Ketone cage effects

TABLE 4 Cage Effects for Singlet and Triplet Benzyl Radical Pairs Produced from Dibenzyl Ketones and Benzyl Phenylacetates on Silica at 20°C (see Scheme 8) [121, 122 ... 

Figure 12 Cage effect during the photolysis of dibenzyl ketone. Top GC traces of products in micelles and solution. Bottom Cage effect with respect to the detergent concentration. Note the sudden change in the cage effect at the cmc.

Figure 13 Variation of cage effect during the photolysis of dibenzyl ketone with respect to detergent chain length.

Figure 3 shows the effect of applied magnetic field on the cage effect for 1 and some of Its Isotopic Isomers. The higher cage effect for enriched ketone (compound 8 in Figure 3) cor-... 

Asymmetrically substituted dibenzyl ketones (ACOB) have been employed frequently as precursors of geminal triplet radical pairs in studies of cage effects in constrained or microphase-compartmentalized media. ... 

Fig. 4. The cage effect for benzyl- 1-methylbenzyl ketone a function of concentration of the surfactant HDTC1 shows a typical CMC profile...

Alcock and Whittle had previously reported on a similar reaction involving CF3 and CH3 radicals, but Pritchard and Bryant ° > ° showed that the related reaction between CF2H radicals was of little importance during the photolysis of 1,1,3,3-tetrafluoroacetone. Robb et alP have discussed the cage effect in the liquid-phase photolysis of fluorinated ketones. 

Due to the cage effect in micelles, unsymmetrically substituted dibenzyl ketones such as 13 yield predominantly the unsymmetrical diphenyl-ethanes on photodecurbonylation, whereas in homogeneous solution all three possible products are formed in the statistical ratio 1 2 1 (Turro and Kraeutler, 1978). 

With butyric acid, fast deactivation occurs, except for zeolites belonging to the erionite-offiretite family, on which selective ketonization to 4-heptanone is possible [2]. This has been attributed to the presence of the so-called erionite cage and the occurrence of a cage effect, comparable to that obtained with alkanes [2]. Based on this knowledge, the selective formation of certain ketones has been attempted using mixtures of short chain carboxylic acids. 

Another clear example of the cage effect introdnced when MOFs are used as nanoreactors was reported by Pan et al. [34]. These anthors stndied the use of the MOF [Co3(4,4 -BPhDC)3(4,4 -BPY)] (4,4 -BPhDC = biphenyl-4,4 -dicarboxylate, L ) as host for photochemical reactions, using o-methyl dibenzyl ketone (o-MeDBK) as a probe (see Scheme 10.2). 

The photochemical decomposition of asymmetrically snbstituted dibenzyl ketones in confined spaces (snch as zeolites), and the analysis of the prodnct distribution can serve to determine the cage effect and the mobility of the free... 

---