As shown in Figure 14.24, the first step in the heterogeneous hydrogenation of ethylene is adsorption of the ethylene molecule on a metal surface. One proposed explanation for the “sticking” of ethylene to a metal surface is the interaction of the electrons in the C—C p bond with vacant orbitals on the metal surface.

(a) If this notion is correct, would ethane be expected to adsorb to a metal surface, and, if so, how strongly would ethane bind compared to ethylene?

(b) Based on its Lewis structure, would you expect ammonia to adsorb to a metal surface using a similar explanation as for ethylene?

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Hydrogen Carbon gH, and GH, ad sorbed on metal surface 2 After HH bond breaks, H atoms migrate along metal surface One free H has attached to GH, to form CHs (ethyl group) intermediate 4 Second free H about to attach to GHs intermediate to form CH, Ethane, CH, desorbs from metal surface