Deuterium exchange during hydrogenation

This is analogous with the classic chemical reaction in which hydrogen and deuterium exchange during a collision ... 

Treatment of isogarryfoline (59) with 10% DC1 in D20 gave (60). The n.m.r. spectra of (60) revealed deuterium substitution at C-16 and C-17. The mechanism outlined in Scheme 2 accounts for this observation and explains the stereochemistry observed i.e., D+ is transferred from the less-hindered exo side during ketonization. When (60) was treated with dilute HC1, no deuterium exchange by hydrogen was observed in 24 hours. However, after 96 hours, (61) was obtained. This result further supports an enol-ketone mechanism. 

T. F. Narbeshuber, M. Stockenhuber, A. Brait, K. Seshan, J. A. Lercher, Hydrogen/deuterium exchange during-butane conversion on H-ZSM-5, J. Catal, 1996, 160, 183-189. 

Deuteriums in the enolizable positions of a,/3-unsaturated keto substrates are unaffected during the course of the reduction. This extends the applicability of this procedure to the preparation of y-labeled ketones by subjecting the substrates to hydrogen-deuterium exchange (section ll-C) prior to reduction. This technique has been utilized for the preparation of the y-labeled ketones (156), (157) and (158). " The deuteriums in the a-positions of these ketones are back exchanged (section 11-B) after the reduction. 

An alternative mechanism for double bond migration has recently been proposed by Smith (Fig. 2.12).113 It is based in part on theoretical calculations,114 in part on the recent surface science work suggesting that hydrogen occupies threefold hollows,115 and in part on the experimental observation that during hydrogenation an allylic deuterium moves 1-3 across the bottom of an adsorbed allylic system without being exchanged.116... 

The purpose of this experiment was to investigate the extent and the structural specificity of hydrogen exchange during the extraction of bituminous coal with naphthalene. Table I includes the data of an extraction experiment (E20) conducted with naphtha-lene-d8 using nitrogen as the cover gas. In the experiment, the reactants were heated at 380°C for 1 hour at 2200 psi the same apparatus was applied as in E19. After the run, the spent solvent was separated from the coal by distillation, and the coal and solvent were examined for deuterium and protium incorporation. 

The exchange of neopentane with deuterium has been examined over a number of metal films by Kemball ( ) and over nickel films at higher temperatures by Rowlinson et al. (29). This compound has attracted interest because an a-P multiple exchange process cannot operate, and an process is necessary if more than three hydrogen atoms are to be exchanged during a single sojourn of the molecule on the catalyst. 

Low pressures (10 6 torr) of a reagent gas may be introduced during the delay between ion formation and excitation to provide more selective Cl reactions, such as hydrogen/deuterium exchange reactions (18) or to provide a source of low energy electrons for electron capture negative ion Cl reactions (53, 54). As in the case of "self-CI", the extent of these Cl reactions may be controlled by changing the delay time between ion formation and excitation. 

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