Naphthalene, hydrogenation exchange with deuterium

The a-position in naphthalene (and other condensed polycyclic aromatics) is sterically hindered. Hodges and Garnett have shown, for example, that at 100°C and in the presence of Pt(II)-salts the /1-hydrogen exchanges with deuterium 28 times faster than the a-hydrogen (55). This could suggest that Pt-catalyzed direct C6-cyclization will also favor the /3-position. 

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. 

Hydrogen addition and exchange reactions between a bituminous coal and a donor solvent or a nondonor solvent were investigated using fully-deutrated Tetralin and naphthalene. In the experiments conducted with coal, Tetralin-di2 and deuterium at 400°C, the ratio of hydrogen exchange to addition was on the average 2.0. 

The spent naphthalene-hs was examined by XH NMR for structural changes in the solvent. No hydrogenation of the naphthalene was detected. The naphthalene-ds was examined to determine the amount of deuterium which was exchanged with protium in the coal. After 10 h, 21.1% of the deuteriun in the a and e positions of naphthalene had exchanged. The a position was the most active position for exchange. 

Hydrogen donors labelled with deuterium, such as tetralin-and naphthalene-4 have also been used to study the reaction mechanism of the hydrogen transfer. Tetralin-(ii2 is rapidly substituted in the 1-position by hydrogen from coal. At a reaction temperature of 400 °C the deuterium content of the 1-position remains, after a reaction time of 15 min, relatively constant at 66%. The 2-position, however, participates much less in the exchange reaction. On the other hand, the deu-... 

Hydrogen-deuterium exchange in diazoalkanes, 53, 43 HYDROGENOLYSIS OF CARBON-HALO-GEN BONDS WITH CHROMIUM (II)-EN PERCHLORATE NAPHTHALENE FROM 1—BROMONAPHTHALENE, 52, 62... 

These clusters are stabilized by the formation of surface complexes with naphthalene. The hydrogen-deuterium exchange in hydrocarbon, RH, takes place... 

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