Catalytic Hydrogenation

[umdnjmed]

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Does catalytic hydrogenation of an alkene form enantiomers? in other words, does syn addition occur on both faces of the molecule?

Also, what difference would an E vs a Z reactant make during catalytic halogenation?

Thanks!

 

[jdlykins91]

Catalytic hydrogenation of an alkene forms an alkane. Concievably the metal (platinum, etc.) could catalyze the addition to either face, so long as it is a syn-addition. But it does not form enantiomers because there is no difference between the alkanes. As far as I know, there is no difference in the product depending on the geometric arrangement of the reactant (either E or Z). Does that all make sense?

 

[CodeRedDew]

Does catalytic hydrogenation of an alkene form enantiomers? in other words, does syn addition occur on both faces of the molecule?

Also, what difference would an E vs a Z reactant make during catalytic halogenation?

Thanks!

Catalytic hydrogenation DOES cause enatiomers to form. You have to think of this way: If H2 can attack from both faces of the alkene then the groups that are already attached to the alkene can be pushed two different ways (opposite of where ever the H2 attacks). See the attached photo for an example of how enantiomers are formed during hydrogenation.

As far as your second question goes, different starting stereochemistry will produce different stereochemical products during hydrogenation. See the other attached photo below for an example (ignore the "+" symbol, I didn't know how to get rid of that in the chemaxon program)

 

[jdlykins91]

I would defer to him. I made a mistake.