it can be shown by means of detailed 1h- and 13c-nmr studies of both isomers and some other structurally related compounds that the nitro group in nitrefazole is in position 4 of the imidazole ring , whereas the other pharmacologically active nitroimidazoles like metronidazole are mainly substituted in position 5 ( or in exceptional cases in position 2 ) .
C0028179
nitroimidazoles
C0025872
metronidazole