March 29, 2024, 05:41:54 AM
Forum Rules: Read This Before Posting


Topic: procedure for reduction  (Read 6118 times)

0 Members and 1 Guest are viewing this topic.

Offline sambasivarao

  • New Member
  • **
  • Posts: 3
  • Mole Snacks: +0/-0
  • Gender: Male
procedure for reduction
« on: March 01, 2007, 07:29:01 AM »
i wnat do reduction with palladium catalyst what is the procedure for that? is it have to do in autoclave?

Offline Dan

  • Retired Staff
  • Sr. Member
  • *
  • Posts: 4716
  • Mole Snacks: +469/-72
  • Gender: Male
  • Organic Chemist
    • My research
Re: procedure for reduction
« Reply #1 on: March 01, 2007, 07:59:19 AM »
Do you mean catalytic hydrogenation with a Pd on charcoal catalyst?

There are tons of papers with preps for this reaction.

I have done this reaction several times to convert R-I --> R-H

I tend to use 10-15% by mass (of substrate) of 10%Pd on C (ie. 1-1.5% Pd by mass).
Degas your solution under Ar.
Stir under hydrogen.
Do not let oxygen (ie. air) into your reaction vessel if hydrogen is present, it's dangerous.
Solvent: Ethanol
My research: Google Scholar and Researchgate

Offline movies

  • Organic Minion
  • Retired Staff
  • Sr. Member
  • *
  • Posts: 1973
  • Mole Snacks: +222/-21
  • Gender: Male
  • Better living through chemistry!
Re: procedure for reduction
« Reply #2 on: March 01, 2007, 01:46:55 PM »
This reaction works in lots of other solvents too, but alcohol solvents are usually the fastest.  I've always thought that EtOAc is a good starting point for solvent.

Be careful when you filter your reaction when it is finished.  Pd/C can sometimes ignite when exposed to oxygen, so try to avoid letting it dry out completely.

Offline Dan

  • Retired Staff
  • Sr. Member
  • *
  • Posts: 4716
  • Mole Snacks: +469/-72
  • Gender: Male
  • Organic Chemist
    • My research
Re: procedure for reduction
« Reply #3 on: March 01, 2007, 02:27:30 PM »
yes, and use a deep celite pad, the Pd/C will go straight through a sinter.
My research: Google Scholar and Researchgate

Offline Custos

  • Full Member
  • ****
  • Posts: 217
  • Mole Snacks: +32/-0
  • Gender: Male
Re: procedure for reduction
« Reply #4 on: March 01, 2007, 06:33:45 PM »
Do you mean catalytic hydrogenation with a Pd on charcoal catalyst?

There are tons of papers with preps for this reaction.

I have done this reaction several times to convert R-I --> R-H

(pedantic alert!) The reaction you describe is strictly a hydrogenolysis, not hydrogenation. Hydrogenation is addition of hydrogen across, for example, a carbon-carbon double bond.

I'll never forget this because a colleague of mine had used "hydrogenation" instead of "hydrogenolysis" throughout a PhD thesis and one of his examiners picked him up on it. This was in the 1970's so pre-wordprocessors, and he had to have the entire thesis retyped correcting the word hundreds of times.

Offline Dan

  • Retired Staff
  • Sr. Member
  • *
  • Posts: 4716
  • Mole Snacks: +469/-72
  • Gender: Male
  • Organic Chemist
    • My research
Re: procedure for reduction
« Reply #5 on: March 01, 2007, 06:46:53 PM »
Ha, thanks for the heads up, I'm going to start writing my masters thesis soon.
Makes sense, since you have hydrogenolysis of Bn groups etc.
My research: Google Scholar and Researchgate

Offline pantone159

  • Mole Herder
  • Chemist
  • Full Member
  • *
  • Posts: 492
  • Mole Snacks: +54/-6
  • Gender: Male
  • A mole of moles doesn't smell so nice...
    • Go Texas Soccer!!
Re: procedure for reduction
« Reply #6 on: March 01, 2007, 07:23:18 PM »
P.S.  What is the proper disposal method for pyrophoric metal catalysts like Pd, Raney Ni, etc.
My books say to always keep them covered in water, but that seems hard to do forever (unless you dump them in the ocean!)

Offline DaveD

  • Regular Member
  • ***
  • Posts: 20
  • Mole Snacks: +3/-0
  • Gender: Male
Re: procedure for reduction
« Reply #7 on: March 01, 2007, 08:45:57 PM »
I would imagine proper disposal of precious metal catalysts would be handled by hazardous waste technicians at your institution.  These catalysts are usually recycled (since they are precious).  And you are correct, they should be stored under water.

One other suggestion - water wet palladium on carbon catalysts are usually much less prone to the ingition risk mentioned by movies.  (I've had a number of small fires on the filter when filtering of dry palladium on carbon catalyst from organic solvent, but not when using water wet palladium on carbon catalyst).

Offline movies

  • Organic Minion
  • Retired Staff
  • Sr. Member
  • *
  • Posts: 1973
  • Mole Snacks: +222/-21
  • Gender: Male
  • Better living through chemistry!
Re: procedure for reduction
« Reply #8 on: March 01, 2007, 09:56:41 PM »
(pedantic alert!) The reaction you describe is strictly a hydrogenolysis, not hydrogenation. Hydrogenation is addition of hydrogen across, for example, a carbon-carbon double bond.


Ohh!  Nice catch!

Sponsored Links