Abstract

A series containing eight 1-phenyl-3(5-bromothiophen-2-yl)-5-(substituted phenyl)-2-pyrazoline derivatives have been synthesized by
microwave assisted, solid acidic green catalyst SiO2-H3PO4 catalyzed cyclization of 5-bromo-2-thienyl chalcones and phenyl hydrazine
hydrochloride under solvent free conditions. The yields of the pyrazolines were more than 85%. The purities of these pyrazolines were
checked by their physical constant, micro analysis, Infrared, Nuclear magnetic resonance and Mass spectroscopic data published earlier in
literature. From the spectral frequencies, infrared (cm-1
) of C=N, C-S, C-Br, 1H and 13C NMR chemical shifts (δ, ppm) of pyrazoline ring
proton, carbon and C=N carbons were assigned and correlated with Hammett substituent constants, F and R parameters. From the results
of statistical analysis the effects of substituent on the spectral frequencies have been discussed.

Key words: 1-phenyl-3(5-bromothiophen-2-yl)-5-(substituted phenyl)-2-pyrazolines; Green synthesis; IR and NMR spectra; Hammett correlations