Infra-Red Studies of Solvent Effects

Abstract

Two main theories have been put forward to explain the properties, particularly the electronic absorption spectra, of solutions of iodine (or bromine) in various solvents. The most widely held theory^1,2 maintains that 1 : 1 solvent-solute complexes are formed, whereas Bayliss and Rees³ and Bayliss⁴ explain the observed effects in terms of the perturbation introduced by the cage of solvent molecules surrounding each solute molecule. To obtain further information regarding the nature of these solvent effects, we have recorded the vibrational absorption spectra over the range 2.5–25 µ (4,000–400 cm.⁻¹) of solutions of iodine in (a) benzene (1 part) plus carbon tetrachloride (5 parts), (b) ether, (c) pyridine. In each case saturated solutions at room temperature were used.