INTERMOLECULAR HYDROGEN-BONDED STRUCTURE OF (1R)-(+)-CAMPHOR SEMICARBAZONE

The first crystal structure of a rigid asymmetric semicarbazone, C11H19N3O {hydrazinecarbozamide, (1R)-(+)-1,7,7-methylbicyclo[2.2.1]hept-2-ylene-}, is described. [For a discussion of CAS/IUPAC nomenclature of semicarbazones see Grasselli & Weast (1989). Handbook of Data on Organic Compounds, 2nd ed., Vol. I, Introduction, sectional signs 190, 252. Boca Raton, Florida: CRC Press.] Crystalline (1R)-(+)-camphor semicarbazone (I) was found to have a fused hydrogen-bonded polymeric non-centrosymmetric structure. In each monomeric unit of (I), the hydrazidic H atom and one amidic H atom are syn to the carbonyl O atom; these atoms are involved in the intermolecular hydrogen bonding. The carbonyl O atom of each molecule is hydrogen bonded to the hydrazidic H atom of an adjacent molecule and the syn-amidic H atom of a different adjacent molecule to form a chain of fused eight-membered rings, the conformation of each ring being distorted from planarity. The hydrazidic hydrogen-bond geometry is N-H = 0.83 (4), H...O = 2.31 (4), N...O = 3.137 (4)angstrom and N-H...O = 177 (4)degrees. For the amidic hydrogen bond, N-H = 0.90 (4), H...O = 2.05 (4), N...O = 2.933 (4) angstrom and N-H...O = 167 (4)degrees.