An oximino tautomer of 1-n-decyl-4-hydroxyimino-3-methyl-1H-pyrazol-5(4H)-one.

The title compound, C14H25N3O2, consists of a five-membered heterocyclic ring to which a pendant decyl group is attached. The oximino tautomeric character of the mol­ecule is clearly defined by the distribution of well defined double bonds in the heterocycle region (one C=O and two C=N). The most conspicuous packing inter­action is the strong inter­molecular hydrogen bond linking the oximino OH group and the carbonyl O atom to define broad planar hydro­philic strips running along the unique b axis. The alkyl chains adopt a fully extended conformation and lie almost at right angles to these one-dimensional structures, defining their hydro­phobic counterpart.