The crystal and molecular structure of pyrazole

Abstract

The space group of pyrazole is P21en with eight molecules in the unit cell. There are two crystallographically independent molecules and good agreement is obtained for the lengths of corresponding bonds. The bond lengths of the molecule indicate that there is a large contribution from the betaine form to the resonance hybrid. The molecules are hydrogen-bonded together in a figure-8 spiral, these helices forming a dose-packed array in the crystal.