Peculiarities of NMR 1Н spectra of 5-arylsulfonyl-1,5-diphenyl-1-penten-3-ones

Abstract

Differential spectral parameters ∆δ n of 5-arylsulfonyl-1,5-diphenyl-1-penten-3-ones have been calculated. Such parameters are the differences between the two basic spectral parameters -δ n values in NMR 1 Н spectra. To analyze the parameters of 1 H NMR spectra, we used the values δ і of the shift of their centers. The displacements of signals of the methylene group CH 2 ∆δ´, the methine group CH ∆δ´´, the protons of the vinyl group ∆δ´´´ and ∆δ´´´´ relative to the unsubstituted 5-arylsulfonyl-1,5-diphenyl-1-pentene-3-one were analyzed. The effect of substituents was evaluated by the parameter Dd і , which was calculated as the difference of chemical shifts of the groups CH 2 , CH and vinyl protons for unsubstituted and substituted arylsulfonyl nuclei. Different correlation constants were used to perform correlation dependences: Hammett constants s p ; s + ;Okamoto-Brown constants s p + and constants s Ф . The maximum difference |Dδ´´| was observed for the methine group CH, much smaller |Dδ´| for the methylene group CH 2 , the smallest values - for |Dδ´´´| and |∆δ´´´´|, which characterize changes in the chemical shifts of vinyl protons. Different correlation constants s were used to perform correlation dependences, but the best correlations were observed for Hammett constants s n ; Okamoto-Brown constant s n + ; s + and constants s Ф . The best correlations with the substituent constants for these 1 H NMR spectra are observed for protons of the CH group, which is directly linked to the arylsulfonyl group. Note that for the CH 2 group an almost perfect correlation was obtained by subtracting the results of the methyl group. An interesting regularity was established that for vinyl protons, more distant from the arylsulfonyl group vinyl protons, obtained good linear correlations for the Hammett constants s п and s + with a high value of R (0.915 and 0.994). It is evident the transmission of electronic influence occurs through the aromatic nucleus and the SO 2 group due to the mesomeric effect, and the sulfonyl group is the active conductor of such influence. The effective usage of differential spectral parameters has been shown using particular spectral task for value of relation influence of atoms and space structure of molecules. Correlation dependences ∆δ–s for chemical shifts of proton signals in 1 H NMR spectra using basic constants s, which take into account resonant interactions, can be successfully used to predict the physicochemical characteristics of 5-arylsulfonyl-1,5-diphenyl-1-penten-3-ones. Keywords : arylsulfones, 1 H NMR spectra, basic and differential spectral parameters, correlation dependences.