Rearrangement reactions catalyzed

Rearrangement reactions catalyzed by the clay surface were observed for par-athion (an organophosphate pesticide) when it was adsorbed on montmorillonite or kaolinite in the absence of a liquid phase. The rate of rearrangement reactions increased with the polarization of the hydration water of the exchangeable cation (Mingelgrin and Saltzman 1977). Table 14.1 summarizes a series of reactions catalyzed by clay surfaces, as reported in the literature. 

Table 1 Rearrangement Reactions Catalyzed by Coenzyme B12 (AdoCbl)-Dependent Enzymes...

Mechanism of Action. Diol dehydrase is one of the enzymes whose mechanism of action has been studied extensively (13, 14). It has been established that in general the rearrangement reactions catalyzed by adenosylcobalamin-requiring enzymes involve the migration of a hydrogen from one carbon atom of substrate to an adjacent carbon atom in exchange for a group X that moves in the opposite direction. In the case of the diol-dehydrase reaction, X represents a... 

The catabolism of certain amino acids (e.g., valine, isoleucine, methionine) and odd-chain fatty acids (17 0) produces propionyl-CoA. Propionyl-CoA enters the TCA (citric acid) cycle following conversion to succinyl-CoA, as shown in Fig. 28-7. Propionyl-CoA is first carboxylated to produce D-methylmalonyl-CoA, which in turn is then racemized to L-methylmalonyl-CoA. In an intramolecular rearrangement reaction catalyzed by L-methylmalonyl-CoA mutase, a vitamin B12-... 

Table 10 The effect of adding THF to enantioselective rearrangement reactions catalyzed by (97i)...

Figure 22.13. Rearrangement Reaction Catalyzed by Cobalamin Enzymes. The R group can be an amino group, a hydroxyl group, or a substituted carbon.

Davis SM, Zaera F, Somorjai GA (1982) Surface structure and temperature dependence of light-alkane skeletal rearrangement reactions catalyzed over platinum single-crystal surfaces. J Am Chem Soc 104 7453... 

Nakamura, H., Yamamoto, Y. Rearrangement reactions catalyzed by palladium palladium-catalyzed carbon skeletal rearrangements ... 

Figure 22.14 Rearrangement reaction catalyzed by cobalamin enzymes. The R...

The lysine 2,3-aminomutase reaction is reminiscent of the 1,2 rearrangement reactions catalyzed by B -dependent enzymes. The B12 dependence of several enzymic lysine 2,3-aminomutase reactions has been characterized in a variety of animals and microorganisms (222). However, the enzyme from C. subterminale SB4 is apparently not B12 requiring (220), suggesting that the enzymes catalyzing a- to j8-amino transfers are not all evolutionarily related. Given the unique cofactor requirements of the C. subterminale SB4 enzyme, i.e., SAM and Fe(ll), several studies aimed at elucidating the reaction mechanism have recently been reported. 

S.M. Davis, F. Zaera, and G.A. Somoijai. Surface Structure and Temperature Dependence of n-Hexane Skeletal Rearrangement Reactions Catalyzed over Platinum Single Crystal Surfaces Marked Structure Sensitivity of Aromatization. J. Catal. 85 206 (1984). 

Mevalonate is then converted to an isoprenoid unit by a combination of phosphorylation, decarboxylation, and dephosphorylation reactions (Figure 21.28). Three successive reactions, each of which is catalyzed by an enzyme that requires ATP, give rise to isopentenyl pyrophosphate, a five-carbon isoprenoid derivative. Isopentenyl pyrophosphate and dimethylallyl pyrophosphate, another isoprenoid derivative, can be interconverted in a rearrangement reaction catalyzed by the enzyme isopentenyl pyrophosphate isomerase. 

Ortiz de Montellano PR, Nelson SD (2011) Rearrangement reactions catalyzed by cytochrome P450s. Arch Biochem Biophys 507 95 110... 

The 1,2-alkyl/aryl migration reaction is found in various skeletal rearrangement reactions catalyzed by transition metals. See Section 7.2 and Ref. [90] for examples. 

G. Metathese E metathese Olefin m. is a bond rearrangement reaction, catalyzed by transition metal comptounds (molybdenum, tungsten or rhenium) ... 

Octa(phenyl)silsesquioxane is prepared by hydrolysis and condensation of phenyltrichlorosilane and the subsequent rearrangement reaction catalyzed by benzyltrimethylammonium hydroxide [22]. For further derivatization this precursor has to be activated, for example, by halogenation of the phenyl rings. This complex reaction sequence is necessary because halogenated precursors such as bromophenyl silanes of the type X3SiCgH4Br may be readily accessible from Grignard reactions between the benzene derivative and either SiCU or Si(OR)4, but the following hydrolysis and condensation step results in only low yields of... 

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