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The mechanism for the hydrogenation of alkenes or alkynes using Pd/C is fairly well explained to involve the absorption of hydrogen onto a metal's surface followed by the addition of that hydrogen into the π* orbitals; however, I am having a hard time understanding or finding any literature on the mechanism for the simple hydrogenolysis of benzyl ethers.

I would not expect this to involve the same surface chemistry as the hydrogenation of alkenes/alkynes due to the geometry of the C–N and C–O σ* orbitals; however, the catalyst used, Pd/C, is heterogeneous, so I don't know what other mechanisms could be possible. I found a paper1 that reported the mechanism for hydrogenolysis involving a homogenous catalyst was an oxidative addition followed by reductive elimination; however, I am not sure if this is the same mechanism that applies to benzyl ether cleavage with Pd/C.

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  1. Martínez, A. G., Alvarez, R. M., Aguirre, J. A., & Subramanian, L. R. (1986). Mechanism of hydrogenolysis. Part 1. Catalytic hydrogenation of vinyl and aryltrifluoromethanesulphonates. J. Chem. Soc., Perkin Trans. 1, (0), 1595–1598. doi:10.1039/p19860001595
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    $\begingroup$ While the mechanism you show seems like obvious thing, it's very sketchy and perhaps even incorrect. Heterogeneous mechanisms are problematic... $\endgroup$ – Mithoron Nov 2 '20 at 1:07

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