The crystal structure of the dimeric acid product of 1-methyl-1,4-dihydronicotinamide

One of the so-called 'acid products' of 1-methyl-l,4-dihydronicotinamide is a crystalline, colorless material with twice the molecular weight of the parent compound. The crystals are monoclinic, space group P21/n, with cell dimensions of a= 13.687, b= 13.488, c= 7.367 A, #= 98 ° 58' and four molecules per unit cell. The structure of the dimer has been determined by a three-dimensional X-ray analysis, using Cu K~ radiation. Phases were initially found for 224 reflections by the symbolic addition procedure and the subsequent refinement was carried out by full-matrix least squares with anisotropic temperature factors to an R of 0.049. Hydrogen atoms were included. The structure