CALORIMETRIC AND INFRARED STUDY OF METHYL-IODIDE AND SOME MONOSUBSTITUTED BUTYL HALIDES - DOES METHYL-IODIDE FORM HYDROGEN-BONDS AS A PROTON DONOR

The solution enthalpies of methyl iodide, n- and t-butyl chlorides, n- and t-butyl iodides in cyclohexane, carbon tetrachloride, acetone and dimethyl sulfoxide (DMSO) were measured calorimetrically and the tran sfer enthalpies of the solutes from cyclohexane were calculated. The c omparative analysis of the transfer enthalpies shows no remarkable dif ferences that could be attributed to specific interaction between the solvents and the solutes. In addition, the infrared (IR) spectra of th e butyl halides dissolved in CCl4 and deuterated DMSO, and the IR spec tra of methyl iodide in CCl4, deuterated acetonitrile, acetone and DMS O, were investigated. Significant enhancement of the CH3 stretching ba nd intensity was observed for methyl iodide solutions when going from carbon tetrachloride to H-bond-acceptor solvents. This enhancement can be ascribed to the hydrogen bonding of methyl iodide with the solvent s. Meanwhile, no IR spectroscopic evidence of such hydrogen bonding wa s observed when the solutions of n- and t-butyl halides in organic sol vents were considered. A possible reason for the disagreement between the IR and calorimetric measurements is discussed.