The far ultra-violet spectra of some branched chain iodo-alkanes, iodo-cyclo-alkanes, fluoro-iodo-alkanes and iodo-alkenes

Abstract

The far-ultra-violet spectra between 30 000 and 90 000 cm^-1 are presented for: 1-iodo-2-methylpropane, 1-iodo-3-methylbutane, 2-iodopropane, iodo-cyclopentane, iodocyclohexane, 2-iodo-2-methylpropane, 1,1,1-trifluoro-2-iodoethane, 1,1,1,2,2,3,3-heptafluoro-3-iodopropane, vinyl iodide, and allyl iodide. Most of the spectra are reasonably similar to those of the 1-iodoalkanes. The existence of axial and equatorial conformers of iodocyclohexane is shown. The substitution of fluorine for some or all of the hydrogens causes a shift to higher energy of the spectra, with the exception of the lowest energy bands. Since the ionization potentials are also shifted to higher energy, the excited σ* level must also be stabilized in the case of the A bands. For vinyl iodide and allyl iodide new bands appear which are tentatively assigned to π* ←n and π* ←π transitions.