Cryogenic photolysis studies. Part 1.—Iodoalkanes

Abstract

The photolysis of the C1 to C4 iodoalkanes in the solid phase and in argon matrices at 20 K has been investigated by a combination of infra-red spectroscopic examination of the frozen solid, and gas-liquid chromatographic analysis of the final products. The initial photolytic step for iodoethane, the iodopropanes and the iodobutanes leads to production of the alkene-hydrogen iodide complex in dilute matrices, but to a mixture of alkene-hydrogen iodide and iodoalkane-hydrogen iodide complexes in the solid iodoalkane. Secondary photolysis products result from the reaction of hydrogen atoms, produced by the photolysis of hydrogen iodide, with iodoalkane molecules.The photolysis of iodoalkanes in gas, liquid and solid phases, both pure and mixed with inert or reactive diluents, has been extensively in~estigated.~'~ It has been found that the products formed and the kinetics of the photolysis in the gas or liquid states can generally be accounted for satisfactorily by mechanisms involving the initial production of radicals, whereas the comparatively high quantum yields and very wide range of products observed in the solid phase photolysis of iodoalkanes suggest that a different mechanism is operating. Several authors have postulated mechanisms involving the photolysis of aggregates of molecules, rather than of single molec u l e ~. ~" OThe purpose of the present work is to attempt to elucidate the role of molecular aggregates in the solid phase photolysis of the iodoalkanes. We have shown previously that complexes which may be important in such photolyses can be detected by infra-red spectroscopy in low-temperature matrices. Thus we have carried out a study combining spectroscopic examination of the frozen solid phase with gas-liquid chromatographic analysis of the final products.

Matrix Isolation Study of the Photochemically Induced Reaction between Iodoethane and Ozone Trapped in Solid Argon at 16 K. Infrared Spectra of Iodosoethane (C2H5IO), Iodylethane (C2H5IO2), Ethyl Hypoiodide (C2H5OI), Hydrogen Hypoiodide (HOI), Hydrogen Iodide, and Ethanal Complexes

“…Iodosoethane also dissociates to hydrogen hypoiodide and ethene (analogous to photolysis of iodoethane yielding ethene and HI), 27 the subsequent reaction of ethene with oxygen atoms forming ethanal. 28 The yield of ethyl hypoiodide, hydrogen hypoiodide, and ethanal is increased by Pyrex-filtered irradiation.…”

Simulation of the pH Sensing Capability of an Open-Gate GaN-Based Transistor

“…! ) is 59 mV per pH unit (17). Most experimental results show a sensitivity that is slightly less (near 57 mV/pH) (2,16,18).…”

Oxidation of methylene in low-temperature matrices

“…No new absorptions were observed by Barnes et a1. 36 and Ogilvie et after the photolysis of CH,I with either a medium-or low-pressure mercury lamp. However, analysis of the final products by GLC indicated the presence of methane, which earlier studies had shown to be the major product at 77 K. The results were interpreted in terms of C-I bond cleavage followed by simple combination of radicals to reform the parent compound.…”