STRUCTURE OF 2 1,3,5-SUBSTITUTED 2-PYRAZOLINES, C20H18N2O5 AND C20H20N2O5

The structures of methyl methoxycarbon-ylphenyl)-2-pyrazoline-3-carbox ylate (1) and methyl methoxycarbonylphen-yl)-2-pyrazoline-3-carboxylat e (2a) are compared. In (1), there is an extensive conjugation involvi ng the N-N=C chain of the pyrazoline ring and the phenyl and carboxy g roups bonded at NI and C3, respectively. In (2a), the presence of a st rong hydrogen bond between the hydroxyl group and the methoxycarbonylp henyl group causes the rotation of the latter with respect to the pyra zoline ring by 47-degrees, with a partial loss of conjugation and with the elongation of the N1-phenyl bond.