......a bit about what you wrote. About you Zn can hydrogenate ephedrine. Do you know how I check the amount of Zn in an iron wire? I put a little piece of the wire in a special buret closed on top, then i fill it with HCl, and the H2 developed pushes the liquid down, so I read the number. Development of H2 is nearly istantaneous, giving a lot of effervescence. If you use a thin sheet of Zn the formation of a big quantity of hydrogen is even faster. Now you mean that you can hydrogenate ephedrine so, like Ni, Pd or Pt hydrogenation of a double bond? This means that Zn metallic cristals have the same bravesian lattice of Ni. That's very interesting. Definitely deserves a detailed investigation. But a doubt now: HCl protonizes the alcoholic function, this becomes a good leaving group as H2O, thus forming a carbocation that loses a H+ generating an enamine which (I quote from Rhodium's "P2P from ephedrine derivatives")spontaneously rearranges to the isomeric imine - Schiff base -. It is a reversible equilibrium. Practically the pi orbital shifts at both sides of the N-group bearing carbon, tha same carbon that loses a H atom as H+, thus liberating a sigma doublet that turns to a pi double bond doublet. So we should obtain more than a product. Then if Zn has a catalysing surface, the pi orbital interacts with it, making possible a radicalic hydrogenation. But after a very short time the metallic surface will desappear leaving only Zn++. I don't know, but something doesn't convince me....