Ethyl iodide, photolysis

Koplitz and co-workers have studied the photolysis of C2H5 via the A2A (3s) state by using 248-nm photolysis radiation and hot ethyl radicals generated from photolysis of ethyl halides.125,126 Chen and co-workers have investigated the photodissociation of jet-cooled ethyl (produced by flash pyrolysis of ethyl iodide and n-propylnitrite) in the region of 245-264 nm... 

As mentioned briefly in Chapter 5, the photodimerization of acenaphthylene is subject to a very interesting heavy-atom solvent effect. The results of the photolysis of acenaphthylene in some heavy-atom solvents are given in Table 10.6.<4a) The data in Table 10.6 show that the heavy-atom solvents n-propyl bromide and ethyl iodide yield product ratios similar to that obtained in the sensitized photolysis, indicating a greater role of the triplet state in... 

In order to determine the sensitivity of coumarin dimerization to heavy-atom perturbation, the direct photolysis was carried out in butyl chloride, propyl bromide, and ethyl iodide. Comparison of these results with those obtained in nonpolar solvents indicated that there was no significant change in the amount of the triplet-derived product (80) formed in the heavy-atom solvents as would be expected if heavy-atom perturbation were important.<90) More recent investigations,<93W however, of the formation of (79) in carbon tetrachloride indicate that halocarbon enhancement of the formation of this isomer exists. A direct measure of the intersystem quantum... 

The gas phase photodecomposition of higher alkyl iodides has received relatively little attention and the contribution made by hot alkyl radicals is uncertain. Schindler and Wijnen6 have compared the rate of production of ethane during the photolysis of pure ethyl iodide, with that in the presence of HI and I2. They assume that in the presence of HI, all the ethyl radicals produced in the primary process form ethane, whereas in the presence of I2 ethane is produced only through reaction of hot ethyl radicals with the parent molecule. Since the rate of production of ethane in the presence of HI is approximately fifty times greater than in the presence of I2, they estimate that <2% of the ethyl radicals produced in the primary process react as hot radicals. 

Armed with a strong set of precedents, we applied this photolysis to the reaction of ethyl iodide with N-acylhydrazone 3a (Table 5) [69, 70], Irradiation (300 nm) with Mn2(CO)io using InCl3 as a Lewis acid furnished the ethyl adduct in 85% yield, a dramatic improvement over experiments using triethylborane or hexamethylditin. Control experiments revealed a requirement for both irradiation and Mn2(CO)io on the other hand, the reaction proceeded without InCl3, though sluggishly (21% yield, 2 days). 

A series of other halogenated compounds have been identihed in seawater, including ethyl iodide, propyl iodide, bromoiodomethane, chloro-iodomethane, and di-iodomethane (Carpenter et al., 2000 Klick and Abrahamsson, 1992). Little is known about their production mechanisms. Loss mechanisms are likely to include photolysis and reaction with chloride and hydroxide ions. Information is too limited to be used to derive global fluxes for these compounds, although the data available indicate that a reasonable case can be made that the iodine flux from these compounds is similar to that from CH3I. 

Other photolysis studies have been reported for ethyl iodide -propyl iodide and isopropyl iodide in the gas phase, and also in liquid and solu-tion . Solution and liquid phase studies have also been reported for butyl ° , pentyl and cetyl iodides ". The primary process in the photolysis of alkyl iodides has been further discussed by Donovan and Husain in reference to the formation of excited halogen atoms. 

The first efforts to address this issue involved hydrazone ( ) 62 (Scheme 2.9), prepared as a mixture E/Z 92 8) and separated via flash chromatography as the pure ( ) isomer in 75% yield. In this preparation, the oxazolidinone N amination was accomplished using a solution of monochloramine in methyl tert butyl ether [45], furnishing a quantitative yield of the N amino 2 oxazolidinone, which in turn was condensed with methyl pyruvate to afford 62. Addition of ethyl iodide to ( ) 62 using the Mn mediated photolysis conditions as described above gave 66% yield ofthe ethyl adduct, with a modest diastereomer ratio of 70 30, while the correspond ing isopropyl addition was very effective (85% yield, dr 92 8). Variation in the stoichiometry indicated that amounts less than 2 equiv of Lewis acid proportionally lowered the diastereoselectivity, suggesting that, in this case, the ester may participate... 

The occurrence of this reaction sequence is further substantiated by the observation that adding nitric oxide in the photolysis experiments does not change ethylene-acetylene yields (Table IV). Evidence for the analogous process in ethyl iodide involving elimination of HI has been presented in previous photolysis studies (23, 34). The ethane product observed in the present photolysis study must certainly be formed by the reaction of ethyl radicals which presumably result from another primary dissociation process,... 

Sogoshi, N., Wakabayashi, T., Momose, T., and Shida, T., Infrared spectroscopic studies on photolysis of ethyl iodide in solid parahydrogen, /. Phys. Chem. A, 101, 522, 1997. 

In an attempt to detect alkyl radicals spectroscopically, Thrush168 carried out the flash photolysis of ethyl, propyl, and isopropyl iodides... 

The pure l-ethyl-4-carbomethoxypyridinyl radical 4") was isolated by distillation from the mixture produced by sodimn amalgam reduction of the corresponding pyridinium iodide Flash photolysis of 4 l also yielded the pyridinyl... 

The importance of hot radical reactions in ethyl and higher alkyl iodides is not clear, although there is some evidence of the participation of these reactions during photolysis both in solution and in the gas phase . 

The conversion of berberines into spirobenzylisoquinolines has been examined in detail. As described in section 8 photolysis of the betaines (190, R=H) and (190, R=Me) affords the aziridines (198, R=H) and (198, R=Me). Treatment of (198, R= Me) with methyl iodide is accompanied by Hofmann degradation to give the ochotensine analogue (307, R=Me) and treatment with ethyl chloroformate results in a von Braun degredation... 

The partially fluorinated radicals have been prepared by photolysis of the fluoroalkyl iodides (16, 17) and by the photolysis of the appropriate fluoroalkyl ketone (e. g. CH FCOCH F) (18). Fluorom ethyl and difluorom ethyl radicals have also been formed from the fluoroalkyl iodides using di-Jt-butyl peroxide as initiator (16, 17). Problems can arise in kinetic studies with these radicals because the chain carrying step may involve hydrogen as well as iodine abstraction. In practice this only seems to be of major importance when electronically excited species are present. 

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