Migration of hydrogen from

These may be described either as a type of Si-M cleavage reaction or as a migration of hydrogen from metal to silicon. Clearly they represent the reverse process to the well-known oxidative addition reaction discussed in Section II, F. 

The isolation of a vinylcyclopropane in the reaction of 33 (equation 102) indicates that the reaction involves two stages. TTie first is cleavage of a side bond, which may later be followed by cleavage of the central one The process involves a migration of hydrogen from C(4) to C(3). When C(4) is substituted by two methyl groups as in 84, 85 is obtained... 

In contrast to keto-enol tautomerism, such enol-enol tautomerism is characterized by extremely rapid hydrogen transfers. It was shown by ab initio calculations that structures 32a and 32b are more stable than the degenerate tautomeric forms 32c and 32e by 104.7 kJ mol as well as by 117 kl mol than symmetric structure 32d. According to these calculations, a synchronous tunneling of two protons must occur in the naphthazarine molecule 32 between the identical structures 32a and 32b with a frequency of 20 to 40 MHz, i.e. approximately 10" to 10" migrations of hydrogen from one oxygen atom to another per second take place. 

An alternative approach by Zhu et al. (1990) yielded a similar activation energy (for P), while providing new information on the donor-hydrogen dissociation reaction. With electrical measurements they studied the electric-field induced migration of hydrogen that is thermally released from PH... 

The migration of hydrogen through an allyl system is rearrangement of order 1, 3 because the univalent hydrogen move from C-l to C-3. 

Enols form by tautomerism from the keto form by migration of hydrogen atom from the adjacent carbon atom to the carbonyl group (Ref 1)... 

The linear dimers 89-91 are formed by Ni [32], Co [33], Fe [34] and Pd [35] catalysts. Linear dimers 90 and 91 are produced via the formation of metal M—H, accompanying migration of hydrogen. The formation of 89 is discussed later. The mechanism of the formation of 91 was studied by an experiment using butadiene 92 deuterated at the terminal carbons. In the formation of the branched dimer 91 from the deuterated butadiene 92, catalysed by Co or Fe complexes, insertion of the second butadiene occurs at the substituted side of the 7r-allyl complex 93 to give 94. Finally, the triene 96 is formed from 95 and Fe—H(D) is regenerated. 

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