Ethylene photolysis sensitized

Irradiation of ethyleneimine (341,342) with light of short wavelength ia the gas phase has been carried out direcdy and with sensitization (343—349). Photolysis products found were hydrogen, nitrogen, ethylene, ammonium, saturated hydrocarbons (methane, ethane, propane, / -butane), and the dimer of the ethyleneimino radical. The nature and the amount of the reaction products is highly dependent on the conditions used. For example, the photoproducts identified ia a fast flow photoreactor iacluded hydrocyanic acid and acetonitrile (345), ia addition to those found ia a steady state system. The reaction of hydrogen radicals with ethyleneimine results ia the formation of hydrocyanic acid ia addition to methane (350). Important processes ia the photolysis of ethyleneimine are nitrene extmsion and homolysis of the N—H bond, as suggested and simulated by ab initio SCF calculations (351). The occurrence of ethyleneimine as an iatermediate ia the photolytic formation of hydrocyanic acid from acetylene and ammonia ia the atmosphere of the planet Jupiter has been postulated (352), but is disputed (353). 

In the analogous studies of the photolysis of sulfolane (31), the work of Honda and coworkers66 was carried out in the gas phase at 70-130 °C and established the formation of S02, ethylene, cyclobutane and acetylene as the major products, on mercury-sensitized photolysis. In considerable contrast, photolysis of sulfolane at 185 nm in the liquid phase67 produced ethylene( = 0.22), the sultine (32) (parallel experiments on aqueous solutions of sulfolane, a sulfinic acid is also believed to be formed. The authors believe that both four-membered (33) and six-membered (32) sultines may be formed during these photolyses. Further work in this area would appear to be necessary to unravel the full mechanistic details. 

Photochemistry. The Hg(3P,) sensitized photolysis ofC2H2 has produced benzene, hydrogen, and polymer [Shida et al. (872)]. Since the Hg(3Fi) state does not have sufficient energy required to dissociate the H—C2H bond, the products must be produced by reactions of an electronically excited C2H2. The photolysis of acetylene at 1849 A has produced hydrogen, ethylene, vinylacetylene, diacetylene, benzene, and solid polymers [Tsukada and Shida (979), Zelikoff and Aschenbrand (1082)]. 

Preliminary studies (6) have shown that the ratio of ethylene to carbon monoxide is a function of the temperature as well as the wavelength. This ratio is a measure of the relative importance of reaction (24) as compared to (25) and (26). The ratio of cyclopropane to propylene which measures the relative rates of (25) to (26) is independent of temperature and pressure at 3130 A. and has a value of 15.5. In photolysis at 2537 A., the same ratio is 2 and besides is found to be sensitive to the total pressure. The geometry of the system lias also been found to be a factor. 

Porter and Spear have reported the mass spectrum of aziridine 8 ) which shows HC=NH+ as the base peak in addition to peaks which correspond to (M—1)+, (M—2)+ and CH3. The mercury sensitized photolysis of aziridine 8 ) gives predominantly ethylene and nitrene. This heteroatom effect does not apply to the mass spectral photochemical correlation for ethylene oxide, which shows very similar behavior in both systems.82)... 

Thietanes are photochemically unstable and should be protected from light if they are to be stored for any length of time. Short-lived (hot) biradical intermediates, for example, 98a, appear to be formed and can undergo a variety of reactions, as shown for thietane. " Mercury-sensitized photolysis gives triplet biradicals that are longer lived than the singlet biradicals formed on direct excita-tion. " Some cyclopropane product is produced in the sensitized photolysis. The second excited singlet state of thietane decomposes either to ethylene and thio-formaldehyde via a 1,4-biradical or to elemental sulfur and cyclopropane. ... 

It seems that, under the conditions studied, the ethylene elimination occurs from the triplet state, and that free radicals are formed from both the excited singlet and the triplet molecules. The results, however, clearly indicate the importance of the extent of vibrational excitation in determining the mode of decomposition. (Note the different conclusions regarding the states responsible for primary process I in the direct and acetone-sensitized photolysis.) Since the vibrational levels involved in the two cases may differ considerably, we suggest this dissimilarity as a possible explanation for the different characteristics shown by the direct... 

On photolysis of 1 in the presence of alkenes or open-chain and cyclic 1,3-dienes, the generated di-/-butylsilylene participates in a [1+2] cycloaddition to furnish siliranes. In the cases of cyclopentene 4, cyclohexene 5 and the monosubstituted ethylenes 6 and 7, the respective siliranes 8-11 were obtained as air-sensitive, colorless oils in good to very good yields [3, 4]. This behavior is... 

The Hg-sensitized photolysis of several ethers in the liquid phase was briefly studied by Tsao (264). The gas phase photosensitized decomposition of ethers has found much more interest. In Steacie s group before 1950 there were investigated diethyl ether (265), ethylene oxide (266), and dimethyl ether (267). Cvetanovic and co-workers studied ethylene oxide (268) and trans-2,3-epoxybutane (269). Subsequent work on dimethyl ether was done by Pottle et al. (259), Takezaki et al. (270), Loucks and Laidler (271), and Payette et al. (252). The Hg-sensitized... 

In summary, we have demonstrated that photolysis/fluores-cence chemical kinetics techniques must exploit ongoing advances in laser technology. A highly-sensitive, quasi-cw, ultraviolet laser source was constructed and used in definitive chemical kinetics experiments. OH-ethylene reactions have been characterized in terms of OH addition and hydrogen atom abstraction channels, and questions have been raised concerning both the importance of the addition process and the accuracy of presently recommended kinetic parameters for the abstraction process at combustion temperatures. 

A soln. of 1,6-bis(dimethylamino)pyrene as sensitizer, startg. N-acoxyphthalimide (prepared from 4-(p-rerr-butylphenyl)butanoic acid and N-hydroxyphthalimide using dicyclohexylcarbodiimide), and r rr-butyl mercaptan (2%) as H-donor in 95 5 isopropanol/water under argon irradiated with a 100 W high-pressure Hg-lamp through a filter (> 350 nm) for 2 h - product. Y 88% (by GC). cf. Synth. Meth. 39, 78. With this sensitized photolysis, reaction may be performed in a wide band of visible light (350-450 nm). F.e. and conditions, also ethylene derivs. from p-sulfonylcarboxylic acids, s. K. Okada et al., J. Am. Chem. Soc. 110, 8736-8 (1988). 

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