Cyclic and acyclic products from the reactions between methyl 3-oxobutanoate and arylhydrazines

The molecules of methyl 3-(2-nitrophenylhydrazono) butanoate, C11H13N3O4, (I), and methyl 3-(2,4-dinitrophenylhydrazono) butanoate, C11H12N4O6, ( II), both prepared from methyl 3- oxobutanoate and the corresponding nitrophenylhydrazine, exhibit polarized molecular electronic structures; in each of ( I) and ( II), the molecules are linked into chains by a single C - H center dot center dot center dot O hydrogen bond. The molecules of 5- hydroxy-3- methyl- 1- phenyl- 1H- pyrazole, C10H10N2O, ( III), prepared by the reaction of methyl 3- oxobutanoate and phenylhydrazine, are linked into chains by a single O - H center dot center dot center dot N hydrogen bond. The reaction between methyl 3- oxobutanoate and 3- nitrophenylhydrazine yields 5- hydroxy- 3- methyl- 1-( 3-nitrophenyl)- 1H- pyrazole, ( IV), which when crystallized from acetone yields 4- isopropylidene- 3- methyl- 1-( 3- nitrophenyl)1H- pyrazol- 5( 4H)- one, C13H13N3O3, ( V).