INTRAMOLECULAR VS INTERMOLECULAR HYDROGEN-BONDING - THE CRYSTAL-STRUCTURE OF 5-METHYL-2-HYDROXYACETOPHENONE THIOSEMICARBAZONE MONOHYDRATE AND SALICYLALDEHYDE-2-METHYLTHIOSEMICARBAZONE MONOHYDRATE

The crystal structure of 5-methyl-acetophenonethiosemicarbazone monohy drate, A, and salicylaldehyde-2-methylthiosemicarbazone monohydrate, B , were determined using single crystal X-ray diffraction. A crystalliz es in the monoclinic space group C2/c, with lattice parameters a = 14. 161(2), b = 15.753(1) Angstrom, c = 11.084(1) Angstrom, beta = 112.59( 1)degrees and Z = 4, yielding a calculated density of D-calc = 1.352 m g/m(3). B crystallizes in the triclinic space group P1, with a = 7.233 (2) Angstrom, b = 7.371(2) Angstrom, c = 11.841(2) Angstrom, alpha = 8 2.77(2)degrees, beta = 78.33(2)degrees, gamma = 63.06(2)degrees and D- calc = 1.371 mg/m(3) for Z = 2,. In both A and B the immine nitrogen a nd the sulfur atom are anti with respect to N2-C8. While A presents th e usual intramolecular six membered hydrogen bond ring, B has instead an intermolecular hydrogen bond between the hydroxy moiety of the sali cyladehyde and a water molecule, AM1 calculations agree with the exper imental conformations observed in both compounds.