CRYSTAL-STRUCTURES, MOLECULAR-CONFORMATIONS, HYDROGEN-BONDS, AND CL-35 NQR IN SOME CHLORAL HEMIACETALS

Crystal structures of chloral 4-bromo-, 4-methyl-, 2,4-dichlorobenzylh emiacetals, and iso-butylhemiacetal were determined by the single crys tal X-ray method at room temperature. Two modifications were found for the 2,4-dichlorobenzyl derivative. A chiral chain of molecules formed by OH...O hydrogen bonds (H-bonds) along a 2(1) axis is common to the crystals studied, except for iso-butyl derivative where a centrosymme tric dimer is formed by H-bonds. Conformation analyses were made using molecular mechanics. The crystal structures and IR spectra indicated that the H-bonds in these crystals except for the 2,4-dichlorobenzyl d erivate were bifurcated ones. An intramolecular OH...Cl interaction wa s found in the iso-butyl derivative. The relationship between the Cl-3 5 NQR spectrum and the molecular structure are discussed.