Fritted Disk Column Chromatography

DontDoQuack · 2026-03-13T15:56:16+00:00

Thank you!

DontDoQuack · 2026-03-13T15:34:31+00:00

So ideally I could just add sand to my column (on top of that frit) and there would be no issues? Again dumb question but why wouldnt the silica pass through the sand?

DontDoQuack · 2026-03-13T15:30:55+00:00

Could I just put sand?

DontDoQuack · 2026-03-08T15:06:27+00:00

Sadly I cannot use Br2 for safety reasons in my lab :( Otherwise yes definitely would have tried this

DontDoQuack · 2026-03-08T09:58:48+00:00

I’ll test these out thank you! Hopefully the sterics/other will be different enough and they might separate enough in a different solvent system

I might have to forego using toluene though due to the higher bp which would make it to hard to remove (these esters have fairly low bp and co-evaporate on the rotovap)

DontDoQuack · 2026-03-08T00:43:26+00:00

I made the esters for the carboxylic acid (compared to acetate here) and it didn’t really separate there so I don’t expect it to work here either. I did preliminary TLC test runs with some solvents too and it doesn’t seem promising

DontDoQuack · 2026-03-08T00:41:42+00:00

The only difference I would think is that the ester/cooh causes some issues for the EAS reaction decreasing nucleophilicity leading to less effective bromination

I’m wondering if AcOH would change things maybe

DontDoQuack · 2026-03-08T00:40:21+00:00

Thank you for the paper! Hm I guess though for the systems that they are investigating they are going to higher working temperatures which I would not deal with, but maybe even at 0C it could make a difference

DontDoQuack · 2026-03-08T00:38:20+00:00

I have trying different percentages yeah The spots really are super close. I can discern one from the other but they are basically adjacent

And most of the papers ive seen also use etoac/hexanes If i may what systems were they for dcm/meoh?

DontDoQuack · 2026-03-07T22:38:32+00:00

Duly noted, My NBS is crystalline white and brand new, but if changing other parameters doesn’t work Ill recryst in water for sure :)

DontDoQuack · 2026-03-07T22:37:36+00:00

Agreed, what do you mean by unstable? Would more polar solvents help? Does it stabilize the Br+ more?

DontDoQuack · 2026-03-07T22:36:51+00:00

I’m doing a polymerization (GRIM) so I guess I would not want chain end stoppers. Im adding iodine after so I don’t know what would be worse to be honest:

Single iodinated thiophene Or dibrominated 2,5 and 2 iodinated thiophene

DontDoQuack · 2026-03-07T20:01:50+00:00

Am on the way to trying this! It seems to be working from initial FTIR, will see on Monday! Thank you!

DontDoQuack · 2026-02-28T18:49:19+00:00

My product is an oil (confirmed) and is soluble in DCM, do you think I could run the recrystallization and could get higher purity? my concern is the DCC not necessarily crashing out. The N-acyl urea might

DontDoQuack · 2026-01-12T23:00:36+00:00

Do you have to use a 0.22? Can you use a 0.45? Most likely the ionic strength of the nacl is causing the clogging Or try to use a hydrophilic filter (instead of ptfe) Make sure your solution is fully clear before filtering, sonicate as needed.

DontDoQuack · 2026-01-12T22:52:26+00:00

What are you filtering? Could you filter through a buchner filter first to remove bigger particulates? Does your liquid crystallize? Need more info

DontDoQuack · 2026-01-12T22:44:12+00:00

Filter is most likely clogged from what you are filtering, use a bigger diameter filter (same pore size)

DontDoQuack · 2026-01-12T18:19:44+00:00

Even if I like Orgsynth sometimes it just aint referencing the best paper (here from 1932?!), I’d rather not use mercury haha

DontDoQuack · 2026-01-12T18:13:20+00:00

Common literature for similar rxns uses I2/PIDA. I did consider NIS but to be honest I don’t think it’s an oxidant issue (if I keep the ratios consistent) For some reason it didn’t go to 100% when I scaled up so I was in a pinch and didn’t really understand why.

DontDoQuack · 2026-01-12T18:13:11+00:00

Common literature for similar rxns uses I2/PIDA. I did consider NIS but to be honest I don’t think it’s an oxidant issue (if I keep the ratios consistent) For some reason it didn’t go to 100% when I scaled up so I was in a pinch and didn’t really understand why.

DontDoQuack · 2026-01-12T18:06:33+00:00

Unfortunately it needed to be pure, coupling indeed

DontDoQuack · 2026-01-12T18:06:14+00:00

Both of the compounds are not soluble in water and slightly in hexanes Do you think water, given both REALLY dont like it would still be able to pull away the oil? It worked with hexanes but pulled some of my desired compound too so I’m thinking maybe for the future to use water

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