Isatin 3-semicarbazone and 1-methylisatin 3-semicarbazone.

The two title semicarbazones, namely 2,3-dihydro-1H-indole-2,3-dione 3-semicarbazone, C9H8N4O2, (I), and 1-methyl-2,3-dihydro-1H-indole-2,3-dione 3-semicarbazone, C10H10N4O2, (II), show the same configuration, viz. Z around the imine C=N bond and E around the C(O)-NH2 bond, stabilized by two intramolecular hydrogen bonds. The presence of a methyl group on the isatin N atom determines the difference in the packing; in (I), the molecules are linked into chains which lie in the crystallographic (102) plane and run perpendicular to the b axis, while in (II), the molecules are arranged to form helices running parallel to a crystallographic screw axis in the a direction.