Photochemical Reactions of Carbonyl Compounds

This simple model allows us to rationalize the major t) es of reactions that are characteristic of carbonyl compounds reacting from an n,n excited state  

The orbital model of formaldehyde on page 791 provides a simple basis for discussing the photochemical reactions of carbonyl compounds. For a more detailed discussion of the excited states of formaldehyde and acetaldehyde, see Hadad, C. M. Foresman, J. B. Wiberg, K. B. /. Phys. Chem. 1993, 97,4293. 

For another analysis of the photochemistry of carbonyl compounds, see Formosinho, S. J. Arnaut, L. G. Adv. Photochem. 1991, 16, 67. 

These reactions are characteristic of nonconjugated carbonyl compounds other reactions (page 841) may be observed when conjugated carbonyl systems are photoexcited. 

Jorgensen, W. L. Salem, L. The Organic Chemist s Book of Orbitals Academic Press New York, 1973 p.84. 

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Photochemical reactions of carbonyl compounds with alkenes give the oxetanes (Scheme 30). The stereochanical course depends on the substituents of the alkenes [16]. The reactions proceed with the retention of the configuration of the alkenes for the electron accepting substituent, e.g., CN. The stereochemical integrity is lost for the donating group, e.g., OCH. ... 

Explain the role of the photochemical reactions of carbonyl compounds in the photoinitiated polymerisation of vinyl monomers and cross-linking in polymers. 

A common photochemical reaction of carbonyl compounds is the transfer of a hydrogen atom to the carbonyl oxygen atom ... 

The photochemical reaction of carbonyl compounds and alkenes, which is referred to as the Paterno-Buchi (PB) reaction, was developed in 1909 [13], and is currently one of the most widely used methods for oxetane synthesis (Scheme 7.4). As exemplified in the PB reaction of benzophenone with 2-methylpropene [14], a selective formation of the oxetane is possible even when the photochemical reaction involves highly unstable molecules that is, the excited state of carbonyls. Due to its synthetic importance and mechanistic interest, the PB reaction is the most extensively studied synthetic method for oxetanes. Thus, several extensive reviews describing the PB reaction have been published since 1968, and the reader is directed towards these for further information [15]. In this chapter, methods that allow for the control of the regioselective and stereoselective formation of synthetically important oxetanes will be described. 

Yang, N. C. Photochemical reactions of carbonyl compounds in solution. II. Paterno-Buchi reaction and energy transfer. Photochem. Photobiol. 1968, 7, 767-773. 

Nonchain mechanisms, though, often involve radical-radical combinations and disproportionations. Nitroxyls can be used to trap alkyl radicals that may be present in a reaction medium by a radical-radical combination reaction, giving an electron-sufficient species that is more easily studied than the free radical. The photochemical reactions of carbonyl compounds often involve radical-radical combination and disproportionation steps. 

Thermo- and Photochemical Reactions of Carbonyl Compounds in the Solid State... 

Photochemical reactions of carbonyl compounds in solution are often less complex than those in the gas phase because the excess vibrational energy... 

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