Exchange Reactions of Group III Alkyl Addition Compounds

EXCHANGE REACTIONS OF GROUP III ALKYL ADDITION COMPOUNDS 

As indicated in Sections II and III, it is desirable to have a free monomer for reaction. Thus, we have seen that dissociation of dimers 

For reaction or exchange to occur, either of two paths are possible, as previously discussed for the MegGa amine systems (38). The first of these is described by Eq. (4) for the MegGa-PMeg system (21), in which the activation step is the dissociation of the adduct followed by exchange 

In this reaction there is a preequilibrium step with formation of monomeric MegAl followed by a rate-determining step that is dependent on the monomer concentration and the concentration of complex. The transition state proposed for this is indicated in 13 and involves a 5-coordinate aluminum atom. 

The difference in activation energy between the two processes is small ( a = 16 kcal/mole for the McgGa-PMeg Eg = 14.8 kcal/mole for the MegAl-PMeg with = 21 kcal/mole) with the lower energy for the bimolecular aluminum exchange. 

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Exchange Reactions of Group III Alkyl Addition Compounds. . 118... 

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