Reactions photochemical in solid

Photochemical reactions in solid polymers were studied to find that MV2+ is reduced photochemically by carbohydrates in their solid phase 45) (Scheme 4). 

While photochemical reactions in solids are somewhat counterintuitive and relatively rare in organic synthesis, recent examples have suggested that reactions in crystals maybe as reliable and efficient as their solution counterparts [57]. As it pertains to the photoelimination of small molecules and C—C bond-forming reactions, it is essential to recognize that product formation relies on the sequential cleavage of two sigma... 

Table 2.5 Factors Controlling Photochemical Reactions in Solids...

The photochemistry of aromatic compounds is classified into the same categories adopted in the previous reviews in the series. The photoisomerization of arylalkenes, photoaddition and cycloaddition to aromatic rings, photosubstitution, photorearrangement reactions have less appeared in the period (2010-2011) considered. On the other hand, the photo-chromism including photoisomerization of azobenzenes and intramolecular photocyclization and cycloreversion of 1,2-diarylethenes, and the photodimerization have been widely developed. Supramolecular Photochemistry as a series of Molecular and Supramolecular Photochemistry was edited by Ramamurthy and Inoue in the period. In addition, it should be noteworthy that so many photochemical reactions in solid and/or crystalline states have appeared and developed. 

It is well recorded that benzopinacol can be obtained quantitatively on photoirradiation of 4,4 -dimethyl benzophenone in isopropylalcohol. However, in the solid state photoirradiation gives the dimeric compound (Scheme 132). Besides the representative example of photochemical reactions in solid phase a large number of illustrations are available. " ... 

Above the glass transition temperature (TJ, the conformational freedom of the polymer chain can be comparable to that in solution, and consequently has equivalent chemical reactivity. However, it is not applicable to all photochemical reactions in solid systems. In the case of epoxy resins, a significant decrease of the glass transition temperature (Tg) has been observed during the photochemical oxidation [216, 220, 728]. 

Thermal and photochemical reactions in the solid state which were studied before 1999 are summarized in reviews [1] and books [2]. 

Toda F (2005) Thermal and Photochemical Reactions in the Solid-State. 254 1-40 Tour JM, see James DK (2005) 257 33-62... 

It would be an advantage to have a detailed understanding of the glass transition in order to get an idea of the structural and dynamic features that are important for photophysical deactivation pathways or solid-state photochemical reactions in molecular glasses. Unfortunately, the formation of a glass is one of the least understood problems in solid-state science. At least three different theories have been developed for a description of the glass transition that we can sketch only briefly in this context the free volume theory, a thermodynamic approach, and the mode coupling theory. 

By chance rather than by design, the third chapter in this volume also emanates from Israel. Bernard S. Green, Rina Arad-Yellin, and Mendel D. Cohen have surveyed organic reactions in the solid state from the standpoint of the stereochemist. In the first part of the chapter, the authors discuss the stereochemical consequences of the crystallization of conformationally mobile systems. Conformational, crystal-field, and hydrogen-bonding effects, among others, are responsible for the selective crystallization of stereoisomers that may not be dominant in solution. The second part of the chapter is concerned with the stereochemical consequences of chemical, and especially photochemical, reactions in the solid state. 

We turn now to a presentation of our own research on the use of built-in or internal chiral auxiliaries for asymmetric induction in photochemical reactions in the crystalline state [28]. This work is a natural outgrowth of the work of Toda and coworkers on the use of external chiral host compounds for the same purpose discussed in Sect. 2.2. In both cases, the primary role of the chiral auxiliary is to guarantee the presence of a chiral space group for the ensuing solid-state photochemical reaction. 

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