Pd/C

pekebaz3 · Sat Jun 11, 2005 9:50 am

What exactly is the Pd/C in this reaction? Is it a typo? Is it PdCl? Help!

Catalytic Transfer Hydrogenation of Crude 2,5-dimethoxynitroethane

The crude product of the previous step was dissolved in 400mL MeOH and placed in a 1L RBF equipped with a stir bar. In a separate beaker away from all combustible materials, 1g of 10% Pd/C was carefully wetted down with MeOH and the resulting slurry transferred to the rxn flask. To the rxn flask was added 62g ammonium formate. The flask was equipped with a reflux condensor, a piece of tubing was attached to the top of the condensor, and the end of the tubing was submenged in a container of water (this works to exclude O2 from the rxn while allowing the evolving CO2 to escape). The rxn was gently refluxed for 24 h (CO2 evolution), cooled, filtered through celite to remove the Pd/C, and the solvent evaporated. The residue was taken up in 150 mL of Et2O (or toluene) and 300 mL of H2O and the pH adjusted to >12 with 20% NaOH. The mixture was transfered to a sep funnel, shaken, and separated. The aqueous layer was extracted with 2x100 mL portions of Et2O (or toluene). The combined organics were dried over MgSO4, filtered, and gassed with HCl (2C-H*HCl is partially soluble in DCM, so don't gas in that solvent). The resulting white crystalline solids were filtered, washed with Et2O, and allowed to air dry to give 2C-H Hydrochloride.

sony · Sat Jun 11, 2005 1:34 pm

No this is is palladium on carbon (10% Pd by weight)

anime · Sat Jun 18, 2005 1:02 pm

more commonly referred to as Palladium on Charcoal Smile

the alchemist · Mon Jun 27, 2005 3:41 am

Be careful with this stuff especially when you don't even know what Pd/C is. I have witnessed a very loud explosion at 8:00 in the morning when someone was exposing this stuff to a Parr flask saturated with MeOH vapor. The catalyst fluttered to the floor, smoking and sparkling and even set some notebook paper on fire. That was with >100 mg. The guy was in momentary shock and then began checking himself to see if he still had limbs. This stuff laso sputters some sparks when sitting out in the air.

It would be wise to blow the flask out with nitrogen before adding the catalyst + MeOH to remove any O2.

respect...

icecool · Insistent Chemist

How the fuck could that happen...
Pd/C isn't a dangerous material like LAH right?
And Pd can't be oxidized so I don't see the problem here...
Is it because of the ammonium formiate?
Since if one could get Pd this would be a nice alternative for the Hg reductions and LiAlH4.
It can be re-used every time (if I get it correctly).

primathon · modified

It's a nice alternative to LiAlH4, but it's freakishly expensive, somewhere in the vicinity of >$700/oz if I remember correctly.

Also, I'm pretty sure it's very difficult to recover any Pd/C used in the reaction.

the alchemist · Fri Jul 01, 2005 7:44 am

It is most definitely difficult to recover active catalyst after the reaction. Pd/C produces sparks sometimes when exposed to air. I guess that the carbon is so activated by the Pd that it burns on contact with air. This does not happen all the time but can... especially if you are weighing out large amounts. Raney Ni is the same way... At best, have some nitrogen on hand to flush your flask and you should be ok. Minimally, just make sure you add the solvent TO the Pd/C in the flask and not the other way around. You very well could possibly witness the above mentioned situation.

2spun · The Resistor

ware yer gloves and eye protection,
it does and can get mean on ya.
swiy likes to learn the hard ways.

lab saftie

stratosphere · Fri Jul 01, 2005 9:12 am

joe_aldehyde · huxleys associate

when using Pd/C in reductions, especially CTH conditions, does it absolutely have to be prereduced under light H2 pressure? i have a bottle of H2 but no reducing valve and nor am i comfortable pressurizing my glassware.

anime · Tue Jul 05, 2005 10:58 pm

anime · Thu Aug 04, 2005 2:21 am

Pd/C is easy to recycle, and recover from the reaction. Post reaction material is filtered through celite. Rinsed once or twice with methanol, then washed with distilled water.

You can put the catalyst in a KOH solution to reactivate it, the catalyst unless poisoned can be used several more times, Smile

Raney Nickel should also work in this reaction. I'm sure urushibara would work too, but I haven't tried it.