The Reaction of Ethyne with Deuterium

As was the case with ethene and other alkenes, replacing hydrogen by deuterium and analysis of reaction products reveals hitherto hidden aspects of reaction mechanism. Early work with platinum and nickel indicated that neither 

TABLE 9.2. Initial Distributions of Deuteroethenes from the Reaction of Ethyne with 

Inspection of Table 9.3 shows that the values of s, q are all between 60 and 90%, suggesting (as noted above) that variation in the vinyl reversal term p is chiefly responsible for differences in the ethene distributions. This is indeed so its values are high in Groups 8 and 9, accounting for the high deuterium numbers 

TABLE 9 J. Reaction of Ethyne with Deuterium Range of Values of s and ( -p) 

Similar trends in product distributions were found with each metal increasing temperature led to less ethene-r/2 and a broader distribution, and this was also the case when the ratio Pn/Pc was decreased. These two effects are linked, because the parameter p is lowered in each case, this being due to a decrease in the concentration of adsorbed hydrogen atoms and/or vinyl radicals. 

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