Argon (Stranger)
03-28-03 19:06
No 422038
      Rh/C hydrogenation  Bookmark   

In his TMA-2 post Barium said in one of the notes that he could have hydrogenated the corresponding oxime with Pd/C, instead of Raney Ni, but he would have to use 3x molar equivalent of GAA to push the equilibrium of the reaction to the right.

What would that molar ratio be (product/GAA) if using Rh/C?

Rhodium, I am guessing you would know that.
(Hive Addict)
03-30-03 12:25
No 422468
      Rh/C  Bookmark   

This is what I said in the note:

Note 2.
Nickel is chosen over Pd here because if Pd is used, about three moles acid/mol oxime has to be used to minimize side reactions like imine and/or hydroxylamine formation. This can damage the TMA-2 molecule if a strong acid such as sulphuric acid is chosen. With Raney-nickel the acid is not necessary. Furthermore, Pd can be poisoned by amines whereas Ni canīt.

When reducing oximes secondary and tertiary amines can be formed, especially with Pd as the catalyst. Pd can also be poisoned by the product amine. To avoid all of these things about three moles acid/mole oxime is added. If Rh is the hydrogenation catalyst it is usually enough with just slightly more than the equimolar amount of acid.

03-30-03 21:31
No 422563
      Is this from Friefelder?  Bookmark   

Barium is without question one of the smartest bees on the Hive. Thank you Barium.

P.S. How did you come up with that answer? Is this from Friefelder? I have searched online for days, and could not find anything related to the topic.

Bzzzzz, Bzzzzzzzz, Bzzzzz
03-30-03 21:58
No 422569
      Asymmetric Hydrogenation  Bookmark   

Did anyone identify a chiral ligand for producing levo (R), and dextro (S) Honey? in an asymmetric hydrogenation reaction?
(Chief Bee)
03-30-03 22:35
No 422574
      Chiral honey (not counting D-Fructose/D-Glucose ;)  Bookmark   

Yes, see Post 421261 (Rhodium: "Stereoselective (S)-MDA synth via the Cyanohydrin", Novel Discourse) and also ../rhodium/djvu /imine.hydrogenation.djvu for further reading.