MOLECULAR STRUCTURES OF SOME CHLORALIDES AND A STUDY OF P[PI]-D[PI] BONDING IN SOME ORGANOGERMANIUM COMPOUNDS

Abstract

The crystal and molecular structures of 1-lactic acid chloralide and 1-malic acid chloralide have been determined by X-ray diffraction methods. L-lactic acid chloralide crystallizes in the monoclinic space group, p21, a= 7.650 (3), b = 5.856 (2), c = 9.808 (4) Å, ?= 99.64 (3)° , Z = 2. L-malic acid chloralide crystallizes in the monoclinic space group, p21, a= 10.456 (2), b = 5.818 (10), c = 16. 638 (3) Å, ? = 94.76 (2)° , Z= 4. The five-membered ring system of these compounds is slightly twisted out-of-plane. The CCl3 group is trans to the CCH3 group in 1-lactic acid chloralide and to the CH2COOH group in the 1-malic acid chloralide. The IR spectra of 1-malic acid chloralide and d-malic acid chloralide are discussed in relation to the structures of these compounds. The chemical shifts of the protons on the C-5 position in the compounds are about 4.83 ppm in 1-lactic acid chloralide, 4.89 ppm in 1-malic acid chloralide and d-malic acid chloralide, respectively: These values show that the configurations of these compounds are trans-substitutions. The long-range coupling constant ( J1r = 1.37 to 1.68 Hz ) between the cross-ring protons (on C-2 and C-5) in five membered ring structure of chloralides confirms that the conformations of the compounds are trans-forms (in cis-forms, J1r = 1.1 Hz). The geminal coupling between two protons on the methylene (-CH2COOH) of the malic acid chloralides may be the result of intramolecular hydrogen bonding which hinders the C-C bond between CH(ring) and CH2COOH from rotating freely and causing the two protons on the CH2COOH group to have different chemical environment. The IR spectra of di-lactic acid chloralide, 1-lactic acid chloralide, d-malic acid chloralide and 1-malic acid chloralide are discussed in relation to the structures of these compounds.