Infrared (IR) vCH and CH=CH (cm^_1) out-of-plane stretching frequencies and ¹³C Nuclear Magnetic Resonance (NMR) chemical shifts (ppm) of dCO data were assigned from their respective spectra of a series of various substituted styryl biphenyl, thiophene and 9H-fluorenyl chalcones. These values were correlated with various Hammett substituent constants. From the results of statistical analysis, the effect of substituents on the above frequencies can be explained.

Quantitative structure activity relationship and quantitative property relationship studies deal with the prediction of ground state molecular equilibration (Thirunarayanan, 2007 and Thirunarayanan et al., 2007) of organic substrates such as s-cis and s-trans isomers of alkenes, alkynes, benzoylchlorides, styrenes and a, b-unsaturated ketones from spectral data. Their use in structure parameter correlations has become popular for studying the biological activities (Thirunarayanan, 2008), normal coordinate (Sharma et al., 2002) analysis and transition states of reaction mechanisms (Dass, 2001). Infrared (IR) spectroscopy is a powerful tool technique for the qualitative and quantitative study of natural and synthetic molecules (Griffiths and Chalmers, 2002). IR spectroscopy can provide information about the nature, concentration and structure of samples at the molecular levels (Pellerin and Pelletier, 2005). A great deal of work has been devoted to the reactivity of a, b-carbonyl compounds, particularly, the theoretical study of substituent effects on long-range interactions in the b-sheet structure (Horváth et al., 2005), of oligopeptides and enone-dienol tautomerism (Wang et al., 2005). The other works include the Qsar study of substituted benzo (a) phenazines (Chen et al., 2005) cancer agents, Diels-Alder reactions (Dumont and Chaquin, 2006), density functional theory (Senthilkumar et al., 2006), gas phase reactivity of alkyl allyl sulfides (Izadyar et al., 2006) and rotational barriers in selenomides (Kaur et al., 2006). Delphine et al. (2006) have studied the quantitative structural relationships in a, b-unsaturated carbonyl compounds between the half wave reduction potential, the frontier orbital energy and the Hammett s_p values. Dhami and Stothers (1965) have extensively studied the ¹H Nuclear Magnetic Resonance (NMR) spectra of a large number of acetophenones and styrenes with a view to establish the validity of the additivity of substituent effect in aromatic shielding first observed by Lauterber (1961). Savin et al. (1975) studied the NMR data of unsaturated ketones of the type RC₆H₄-CH=CH-COMe₃ and sought Hammett correlations for the ethylenic protons. Solcaniova et al. (1980) have measured ¹H and ¹³C NMR spectra of substituted styrenes, styryl phenyls and obtained good Hammett correlations for the olefinic protons and carbons. Nowadays, scientists (Sung and Ananthakrishna, 2000; Annapoorna et al., 2002; Lee, 2008; and Thirunarayanan, 2008) are showing more interest in correlating the group frequencies of spectral data with Hammett substituent constants to explain the substituent effects of organic compounds. Recently, Thirunarayanan and Ananthakrishna (2006 a and 2006 b) and Thirunarayanan (2007) investigated elaborately the single and multi-substituent effects on a and b-hydrogen and carbons of some naphthyl chalcones. In the above view, there is no information available in literature for the study of IR deformation modes and ¹³C NMR study of carbonyl carbons with substituted styryl biphenyl, 9H-flurenyl and thiophene ketones. Hence, the authors have obtained the above chalcones by literature method (Thirunarayanan and Vanangamudi, 2006) and assigned the spectral data for vCH, CH = CH deformation out of planes, d ¹³C (ppm) of CO of the chalcones from their respective spectra. The substituent effects of the above data of the compounds are investigated with various Hammett substituent constants.

IR and ¹³C NMR Spectra, Aryl chalcones, Substituent effects, Hammett substituent constants, Correlation analysis, Nuclear Magnetic Resonance, NMR, NMR spectrometer, Deformation frequencies, Systematic investigations, Quantitative structure activity.