Exchange reactions of deuterium

The exchange reaction of deuterium with the hydrogens in ammonia is an excellent test for chemisorption of hydrogen Taylor and Jungers9... 

According to Matsusita (46) the. adsorption of ethylene on reduced nickel proceeds in proportion to the 0.44th power of the equilibrium pressure on a sparsely covered surface as shown in Fig. 6. This may indicate dissociative adsorption of the ethylene molecule into two parts although the deviation from the square root type of adsorption (0.5th power) remains unexplained. The absence of the exchange reaction of deuterium... 

Isotopic Exchange Reactions. Exchange reactions between the isotopes of hydrogen are well known and well substantiated. The equihbrium constants for exchange between the various hydrogen molecular species have been documented (18). Kinetics of the radiation-induced exchange reactions of hydrogen, deuterium, and tritium have been critically and authoritatively reviewed (31). The reaction T2 + H2 — 2HT equiUbrates at room temperature even without a catalyst (30). 

J. W. Pyper and C. K. Briggs, Kinetics of the Radiation-induced Exchange Reactions of Hydrogen, Deuterium, and Tritium, Eawrence Eipermore Eaboratory Report... 

In theory two carbanions, (189) and (190), can be formed by deprotonation of 3,5-dimethylisoxazole with a strong base. On the basis of MINDO/2 calculations for these two carbanions, the heat of formation of (189) is calculated to be about 33 kJ moF smaller than that of (190), and the carbanion (189) is thermodynamically more stable than the carbanion (190). The calculation is supported by the deuterium exchange reaction of 3,5-dimethylisoxazole with sodium methoxide in deuterated methanol. The rate of deuterium exchange of the 5-methyl protons is about 280 times faster than that of the 3-methyl protons (AAF = 13.0 kJ moF at room temperature) and its activation energy is about 121 kJ moF These results indicate that the methyl groups of 3,5-dimethylisoxazole are much less reactive than the methyl group of 2-methylpyridine and 2-methylquinoline, whose activation energies under the same reaction conditions were reported to be 105 and 88 kJ moF respectively (79H(12)1343). 

The earliest attempts to prepare deuterated steroids were carried out by exchange reactions of aliphatic hydrogens with deuterium in the presence of a surface catalyst. Cholesterol, for example, has been treated with platinum in a mixture of deuterium oxide and acetic acid-OD, and was found to yield... 

Maybury, C. P., and J. C. Larrabee Kinetics of the Exchange Reaction of Aluminium Borohydride with Deuterium Abstracts of Papers, 135th Meet. Amer. chem. Soc. 1959, 28 M. 

Coillet, D. W., and G. M. Harris Exchange Reactions of Methane and Monodeuteromethane with Atomic Deuterium. J. Amer. chem. Soc. 75, I486 (1953.). 

Deuterium Exchange Reaction of A a Pentenoic Acid. J. chem. Soc. [London] 1940, 1362. 

Utiyama, M. Hattori, H. Tanabe, K. Exchange reaction of methane with deuterium over solid base catalysts. J. Catal. 1978, 53, 237-242. 

Since the associative and dissociative tt complex substitution mechanisms are not mutually exclusive, both may participate simultaneously in exchange reactions where deuterium oxide is the second reagent. It is therefore of interest to distinguish between the relative importance of these two mechanisms. 

Once the dissociative mechanism is established, it is possible to apply Gutmann s theoretical treatment (40) to the elucidation of the rate-determining step of the exchange reaction. For deuterium-tritium double labeling procedures, i.e., D O 100%, TgO 1%, it may be shown that the following normalized equations apply under initial exchange conditions ... 

The comparison of the catalytic performances of metals and their alloys is sometimes hampered by the different degree of deactivation by carbonaceous residues (107, 67). Therefore, it seems appropriate to start with a discussion of the exchange reactions of the hydrogen isotopes protium and deuterium on platinum and Pt-Au films (31). A comparison of this reaction on platinum and its alloy shows that of the two reaction paths possible on platinum in the temperature region studied, one remains unchanged on the alloy but the other, which prevails on platinum except at very low temperatures, seems... 

The exchange reaction of methane with deuterium has been found to show a decrease in specific activity upon alloying of palladium with gold (82), reflecting the decrease in number of reactive surface metal atoms upon alloying. 

The exchange reactions of methane with deuterium over several metals (21, 39,146,147,195, 215, 216, 229) exhibited compensation behavior (Table III, G), as has been pointed out previously (3). No such relationship was found in the data available for exchange reactions of C2-C6 hydrocarbons. This is consistent with discussion given above (see Section III, B, 4) in which it was concluded that the differences in the kinetic behavior of the exchange reactions between methane and the other hydrocarbons varied with the individual metals concerned. 

Table III. The Influences of Certain Coals and Pure Macerals on the Deuterium-Hydrogen Exchange Reaction of Tetralin-d 2 an( Diphenylmethane at 400°C.a...

Table IV. The Influence of Macerals from PSOC-828 and PSOC-1103 on the Deuterium-Hydrogen Exchange Reaction of Tetra-lin-dj and Diphenylmethane at 400°C.a k...

Aromatic positions, deuterium-hydrogen exchange reaction of tetralin-di2 and diphenylmethane, I62t,l63t Aromatic stretching, FTIR of vitrinite, 103-12 Aromatic-to-aliphatic ratios, carbon-13 NMR, 80-95 Aromaticity, 73... 

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