Conformational Analysis of a New Analgesic Triazolinethione

Crystals of 3-(2-hydroxyphenyl)-4-methyl-1,2,4-Δ-2-triazoline-5-thione, a new non-narcotic analgesic compound, are monoclinic with the following cell parameters: a = 5.942, b = 17.771, c = 10.319 à , β = 102.77°, Z = 4, space group P 2 1/ C . The structure was determined by the direct-phasing program MULTAN and by Fourier methods. The triazoline ring makes an angle of 62° with the benzene ring, and this result has been compared with the dihedral angle value between the pyrazolone and phenyl planes of antipyrine derivatives. A theoretical calculation of conformational energy is also reported and structure-activity relationships are discussed.