Scrambling of hydrogen

These two experiments indicate that extensive scrambling of hydrogen between the hydride and PMe2Ph ligands occurs upon... 

A further piece of evidence to elucidate the catalytic pathway of silylformylation was provided by a pair of deuterium-labeled reactions. The results revealed that the scrambling of hydrogen atoms between a hydrosilane and a terminal acetylene is minimal during the reaction and that the hydrogen atom of the formyl group and the vinylic hydrogen are derived from the hydrosilane and the acetylenic proton, respectively (Eq. 8) [15 bj. 

Isomerization reactions of benzene that result in scrambling of hydrogen and carbon atoms presumably involve a benzvalene intermediate and thermal or photochemical rearomatization depending on which of the CC bonds indicated in Scheme 37 by a heavy or a broken line is cleaved, either the rearranged product is formed or the reactant is recovered (Wilzbach et al., 1968). 

An alternative explanation for the scrambling of hydrogen involves an intermolecular exchange. Although this possibility cannot be eliminated, the decomposition of tetramethyl-l,l,l-d3-ammonium methoxide in methanol solution led to a mixture of deuterated ethers which was similar to that observed in the dry salt. If an intermolecular exchange was occurring, more of the deuterium should have been incorporated into the solvent rather than equilibrating between ammonium ions. 

The photochemistry of indene and several alkylindenes in solution and in the gas phase, using deuterated substrates, however, reveals extensive intramolecular scrambling of hydrogen and carbon in the five-menibered ring by multiple hydrogen and alkyl migrations27. 

The reaction was clearly intramolecular since no scrambling of hydrogen and deuterium between molecules was observed below 1050°C. 

Structure 3 has C2V symmetry and corresponds to protonation of methane along an HCH bisector. At the MP4(SDQ)/6-311G(d,p)//MP2/6-31G(d) level of theory, 3 is l.lkcalmol" above It has two pairs of equivalent hydrogens and the closeness in energies of 1 and 3 indicates that the barrier for scrambling of hydrogens in is very low. 

The dimethylplatinum(ll) complex with a bidentate iV,iV,iV -trimethyl-A -(2-picolyl)ethylenediamine ligand undergoes methylation by Mel and protonation by several protic acids to produce cationic trimethylplatinum(iv) complex 1018 and methylplatinum(ll) complex 1019, respectively (Scheme 129). The protonation involves an intermediate cationic hydrido(dimethyl)platinum(lv) complex 1020. Scrambling of hydrogen atoms between hydride and methyl ligands during the reaction indicates an intermediate complex with methane as a ligand. 

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