Ultraviolet photolysis, carbon monoxide

No information was found on the transformation of diisopropyl methylphosphonate in the atmosphere. Based on the results of environmental fate studies of diisopropyl methylphosphonate in distilled water and natural water, photolysis (either direct or indirect) is not important in the transformation of diisopropyl methylphosphonate in aquatic systems (Spanggord et al. 1979). The ultraviolet and infrared laser-induced photodegradation of diisopropyl methylphosphonate in both the vapor or liquid phase has been demonstrated (Radziemski 1981). Light hydrocarbon gases were the principal decomposition products. Hydrogen, carbon monoxide (CO), carbon dioxide (C02), and water were also detected. 

Carbon Suboxide Photoiysis. In principle, carbon suboxide (1) can be used as a precursor to atomic carbon and two molecules of carbon monoxide as shown in Eq. 2. However, this reaction is endothermic by 141 kcal/mol and can only be realized in the vacuum ultraviolet (UV) at wavelengths that destroy most organic substrates. However, photolysis of 1 at 1470 A produces C atoms in a low-temperature matrix. The short wavelength flash photolysis of 1 coupled with atomic absorption has been used to measure the rate constants for various spin states of carbon with simple substrates. 

Biacetyl. Photolysis of biacetyl was first reported in 1923 by Porter, Ramsperger, and Steel 121> who initiated the vapor at 100° and identified the products as ethane and carbon monoxide. Subsequently methane, acetone, ketene, and 2,3-pentanedione were also recognized as products. Considerable effort has been expended to achieve a full understanding of the details of the primary processes and progress was reviewed by Noyes, Porter and Jolley 113> in 1956. Irradiations have been performed over a wide range of pressure, temperature and wavelength (including the far ultraviolet 68> and mercury photosensitization 69>). Overall and individual quantum yields varied widely. 

Ultraviolet photolysis of carbon monoxide occurs through absorption in narrow lines, corresponding to specific rotational and vibrational levels of several electronic transitions. The absorption wavelengths are isotope-dependent due to the effect of isotopic mass on the vibrational and rotational energies. As a consequence, the absorption lines due to C 0, the most abundant isotopologue, do not overlap those due to C O and Because of the... 

Analogous decarbonylations have been observed for ketones under ultraviolet irradiation at elevated temperatures. From a preparative point of view the behavior of diphenyl-substituted and a,a-divinyl-substituted ketones is interesting, as they are decarbonylated when their benzene solutions are subjected to ultraviolet irradiation.69 This favorable effect of phenyl sub-stitutents on decarbonylation has been noted also for cyclic ketones for example, under suitable conditions l-phenyl-2-indanone eliminates carbon monoxide and yields 90% of 5,6,ll,12-tetrahydro-5,6-diphenyldibenzo[a,e]-cyclooctene as a mixture of cis- and trans-forms,10 whereas 2-indanone itself is hardly decarbonylated at all in benzene solution. That in other cases decarbonylation is usually more profitable in the gas than in the liquid phase is shown by studies of the photolysis of tetramethyl-l,3-cyclobutanedione which in the gas phase gives 2 equivalents of carbon monoxide and a quantitative yield of 2,3-dimethyl-2-butene.71... 

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