Group exchange transfer

On the attack of the exchanging metal, a binuclear complex is formed, in which the functional groups are transferred stepwise to the metal ion Mz+. The exchange may also occur by direct reaction of the exchanging metal ion with the protonated (partly unwrapped) complex ... 

Aluminum-alkynyl covalent bonds, characteristics, 9, 249-250 Aluminum-aluminum bonds in A1(I) compounds, 9, 261 in Al(II) compounds, 9, 260 Aluminum aryloxides, reactivity, 9, 254—255 Aluminum(III)ates, in organic group-selective transfers, 9, 279 Aluminum(I)-boron bonds, characteristics, 9, 263 Aluminum(III)-boron exchange, process, 9, 266 Aluminum-calix[4]arene catalyst, for alternating epoxide-CC>2 co-polymerization, 11, 617... 

Figure 9-1- Role of carnitine in fatty acid oxidation. Long-chain fatty acids are activated as the thioester of CoA on the cytoplasmic side of the mitochondrial membrane. The fatty acyl group is then transferred to form the corresponding carnitine ester in a reaction catalyzed by carnitine palmitoyltransferase I (CPT ]) The acylcarnitine then enters the mitochondrial matrix in exchange for carnitine via the carnitine-acylcarnitine translocase. The acyl group is transferred back to CoA in the matrix by carnitine palmitoyltransferase II (CPT II). The intramitochondrial acyl-CoA can then undergo P-oxidation.

The mixed metal compounds,react to form a titanium C complex that is the true catalyst for the polymerization. An alkyl group is transferred from aluminium to titanium in exchange for a chloride. 

The positive inductive effect of a 3-methyl group is transferred to the adjacent 2-position more effectively than that of a 2-methyl to the more remote 5-position. Compared with the rate of a-deuterium exchange for selenophene, itself, the rate is about 0.1 for 5-methyl-2-deuterioselenophene and 0.05 for 3-methyl-2-deuterioselenophene in the presence of strong bases, whereas in acidic media it is about 100 and 1000, respectively.79 The same effect of a methyl group was found... 

Both 1- and 2-alkenyl groups are transferred to Li (see below). When the double bond is more remote from the metal center, reactivity is reduced e.g., 3-butenyl- and 4-pentenyltins do not exchange with n-BuLi in EtjO. 

The effects of introducing halogens in the 2 and 6 position of phenyl imine catalysts was also studied in diimine pyridine iron dichloride/MAO systems [13]. These catalysts afford linear products with a low olefin content, generally less than one (olefin) functionality per chain. The latter is due to a fast transfer of iron bound alkyl groups to the aluminum compounds that are present in excess. After hydrolysis, alkanes are obtained. When a high ratio of aluminum alkyl to iron catalyst is used, polyethene waxes are obtained due to the statistically favored alkyl group exchange between the metal species. 

The extra stability of vinyl Grignard reagents is clearly shown by Knochel s preparation of 22 by exchange with i-Pr2Mg. Notice that the alkenyl group is transferred rather than the alkyl group to benzaldehyde and that both metallation and reaction with the aldehyde occur with retention of configuration.2... 

After completion of the first sequence, carboxybiotin moves to the second site, where the carboxyl group is transferred from biotin to pyruvate, forming oxal-oacetate. In essence, a proton and a carboxyl group trade places in this step. Isotope effects indicate that proton removal from pyruvate is not concerted with carboxylation (60, 61). The lack of positional isotope exchange (62) during this process presumably is because the active complex is isolated from solvent, rather than because of a lack of exchangeable sites. 

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