Photochemistry alkanes

Yin G Z and Nicol M 1985 Photochemistry of naphthalene in alcohol or alkane solutions at high pressures J. Phys. Chem. 89 1171... 

Class TJ, Casida JE, Ruzo LO (1989) Photochemistry of etofenprox and three related pyrethroids with ether, alkane, and alkene central linkage. J Agric Food Chem 37 216-222... 

Ozin GA, Flugues F, Mattar SM, McIntosh DF (1983) Low nuclearity silver clusters in faujasite-type zeolites optical spectroscopy, photochemistry and relationship to the photodimerization of alkanes. J Phys Chem 87 3445-3450... 

Photochemistry and Radiation Chemistry of Liquid Alkanes Formation and Decay of Low-Energy Excited States... 

Most publications dealing with the photodecomposition of alkanes discuss the processes in the gas phase several comprehensive works have already been published in this field [14-17]. In the present work, we summarize the results of liquid phase photolytic studies and compare them with those obtained in radiolysis. An early review on liquid alkane photochemistry was published in Ref. 18, a brief overview of the field was given in Ref. 19. 

It would be elegant to finish the part on photophysics and photochemistry of liquid alkanes by giving a picture that unifies the temperature- and energy-dependence results obtained in fluorescence and photodecomposition studies. However, the spectroscopic information available for alkane molecules is not sufficient to identify the exact excited states involved in the radiative and nonradiative processes [55]. Because of the lack of information, there are different views on the positions and identities of excited states involved [52,55,83,121,122]. 

Because of such difficulties as the featureless absorption and emission spectra in the vacuum ultraviolet region, very weak and energy-dependent fluorescence intensity, short excited-state lifetime, etc. the photophysics and photochemistry of alkanes is much less known than those of other organic molecules, for instance, aromatic hydrocarbons. In this chapter, the present status was reviewed. 

Foldiak, G. Wojnarovits, L. Photochemistry of liquid alkanes, in Proceedingd of Baxendale memorial symposium, Centro Stampa Lo Scarabeo Bologna, 1983 21 pp. 

Wang, S. W., P. G. Georgopoulos, G. Li, and H. Rabitz, Condensing Complex Atmospheric Chemistry Mechanisms. 1. The Direct Constrained Approximate Lumping (DCAL) Method Applied to Alkane Photochemistry, Environ. Sci. Technol, 32, 2018-2024 (1998). 

An extraordinary variety of reactions of organic compounds are known to occur under the influence of visible and ultraviolet light. Some of these, such as the photochemical halogenation of alkanes and photosynthesis in green plants, already have been discussed (see Sections 4-4D and 20-9). It is notour purpose here to review organic photochemistry in detail — rather, we shall mention a few types of important photochemical reactions and show how these can be explained by the principles discussed in the preceding section. 

Table 6, entry 48) whereas alkene isomerization is very slow [52]. Photochemistry is also used in the rhodium-catalyzed alkylborylation of alkanes in which boroalk-anes (Table4, entry 49) are obtained [53], An example of a gas-phase reaction is the photochemical mercury-catalyzed hydroxymethylation of cyclohexane to hydroxymethylenecyclohexane (Table 6, entry 50). This reaction is an example of the abstraction of a hydrogen atom from an alkane by an excited metal atom [54]. 

In the photochemistry of larger molecules the same physical principles apply and the sequence of events is essentially the same, although descriptions are more complex and less precise. Opposite to diatomic, the polyatomic molecules can yield a multitude of different sets of products. To establish the photodissociation mechanism, the nature of the elementary chemical process undergone by an electronically excited molecular entity (primary photoreaction) yielding primary photoproducts should be known, eg in the case of alkanes both the radical fission... 

In polar solvents (pyridine, THF, alcohols, etc.) the photochemistry of simple M-M bonded systems seems to be different based on the products observed (14, 15). For example, irradiation of Mn2(CO)io can give Mn(C0)s . But this chemistry very likely originates from the 17-valence radical as the primary product. Disproportionation of the 17-valence electron species, perhaps after substitution at the radical stage, can account for the apparent heterolytic cleavage. If the excited state reaction is truly dissociative, as the evidence from cross-coupling in alkane suggests, there should be little or no influence from solvent. 

Oxidative addition of H2, alkanes, and silanes to electron-deficient metal species has attracted considerable attention. A continuum exists between nonclassical, or a, complexes such as r] -U2 or the solvated alkane complexes described above and the classical, or fully oxidatively added, species such as dihydrides. Photochemistry represents a major, and in many cases only, source of the reactive intermediates central to this chemistry. As such, detailed studies have been conducted of the reactions of photointermediates with these reagents in a variety of media and phases. The chemistry of dihydrogen and a bonded complexes has been extensively reviewed by Heinekey and Oldham, " Sweany, and Kubas. ... 

DUiydride photochemistry is not limited to reductive elimination. CpRe(PPh3)2H2 is known to photochemically catalyze H/D exchange between CeDe and other arenes or alkanes. Photochemical studies of the mechanism of this process have ruled out loss of phosphines and instead postulate photochemical transfer of one or both hydrides to the cyclopentadienyl ligand yielding a 14-e intermediate, ( -C5H7)Re(PPh3)2, as a hkely intermediate. ... 

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