Hydrogen reacting with deuterium molecule

In the aqueous pH region the mechanism for hydrogen-deuterium exchange in pyridine involves attack of deuteroxide ion on the pyridin-ium ion to give an ylide intermediate (Scheme 8). The ylide then reacts with D2O to give the deuterated p30 idine. In more basic media the proposed mechanism involves rate-determining deprotonation from the neutral molecule to give a carbanion intermediate which then abstracts a deuteron from the solvent (Scheme 9). 

It has been observed [23,91,92] that when an unsaturated hydrocarbon is reacted with (a) equilibrated and (b) non-equilibrated hydrogen—deuterium mixtures, the deuteroalkane distributions are identical. Such observations indicate that the direct addition of a hydrogen molecule across the olefinic bond does not occur, and provides strong evidence for the formation of a half-hydrogenated state , that is, an adsorbed alkyl radical, first suggested by Horiuti and Polanyi [81], as a relatively stable reaction intermediate. The process of hydrogenation may thus be represented as... 

The catalytic cycle involving [RuCbCPPhsjs], one of the more active transfer-hydrogenation catalysts, is shown in Scheme 10. The catalyst first forms an alkoxido complex, with elimination of HCl, when allowed to react with the secondary alcohol. This pentacoordinate complex forms an 18-electron species by coordinating a molecule of alkene. The alkoxido ligand transfers its Q -deuterium atom to the metal, after which the ketone oxidation product of the secondary alcohol is eliminated. The steps are believed to occur in... 

Ytterbium atoms have been reacted with thermally generated hydrogen or deuterium atoms, with the resultant formation of YbH and YbD (198). The IR pydh stretching-frequency was observed at 1214.9 cm In addition, Yb atom and YbH absorption and emission spectra were observed. The magnetic parameters of YbH were determined from the esr spectra of the molecules (with Yb nuclear spin 1 = 0 and I = Vi) to be gn = 1.9953, gx = 1.9402, AjCH) = 226 MHz, Ax(H) = 224 MHz, Ax[ Yb (I = Vi)] = 5.266 GHz, A, [ Yb (I = Vi)] = 5.724 GHz. The hyperfine parameters indicated that the spin density is less than 20% on the hydrogen, and that the bonding is largely Yb H. ... 

As mentioned previously, gas-phase H/D exchange reactions are a form of ion/mole-cule reaction in which an analyte ion reacts with a neutral deuterated molecule within the confines of an ion-trap or ion-drift tube. The product of the reaction is a covalent exchange of hydrogen for deuterium in what amounts to a double replacement reaction that is expected to proceed through a stable ion-molecule complex. Like other organic reactions, the extent of gas-phase H/D exchange reactions depends on the number density of molecules of each reactant species present and the time during which they are allowed to react. 

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