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Chemistry Forums for Students => Organic Chemistry Forum => Organic Chemistry Forum for Graduate Students and Professionals => Topic started by: SateliteX on February 15, 2022, 02:24:31 PM

Title: Pd Eluting Down Silica Column
Post by: SateliteX on February 15, 2022, 02:24:31 PM

I did a Suzuki coupling using Pd(PPh3)4 with a solvent system of 10:1 THF & water. After l-l extraction with ethyl acetate and water, the organic fraction was dried over MgSO4, reduced and fused to silica. The crude was loaded onto a silica column and purified with 7:3 EtOAc:Hex, which was alright except for some brown stuff coeluting with my product - which was probably some of the dead Pd catalyst?

I tried to redissolve my Pd-contaminated product with toluene and filter through celite, didn't work out. Also tried to remove Pd with charcoal, also didn't work out. I am one step away from ordering Pd scavenger. Could someone offer any advice on how to get rid of the brown contaminant?

Thanks in advance.

Title: Re: Pd Eluting Down Silica Column
Post by: Guitarmaniac86 on February 15, 2022, 02:35:21 PM

Are you certain it is palladium? What were the starting materials and what is the expected product? Anything with nitrogens or nitro groups in them? These can give brown colours.

I would be very surprised to see palladium come through at 30% EtOAc. Have you TLC'd it to see if there is more than one product in there? Have you tried to run a slow gradient starting from 0% EtOAc and moving up to 30% EtOAc to see if you can remove the potential impurity that way?

Title: Re: Pd Eluting Down Silica Column
Post by: SateliteX on February 15, 2022, 05:29:07 PM

Hi, the fractions are pure by TLC, and the EtOAc are 70% so I'm not sure if that's the reason

Title: Re: Pd Eluting Down Silica Column
Post by: wildfyr on February 19, 2022, 02:22:42 PM

Stir with activated carbon?

Title: Re: Pd Eluting Down Silica Column
Post by: rolnor on February 20, 2022, 01:04:20 AM

Does it matter? Is the product OK on NMR?

Title: Re: Pd Eluting Down Silica Column
Post by: phth on February 20, 2022, 03:07:56 AM

Be careful; palladium nanoparticles pass through nitrile gloves and typical filtrations easily.

Title: Re: Pd Eluting Down Silica Column
Post by: rolnor on February 20, 2022, 05:07:56 AM

Its not Palladium, its something else I think.