On the photodimerization

Table 10.3. Solvent and Concentration Effects on the Photodimerization of Acenaphthylene<41)...

In the category of more elaborate calculations are an SCF—PMO treatment of the reaction of cyclopentadiene with cyclopropene 33>, and calculations including overlap on the photodimerization of linear steroidal dienones. 31> A very fine, detailed theoretical study of thymine photodimerization has been recently presented. 47> Other PMO calculations on photocycloadditions of biochemical interest have also been published. 48>49>... 

Recent studies on the photodimerization of olefinic crystals several examples, which deviate from accepted topochemical principles, have been... 

Effect of Solute-solute Clustering on the Photodimerization of Cyclohexenone... 

Nagata, C., A. Lmamura, Y. Tagashira, andM. Kodama Quantum mechanical study on the photodimerization of aromatic molecules. J. Theoret. Biol. 9, 357 (1965). 

The CASPT2 results on the photodimerization of two cytosine molecules taking place along the triplet manifold are compiled in Figure 16-14. As can be deduced from this figure that the MEP computations from 3(LE) lead directly to the triplet step-wise intermediate 3(SWI) with out any energy barrier. This intermediate (3(SWI)) is characterized by the formation of a single covalent bond... 

Among the numerous examples of organic solid state photopolymerizations (e.g., 9-12) only two systems have been thoroughly studied with regard to the relationship between crystal and molecular structure. The first is the so called four-center type photopolymerization (Reaction 1) which was investigated by Hasegawa and co-workers (13) this is a straightforward translation of the work of G. M. J. Schmidt (3) and his students on the photodimerization of cinnamic acids in the crystalline state into polymer chemistry. 

Photodimerization reactions involving aromatic rings of two naphthalene units are not as frequently encountered as those involving anthracene. A study of the effect of high pressure on the photodimerization of methyl 3-methoxy-naphthalene-2-carboxylate shows that the rate can be doubled (at 2000 bars), but this represents a much lower activation volume than for similar thermal reactions. An intramolecular dimer is formed when the a f/-[3.3]-(l,4)naphthalenophane (182) is irradiated the cycloadduct reverts to (182) on heating or on further irradiation. The syn isomer of (182) does not undergo this reaction. 

Recently, the effects of flexible and rigid caps introduced to the primary rim of y-CD (50a-d, 57a-c) on the photodimerization of AC were investigated, as capping is known to significantly modify the binding and reaction behavior of native CDs. " The chemical... 

ABSTRACT. The photodimerization of 2-anthracenesulfonate in water was accelerated in the presence of 3- and y-cyclodextrins (CyDs). While four configurational isomers of the photodimer were obtained in the presence of Y-CyD with similar ratio of the yields to that in the host-free solution, only one of the isomers was obtained in the presence of 3-CyD. The results were explained by the formation of two guest-one host inclusion complex in the former case and of two guest-two host inclusion complex in the latter. No evidence of an inclusion complex with a-CyD was obtained. The inclusion effects of CyD on the photodimerization of other water-soluble anthracenes were also examined. 

The inclusion effect of CyDs on the photodimerization of 2AC was quite similar to that in the 2AS/CyDs system. 9AC showed no complexation with CyDs and the photoreaction of this compound was little affected. 

Early works on this approach concerned the preparation of photocurable polymers based on the photodimerization observed in maleimides and mono- and disubstituted maleimides [231-233], as depicted in Scheme (44). 

Aqueous medium containing micelles have a great influence on the photodimerization of 3-n-butylcyclopentenone (106) and isophorone (109) (Scheme 5.35). Reversed orientations in aqueous micellar medium, with respect to organic solvent, were also observed in the photodimerization of 2-substituted naphthalenes, 2-pyridones ° (a [4 + 4] cycloaddition), and in the photocycloaddition reaction of 1-heptenylacetate with 3-n-butyl-cyclopenten-2-one (106) (Scheme 5.36). 

The first systematic study concerning the relationship between the chemical reactivity of an organic solid and its crystal structure is generally associated with the work of Schmidt and his co-workers on the photodimerization of cinnamic acid and its derivatives. The main conclusions were summarized by Schmidt in 1971 and phrases such as topochemistry and crystal engineering were set to enter the lexicon of the organic solid state chemist. ... 

Koser, G.F. and Liu, V.-S., Heavy-atom effect on the photodimerization of acenaphthylene substituent analysis on the efficiency of external aromatic perturbers, /. Org. Chem., 43, 478,1978. Muszkat, K.A. and Sharafi-Ozeri, S., Electronic overlap population as reactivity measure. The photodimerization of acenaphthylene, Chem. Phys. Lett., 38, 346, 1976. 

Kato, T. and Nakamura, Y., MiceUar ahgnment effect on the photodimerization of 2-pyridones, Heterocycles, 16,135,1981. 

Intensive studies concerning topochemical reactions have been reported on the photodimerization of cinnamic acid and its derivatives. Schmidt and co-workers proposed a geometrical criterion for the photodimerization in the crystalline state that the reacting double bonds should be situated within about 4.2 A of each other and aligned parallel. In the case of the photoactive single crystal of 1-n-octylthymine obtained from acetonitrile solution (Form III), however, the distance between the reacting double bonds of the thymine bases was 4.47 A. It is difficult to apply Schmidt s rule to the photodimerization of the 1-n-octylthymine crystals. Therefore, it is necessary to determine the feature within the crystal of 1-n-octylthymine for the photodimerization reaction in the crystaUine state. 

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