Lee-Yang-Parr correlation functional (LYP), implemented with the samebasis set for better description of the bonding properties. All the parameters were allowed torelax and all the calculations converged to an optimized geometry which corresponds to a trueminimum, as revealed by the lack of imaginary values in the wave number calculations. TheCartesian representation of the theoretical force constants have been computed at the fullyoptimized geometry.The multiple scaling of the force constants were performed according to scaled quantummechanical (SQM) procedure using linear scaling in the natural internal coordinaterepresentation. Transformation of force field, the subsequent normal coordinate analysis (NCA)including the least square refinement of the scale factors and calculation of the total energydistribution (TED) were done on a PC with the MOLVIB program (version V7.0-G77) writtenby Sundius .The calculated frequencies are scaled by 0.9689 scale factor. As a result, theunscaled frequencies, reduced masses, force constants, infrared intensities and Raman activitieswere obtained. The systematic comparison of the results from DFT theory with results ofexperiments has shown that the method using B3LYP functional is the most promising inproviding correct vibrational wave numbers.4. Results and Discussion4.1. Vibrational assignmentsThe labeling of atoms of DFNB is shown in Fig. 1. The molecule contains two Cland a NO2 group connected with benzene ring. Experimental and simulated spectra of FT-IR andFT-Raman are presented in Figs. 2 and 3, respectively.The DFNB molecule consists of 14 atoms, which undergoes 36 normal modes ofvibrations. On the assumption of C1 group of symmetry, the numbers of vibration modes of the36 fundamental vibrations of the molecule are distributed as 25 in-plane and 11 out-of-planevibrations of same symmetry species.The vibrational frequencies calculated at B3LYP level are scaled by 0.905 and the range of wavenumbers above 1700 cm–1 are scaled as 0.958 and below 1700 cm–1 scaled as 0.983 for titlecompound. After scaled with the scaling factor, the deviation from the experiments is less than10 cm–1 with a few exceptions. The force fields determined were used to calculate the vibrationaltotal energy distribution (TED) among the normal coordinates.3000 2500 2000 1500 1000 400Wavenumber (cm-1)Fig.2. Comparison of experimental and calculated spectra of DFNB.2500 2000 1500 1000 500Wavenumber (cm-1)Fig.3. Comparison of experimental and calculated spectra of DFNB.The observed FT-IR, FT-Raman and theoretically calculated frequencies by B3LYP/6-31+G(d,p) method along with Table their assignments, IR intensities (Km mol‒1) andRaman intensities (Å4 amu‒1) of DFNB.No.Observed wavenumbers(cm‒1)Calculated wavenumbers(cm‒1)IRIntensities Raman VibrationalFT-IR FT-Raman Unscaled Scaled intensities Assignments1 1800(s) 1709 1693 246.38 11.80 NO2asym(98)2 1600(vw) 1658 1584 78.21 64.62 NO2sym(95)3 1625(s) 1625 1544 33.83 60.61 CC(92)4 1500(m) 1518 1485 186.57 1.01 CC(89)5 1425(w) 1425(vw) 1425 1401 111.02 61.16 CC(88)6 1360(w) 1400(s) 1413 1396 213.22 143.64 CC(84)7 1311(w) 1349 1318 26.14 3.46 CC(82)8 1309 1285 72.77 47.12 CC(81)9 1250(m) 1260(vw) 1241 1202 2.99 0.92 CH(71)10 1170(vw) 1168 1121 92.84 39.45 CH(75)11 1100(s) 1150(vs) 1125 1104 4.25 2.76 CF(65)12 1060(m) 970(m) 975 956 80.32 1.92 CN(61)13 930 905 23.21 1.01 CH(56)14 864 845 17.01 3.04 CCl(60)15 800(vw) 863 831 18.35 7.78 CCl(52)16 764 712 12.59 1.84 NO2rock(54)17 740(m) 734 711 38.22 1.74 CH(51)18 694 654 29.59 9.91 NO2sciss(59)19 630(vw) 664 633 0.01 0.23 CCl(52)20 619 592 1.08 0.37 CN(51)21 610(vw) 611 574 2.42 1.96 CCl(51)22 500(vw) 537 512 9.59 0.76 NO2wagg(43)1.1. C-H vibrationsIn benzene like molecule C‒H in-plane bending vibrations interact with C‒C stretchingvibrations and are observed as a number of bands in the region 1000–1300 cm‒1. The FT-IR bandidentified at 1250(m) cm‒1 and FT-Raman band at 1260(vw), 1170(vw) cm‒1 were assigned toC‒H in-plane bending vibration of DFNB.The C‒H out-of-plane bending vibrations occur in the region 900–667 cm‒1. The bandsobserved at 740(m) cm‒1 in FT-Raman spectrum of DFNB. The theoretically calculated valuesfor C–H vibrational modes by B3LYP/6-31+G(d,p) method gives good agreement withexperimental data.4.1.2. Ring VibrationsMost of the ring vibrational modes are affected by the substitutions of functional groups.The characteristic ring stretching vibrations are assigned in the region 1650–1300 cm‒1 [25].Therefore, the C–C stretching vibrations of DFNB are found at 1625(s), 1500(m), 1425(w),1360(w) in FT-IR spectrum and 1425(vw), 1400(s), 1311(w) in FT-Raman spectrum for DFNB.The theoretically computed values for C–C vibrational modes by B3LYP/6-31+G(d,p) methodgives excellent agreement with experimental data. Small changes in wavenumber observed forthese modes are due to the changes in force constant/reduced mass, resulting mainly due toaddition of fluorine group to nitro.4.1.3. C‒Cl vibrationsThe vibrations belonging to the bond between the ring and the halogen atoms are worthto discuss here, since mixing of vibrations is possible due to the presence of heavy atoms on theperiphery of the title molecule. In DFNB, the C−Cl stretching vibrations appeared at 800(vw)cm–1 in FT-Raman spectrum. The C−Cl in-plane bending vibrations were found at 630(vw) and610(vw) cm–1 in FT-Raman spectrum.4.1.4. Nitro group vibrationsAromatic nitro compounds have strong absorptions due to asymmetric and symmetricstretching vibrations of the nitro group at 1570–1485 and 1370–1320 cm–1, respectively,Hydrogen bonding has a little effect on the nitro group asymmetric stretching vibrations. Thestrong and very weak bands at 1800 cm–1 and 1600 cm–1 have been assigned to asymmetric andsymmetric stretching modes of nitro group. Aromatic nitro compounds have a band of weak tomedium intensity in the region 590–500 cm–1 due to the out-of-plane bending deformations modeof nitro group. This is observed at 500 cm–1 in FT-Raman spectrum. The in-plane nitro groupdeformations vibrations have a week to medium absorption in the region 775– 660 cm–1. InDFNB, the nitro group deformation is found within the characteristics region.4.1.5. C‒N vibrationsThe C–N stretching and C–N bending vibrations of a nitro group occur near 870 and 610cm–1, respectively. The bands are assigned to C–N stretching vibration of a nitro group forDFNB have been found at 1060(m) and 970(m) cm–1. The C–N out-of-plane bending vibrationsare occurred within the characteristics region. From these observations it is found that thestretching bond; C–N is influenced by other modes. After scaling down, the computed value forC–N stretching vibration by B3LYP/6-31+G(d,p) methods nearly coincide with observed valuesof FT-IR and FT-Raman and these assignments are in good agreement with literature data.ConclusionThe vibrational frequencies of the fundamental modes of the DFNB have been preciselyassigned and analyzed and the theoretical results were compared with the experimentalvibrations The observed and calculated fundamental frequencies B3LYP method using6-31+G(d,p) basis set shows similar profiles in both position and intensities making normal modeassignments with confidence. The assignments made were compared with the experimentalvalues.References[1] V. Suryanarayana, A. Pavan Kumar, G. Ramana Rao, G.C. Pandey, Spectrochim. Acta48A (1992) 1481.[2] V. Krishnakumar, N. Jayamani, R. Mathammal, J. Raman Spectros. 40 (2009) 936.[3] P. Muralidhar Rao, G. Ramana Rao, J. Raman Spectros. 20 (1989) 529.[4] J. Clarkson, W. Ewen Smith, J. Mol. Struct. 655 (2003) 413.[5] D.K. Singh, S.K. Srivastava, B.P. Asthana, Vib. Spectros, 56 (2011) 26.[6] M.J. Frisch, A.B. Nielsen, A.J. Holder, Gaussview user’s manual, Gaussian Inc.,Pittsburgh, PA, 2009.[7] A.D. Becke, J. Chem. Phys. 98 (1993) 5648.[8] C. Lee, W. Yang, R.C. Parr, Phys. Rev. B 37 (1998) 785.[9] P. Pulay, G. Fogarasi, G. Pongor, J.E. Boggs, A. Vargha, J. Am. Chem. Soc. 105 (1983)7037.[10] G. Fogarasi, P. Pulay, in: Durig J. R. (Ed.) Vibrational Spectra and Structure, Vol.14,Elsevier, Amsterdam, Chapter 3, 1985,125.[11] T. Sundius, Vib. Spectrosc. 29 (2002) 89.[12] MOLVIB (V.7.0):Calculation of Harmonic Force Fields and Vibrational Modes ofMolecules, QCPE Program No. 807,2002.[13] D.C. Young, Computational Chemistry: A Practical guide for applying Techniques toReal world Problems (Electronic), John Wiley and Sons Inc., New York, 2001.[14] N. Sundaraganesan, S. IIlakiamani, H. Saleem, P.M. Wojciechowski, D. Michalska,Spectrochim. Acta 61A (2005) 2995.[15] G. Keresztury, J.M. Chalmers, P.R. Griffiths (Eds.), Raman Spectroscopy: Theory inHand Book of Vibrational Spectroscopy, John Wiley & Sons Ltd., New York, 2002;[16] G. Keresztury, S. Holly, G. Besenyei, J. Varga, A.Y. Wang, J.R. Durig, Spectrochim.Acta A, 49 (1993) 2007.[17] M. Karabacak, D. Karagoz, M. Kurt, Spectrochim. Acta 61A (2009) 2995.[18] N. Sundaraganesan, S. Kalaichelvan, C. Meganathan, B. Dominic Joshua, J. Cornard,Spectrochim. Acta 71A (2008) 898.

VIBRATIONAL INVESTIGATION, MOLECULAR STRUCTURE OF 1 , 2 DI CHLORO - 4 - FLUORO - 5 NITRO BENZENE

https://jconsortium.com/index.php/scholar/article/view/72/50

VIBRATIONAL INVESTIGATION, MOLECULAR STRUCTURE OF 1 , 2 DI CHLORO - 4 - FLUORO - 5 NITRO BENZENE

Abstract

Similar works

Full text

Available Versions

Scholar