STUDIES IN THE AZOLE SERIES. CIV.¹ EXPERIMETAL AND CALCULATED DIPOLE MOMENTS OF 3(5)‐PHENYLPYPRAZOLES

Abstract

The experimental dipole moments of four pyrazoles, namely 3(5)-phenyl-5(3)-methylpyrazole 4, 1,5-dimethyl-3-phenylpyrazole 10, 1,3-dimethyl-5-phenyIpyrazole 11 and 1 -methyl-3,5-diphenylpyrazole 12, were combined with literature data on other pyrazoles (only H, CH3 and C6H5 substituents) to discuss the structure and tautomerism (NH derivatives) of these compounds. Ab initio theoretical calculations, up to 6-31 G**//3-21 G level were carried out to get a deeper insight on their structure, particularly on the conformation of the phenyl groups. The main conclusion is that a phenyl group near the "imine" nitrogen enhances the dipole moment of pyrazoles.