Structure of a 4-nitroso-5-aminopyrazole and its salts: tautomerism, protonation, and E/Z isomerism.
The structures of 1-benzyl-4-nitroso-5-aminopyrazole (1) and its hydrochloride (1H+) have been determined in the solid state and in solution in DMSO, methanol, and ethanol. The free base exists in solution as a mixture of amino/nitroso tautomers 2a and 2b rather than in the imino/oxime tautomers 3. The conjugated cation 1H+ results from the protonation of the nitroso group. X-ray crystallography showed that both amino hydrogen atoms of 2a form NH...O=N hydrogen bonds: one is intramolecular, the other links adjacent molecules in an infinite chain.
Holschbach
Marcus H
MH
Institut für Nuklearchemie (INC), Forschungszentrum Juelich, D-52425 Juelich, Germany. m.holschbach@fz-juelich.de
Sanz
Dionisia
D
Claramunt
Rosa M
RM
Infantes
Lourdes
L
Motherwell
Sam
S
Raithby
Paul R
PR
Jimeno
María Luisa
ML
Herrero
David
D
Alkorta
Ibon
I
Jagerovic
Nadine
N
Elguero
José
J