Photochemistry solution

The photochemistry of carbonyl compounds has been extensively studied, both in solution and in the gas phase. It is not surprising that there are major differences between the photochemical reactions in the two phases. In the gas phase, the energy transferred by excitation cannot be lost rapidly by collision, whereas in the liquid phase the excess energy is rapidly transferred to the solvent or to other components of the solution. Solution photochemistry will be emphasized here, since both mechanistic study and preparative applications of organic reactions usually involve solution processes. 

The solution photochemistry of these complexes has been studied extensively (44.45). The photoproducts observed in solution are species like Co4(CO)12 and Co2(CO)g. These photoproducts are consistent with a mechanism involving declustrification of the Co C core. 

The photocycloaddition of an aldehyde or ketone with an olefin to yield an oxetane was reported by Paterno and Chieffi in 1909. 58> Contemporary studies on the synthetic utility and mechanistic features were initiated nearly 50 years later by Biichi et al. 59) Two review articles summarizing synthetic aspects of Paterno-Biichi reactions have been published 6.12)) and mechanistic studies have been reviewed several times. 6,38,60-62) The reaction involves the addition to olefin of a photo-excited carbonyl moiety. This circumstance makes it advantageous to review this reaction before a discussion of olefin-olefin additions, because the solution photochemistry of carbonyl compounds is probably better understood than any other aspect of organic photochemistry. Many of the reactions of carbonyl compounds have been elucidated during studies of the important phenomena of energy transfer and photosensitization. 63-65)... 

MILLER ETAL. Potysilanes Solution Photochemistry Lithography... 

In solution photochemistry in the presence of acids, the primary process is also the same except that both NND and the aminyl radical are protonated the recombination of the aminium radical and NO to give 295A is too slow to compete with bond scissions174 (Scheme 11). The failure of oxygen to quench nitrosamine photoreactions in either solution (see below) or gas phases under various conditions must also mean a very short lifetime of singlet excited nitrosamines, in agreement with the fast dissociation159,160. 

Addison, J.B., Silk, P.J., and Unger, I. The photochemical reactions of carbamates II. The solution photochemistry of matacil (4-dimethylamino-m-tolyl-Wmethyl carbamate) andlandrin (3,4,5-trimethylphenyl-Wmethylcarbamate), BuU. Environ. Contam. Toxicol, ll(3) 250-255, 1974. 

Sakamoto et al. also reported the solution photochemistry for la-d, which gave the corresponding thietane-fused -lactams 2a-d as shown in Table 2 [30,31]. For tigloyl derivatives Ic and Id, P-lactams were obtained as a mixture of two stereoisomers (entries 6 and 8). The anti isomers were preferably formed, in ratios of 0.8 and 0.7, respectively. In the solid-state photoreaction of... 

In contrast to the solution photochemistry, irradiation of the crystals of le provided remarkably high diastereoselectivities in the formation of 2e. The temperature at which the reaction occurs is important in determining dia-stereoselectivity. At 15 °C, the de of syn-2e was 61 % and the ratio of syn/anti was 8.7, which was the reverse of that in the solution reaction (syn/anti=0.9). The solid-state photoreaction proceeded even at -78 °C, and with higher diastereo-selectivity. At low conversion (9%), only syn isomers (de=93%) were obtained, and 71% de was observed even at 90% conversion. 

Precambrian solution photochemistry, inverse segregation, and banded iron formations. Nature, 276, 808-9. 

Interest in the reprocessing of spent nuclear fuels has prompted studies of the solution photochemistries of Np and Pu. A recent review summarizes the photoredox behavior of the various oxidation states of these elements.169... 

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