Aminopyrazoles and their conjugated acids. An X-ray study of 3,5-dimethyl-4-aminopyrazole and the Picrate of 3(5)-aminopyrazole

✍ Scribed by Lourdes Infantes; Concepción Foces-Foces; Rosa María Claramunt; Concepción López; José Eiguero

• Publisher: Journal of Heterocyclic Chemistry
• Year: 1999
• Tongue: English
• Weight: 366 KB
• Volume: 36
• Category: Article
• ISSN: 0022-152X
• DOI: 10.1002/jhet.5570360303

✦ Synopsis

Abstract

The crystal structure determination of 3,5‐dimethyl‐4‐aminopyrazole (3) and of 3(5)‐aminopyrazolium picrate salt (5a) have been undertaken. The packing in 3 is characterized by the formation of sheets in which the N‐H of the pyrazole and one H atom of the amino group are involved. The remaining HB donor interconnects sheets. In 5a, the anions and the cations are linked by a two‐dimensional network of hydrogen bonds in the ab plane. Each N‐H and C‐H in the cation are involved in hydrogen interactions with the O atoms of the anion. Ab initio molecular orbital methods at the HF and B3LYP levels using a 6–31G** basis set have been carried out to compare the relative stability of the tautomeric forms of the 3(5)‐aminopyrazolium and 4‐aminopyrazolium cations.