Hydrogen, Deuterium

Mass spectrometry has been used to determine the amount of H2 in complex gas mixtures (247), including those resulting from hydrocarbon pyrolysis (68). Mass spectrometry can also be used to measure hydrogen as water from hydrocarbon combustion (224,248). Moreover, this technique is also excellent for determining the deuterium hydrogen ratio in a sample (249,250). 

Hypoxanthine, 7-ethyl-synthesis, 5, 584 Hypoxanthine, 1-methyl-deuterium-hydrogen exchange, 5, 527 synthesis, 5, 594 Hypoxanthine, 2-methyl-methylation, 5, 532 synthesis, 5, 587 Hypoxanthine, 3-methyl-free radical methylation, 5, 544 irradiation, 5, 543 synthesis, 5, 584 Hypoxanthine, 8-methyl-synthesis, 5, 584 Hypoxanthine, 9-methyl-methylation, 5, 532... 

Purine, 6-iodo-alkylation, 5, 530 synthesis, 5, 563, 597 Purine, 6-iodo-9- -D-(2,3,5-tri-0-acetyl)ribofuranosyl-synthesis, 5, 598 Purine, 9-isopropyl-deuterium-hydrogen exchange, 5, 527 Purine, 9-(2,3-0-isopropylidene-/3-D-ribofuranosyl)-6-methoxy-synthesis, 5, 584 Purine, 6-mercapto-biological activity, 5, 604 metabolism, 1, 237 as pharmaceutical, 1, 159 tautomerism, 5, 509 Purine, 2-methoxy-synthesis, 5, 596 Purine, 6-methoxy-irradiation, 5, 543 riboside... 

Tetrazole, 5-phenoxy-l -phenyl-mass spectra, 5, 801 photolysis, 5, 811 Tetrazole, 1-phenyl-deuterium-hydrogen exchange, 5, 806 mercuration, 5, 59 NMR, 5, 798 tautomerism, 5, 804 UV spectra, 5, 798 Tetrazole, 2-phenyl-NMR, 5, 798 tautomerism, 5, 804 UV spectra, 5, 798 Tetrazole, 5-phenyl-alkylation, 5, 818 anti-inflammatory activity, 5, 835 blowing agent, 1, 410 reactions... 

Xanthine, 8-ethyl-synthesis, 5, 574 Xanthine, 9-hydroxy-8-methyl-synthesis, S, 596 Xanthine, 1-methyl-deuterium-hydrogen exchange, S, 527 methylation, S, 533 occurrence, S, 598 reduction, 5, 541 synthesis, S, 589 Xanthine, 3-methyl-deuterium-hydrogen exchange, S, 528 methylation, S, 533 reduction, S, 541 synthesis, S, 595 Xanthine, 7-methyl-deuterium-hydrogen exchange alkylation, S, 527 reduction, S, 541 synthesis, S, 587 Xanthine, 8-methyl-synthesis, S, 574 Xanthine, 9-methyl-methylation, S, 533 nitration, 5, 538... 

Using a selected ion flow tube (SIFT) technique, DePuy and coworkers studied such rates of deuterium-hydrogen exchange for a series of neutral carbon acids10. Table 1 contains some selected rates of exchange with DO- from DePuy s work these rates are approximate measures of relative acidity in the gas phase. 

Studies in deuterated water have shown that the hydroxyl proton does not end up in the ethanal formed. The decomposition of the 2-hydroxyethyl is not a simple P-elimination to palladium hydride and vinyl alcohol, which then isomerises to ethanal. Instead, the four protons stemming from ethene are all present in the initial ethanal product [6] (measured at 5 °C in order to suppress deuterium/hydrogen exchange in the product) and most authors have therefore accepted an intramolecular hydride shift as the key-step of the mechanism (see Figure 15.2). There remains some doubt as to how the hydride shift takes place. 

Examples 28 and 29 are for deuterium-hydrogen exchange reactions. The reaction in Example 28 was carried out at a temperature low enough so that the only reaction after adsorption was that of CgHj (ads) with D (ads), followed by desorption. Sarkany, Guczi, and Tetenyi (54) suggested for their reaction that the rate-determining step was cyclohexane adsorption. The log L values indicate that dissociative adsorption of cyclohexane (Step 2, cyclohexane), for which log L = 19, is possible. But some surface freedom of cyclohexane is required. Dissociative adsorption of D2, for which log L = 15, seems more likely. 

Scheme 15.4 Deuterium/hydrogen (D/H) exchange reaction in ionic liquids promoted by lr(0) nanoparticles.

As already reported in Section II,A, the amination of 6-bromo-5-deuterio-4-phenylpyrimidine with potassium amide in liquid ammonia provides a produet in which deuterium is no longer present. Based on the work deseribed previously, it seems reasonable to conclude that this easily occurring deuterium-hydrogen exchange takes place in the intermediary imidoyl bromide (17a, X = Br) (Scheme 11.18) and not in the cyanoazadiene (17b). In the strong basie medium a fast equilibrium can be formulated between these open-ehain intermediates (17a, X = Br, 29, and 30) (Scheme 11.18). 

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