THE CONFORMATION AND VIBRATIONAL SPECTRA OF tras-1,4-DIHALOCYCLOHEXANES PART III. trans-1,4-DIIODO-, trans-1,4-BROMOIODO- AND trans-1,4-DIBROMOCYCLOHEXANE

Article abstract of DOI:10.1016/0022-2860(80)80326-7

The IR spectra of trans-1,4-diiodo- and trans-1,4-bromoiodocyclohexane as solutes in various solvents, as pellets and as solids under high pressure are recorded in the region 4000-30 cm^-1.Additional spectra of the melts, amorphous and annealed crystalline solids at 90 K dichloric spectra of oriented crystals are recorded above 200 cm^-1.Raman spectra of the amorphous and annealed solids at 90 K and as solutes in various solvents, are obtained, including polarization measurements.IR and Raman spectra of trans-1,4-dibromocyclohexane in the temperature range 90-250 K are recorded.Equilibrium mixtures of ee and aa conformers of the title compounds are observed in solution, in the melts and in the amorphous solid at 90 K.The ee conformer only is present in the stable crystal, while the aa conformer predominantes in apparently metastable crystals annealed to ca. 205 K.The concentration of the aa conformer increases under high pressure (50 kbar).Fundamental frequencies for both ee and aa conformers are assigned.A normal coordinate analysis is carried out, and the force fields adjusted to nine halogenated cyclohexanes using the overlay technique.