Iodine Complexes with Cyclohexanone and Related Compounds¹

Studies were made of the ultraviolet and visible absorption spectra of iodine complexes with cyclohexanone and related compounds in Freon solution. Charge-transfer bands occur at 242 mµ for acetone, 249 mµ for 2-cyclohexenone, 233 mµ for cyclohexanol, and 253 mµ for both cyclopentanone and cyclohexanone complexes. Equilibrium constants, extinction coefficients, and enthalpies for these complexes are given. At higher concentrations of the ketones, a second type of complex with absorption maxima at 300 and 375 mµ dominates the spectra. Since its concentration varies as the square of the first complex concentration, it is thought to be a dimer complex. The dimer complexes have unusually high formation energies of about 20 kcal./mole.