Spectral LFER studies on some sydnone chalcones

. A series containing ten ( E )-4-( N -(4-cinnamoylphenyl)sulfamoyl)-3-( p -tolyl)-1,2,3-oxadiazol-3-ium-5-olates were prepared and examined their purities by literature method. The infrared and NMR spectral data were assigned and correlated with Hammett substituent constants and Swain-Lupton’s constants using single and multi-regression analysis. From the results of statistical analyses the effects of substituents on the spectral data have been discussed.


INTRODUCTION
Sydnones are five membered mesoionic dipolar compounds [1]. With reactivity and stability they are fairly different compounds from other aromatics [2]. Sydnones plays on important role in medicinal, heterocyclic and theoretical chemistry [3]. These compounds used as key intermediates for synthesis of organic compounds and possess physiological potentials. They possess many biological activities such as antimicrobial [4], antiviral [5], anti-tumour [6], analgesic [7], anti-inflammatory [8], anthelmintic [9], free-radical scavenging[10, nitric oxide donor [11] and anti-cancer [12]. Sydnone chalcones also possess these properties. Spectroscopic data were useful for prediction of geometry and ground state equilibration of organic compounds [13]. From vibrational spectra the s-cis and s-trans conformations of carbonyl compounds were predicted [14]. The chemical shifts of NMR spectra were useful for prediction of geometry of compounds such as E or Z along with coupling constants [15]. Proton chemical shifts splitting patterns used for prediction of spatial arrangement of heterocyclic ring protons in cyclohexane and five membered pyrazolines [16]. Correlation analysis was used for studying reaction speeds, structural conformations of alkenes [17], alkynes [18], α,β-unsaturated aldehydes [19], ketones [20], ω-substituted ketones [21] and its esters, halo acyl bromides [22], 1 H pyrazoles [23] and its derivatives. Thirunarayanan and Manikandan have studied the dosage of drug analysis using correlation study [ 24]. Thirunarayanan et al., have studied the infrared and NMR spectral correlations of phenazine and quinoxaline derivatives [21,22]. Mayavel et al.,have studied the spectral correlation of some E-imines [23]. The Qsar and Qpr spectral correlation of some dihyroisoxazoles were reported by Thirunarayanan and Sathiyendiran [25]. Thirunarayanan and his co-workers have studied the effect of substituents on spectral data of some oxazine-2-amines [26]. The spectral correlation of infrared and carbon-13 NMR data of quinoxaline and phenazine derivatives were studied by Thirunaryanan et al. [27,28]. Senbagam et al., have studied the effects of substituents on some substituted (E)-N-benzylidene-4H-1,2,4-triazol-4-amines [29]. Vijayakumar et al., have investigated the spectral correlation analysis on some (E)-2-benzylidenehydrazine carbothioamides [30]. The effect of substituents on some hydrazine derivatives were investigated by Rajarajan et al., [31]. On the complete literature survey, the similar study was not reported with sydnone based chalcones. Hence, the authors have reported first time and taken efforts for the study of spectral correlation of the titled compounds by IR and NMR spectra.

General
In this present investigations, chemicals used were purchased from Sigma-Aldrich Company Bangalore, India. Infrared spectra (KBr, 4000-400 cm −1 ) were recorded on a Briker (Thermo Nicolet) Fourier transform spectrophotometer. The NMR spectra of all pyrazolines were recorded on a Bruker AV400 spectrometer operating at 400 MHz to record 1H and 100 MHz for 13C spectra in CDCl 3 solvent with TMS as internal standard.

ILCPA Volume 53
The correlation of deformation modes of CH ip (ν, cm −1 ) of the synthesised sydnone chalcones gave satisfactory correlations with Hammett σ, σ + , σ I constants and F parameters excluding H, 2-OCH 3 and 4-CH 3 substituents. The resonance components of the substituents were fail in correlation.
The correlation of deformation modes of CH op (ν, cm −1 ) of the synthesised sydnone chalcones gave satisfactory correlations with Hammett σ, σ + , σ I constants and F parameters excluding 4-F and 4-OH substituents. Also here the resonance components of the substituents were fail in correlation.
The correlation of deformation modes of CH=CH op (ν, cm −1 ) of the synthesised sydnone chalcones gave satisfactory correlations with Hammett σ, σ + , σ R constants and R parameters excluding 4-NO 2 substituent. The inductive and field components of the substituents were fail in correlation.
The correlation of deformation modes of C=C op (ν, cm −1 ) of the synthesised sydnone chalcones gave satisfactory correlations with Hammett σ, σ + , σ R constants and R parameters excluding H, 4-F, 4-OH and 2-OCH 3 substituents. The inductive and field components of the substituents were fail in correlation.
The NH stretches (ν, cm −1 ) of chalcones gave satisfactory correlation with Hammett substituent constants and R parameters excluding 4-F and 4-CH 3 substituents. Here, the field components of the substituents were fail in correlation.
The poor correlations obtained for the SO 2 stretches (ν, cm −1 ) of chalcones with Hammett substituent constants, F and R parameters.
A satisfactory correlation was obtained for CO syd (ν, cm −1 ) of chalcones with Hammett substituent constants and R parameters. The field effect of the substituents were fail for production of correlation. The reason for failure in correlation was already stated and along with resonanceconjugation structure as illustrated in Fig. 2.
A satisfactory correlation was obtained for H β chemical shifts (ppm) with Hammett σ, σ + , σ R constants and R parameters. The inductive and field components of the substituents were fail in correlations.
The Hammett σ I constant and F parameters gave satisfactory correlation with the chemical shifts(ppm) of NH protons of the synthesised sydnone chalcones excluding 3-Br substituent. The Hammett σ, σ + , σ R constants and R parameters gave poor correlations with NH proton chemical shifts(ppm) of sydnone chalcones, The Hammett substituent constants, F and R parameters were fail in correlation for the methyl proton chemical shifts(ppm) of sydnone chalcones. The reason for the failure in correlation was already stated in earlier and associated with resonance-conjugated structure as shown in Fig. 2. In proton chemical shift correlations, all single regressions gave positive ρ values. This means that the normal substituent effect operates in all system.

13 C NMR spectral study
The 13 C NMR spectral chemical shifts(ppm) of synthesised sydnone chalcones are presented and Table 5. These data are correlated with Hammett substituent constants, F and R parameters using single and multi-linear regression analysis [13][14][15][16]. The results of single parameter correlation analysis of 13 C NMR spectral chemical shifts(ppm) of synthesised sydnone chalcones are tabulated in Table 6. From Table 6, the correlation of δCO(ppm) of the chalcones gave satisfactory correlation coefficients with Hammett σ + , σ I constants and F parameters. The remaining Hammett σ, σ R constants and R parameters fail in correlations. This is due to the inability of substituents effects already stated and associated with conjugative structure as shown in Fig. 2. Table 5. The 13 C NMR chemical shifts (δ, ppm) of (E)-4-(N-(4-cinnamoylphenyl)sulfamoyl)-3-(ptolyl)-1,2,3-oxadiazol-3-ium-5-olates.
A satisfactory correlation coefficients obtained for the correlation of Ar-C-C β carbon chemical shifts(ppm) of sydnone chalcones with Hammett σ, σ + , σ R constants, F and R parameters. The Hammett σ I constant was fail in correlations.
The correlation of Ar-C-CO carbon chemical shifts(ppm) of sydnone chalcones with Hammett σ, σ + , σ R constants and R parameters produced satisfactory correlation coefficients. The Hammett σ I constant and F parameters were fail in correlations.

CONCLUSIONS
About ten (E)-4-(N-(4-cinnamoylphenyl)sulfamoyl)-3-(p-tolyl)-1,2,3-oxadiazol-3-ium-5olates were prepared and examined their purities by literature method. The infrared and NMR spectral data were assigned and correlated with Hammett substituent constants and Swain-Lupton's constants using single and multi-regression analysis. From the results of statistical analyses, most of the single parameter correlations gave satisfactory correlation coefficients. All regression produced positive ρ values. This positive value inferred that the normal substituent effect operates International Letters of Chemistry, Physics and Astronomy Vol. 53 51 in all systems. The multi-regression analysis gave satisfactory correlation coefficients in all spectral data. In these correlations the probability factor was more than 90%. This implies that the degree of correlations was more than 90% feasible.