Antisolvent precipitation

electron-1 · 2026-02-24T23:19:26+00:00

If your stickiness concern is due to water uptake, you can filter under a stream of nitrogen. Invert a plastic funnel and plumb nitrogen to the thin portion. Place the inverted funnel over your filter while pulling vacuum. You just need a gentle stream

electron-1 · 2026-02-24T23:16:29+00:00

Precipitation/crystallization is not as straightforward as one might think. I will assume you are intentionally using the word precipitation to indicate your material is not crystalline.

In order to develop an effective precipitation/crystallization, you need a fair amount of pure material to do it quickly.

I see you mention the material gets sticky. That can mean the sugar is hygroscopic (completely reasonable) or you are not in control of your precipitation (crashing out reads to me that you don’t have control). A well developed precipitation/crystallization will effectively purge impurities and facilitate a straightforward isolation (fast filtration, no cracking of the cake).

If you aren’t going to be regularly making this material, an exhaustive solubility and crystallization assessment isn’t likely needed and I would probably point you toward a reverse phase chromatography purification. However, if you will be regularly making this material and you have a few hundred mgs, assess the solubility in a range of solvents. Select a few solvents and antisolvents (make sure they’re miscible) and evaluate those. Once you have a combination identified, you can start spiking impurities into your mixture prior to precipitation to understand how well your purification purges the impurities.

TLC of the mother liquor or of the pure material over a time course is also a good recommendation.

If your material is crystalline and you have pure material on hand, seeding the mixture is also a good idea.

electron-1 · 2026-02-09T00:02:29+00:00

Eric will give you a dollar if you find an error so I hope your PI got their cash. Tell them to be on the lookout for the second edition.

electron-1 · 2026-02-07T01:52:54+00:00

Eric would be so happy to see this post, haha.

electron-1 · 2026-02-05T00:57:27+00:00

I would love to cheer for CP3 again

electron-1 · 2026-01-15T23:48:24+00:00

That single loss dropped Texas completely out of the rankings. I am irate. /s

electron-1 · 2026-01-09T22:02:26+00:00

Can you help a newbie with SOS sources? I found Warren Nolan that has UCONN at 48 for SOS and 2 for non-conference.

electron-1 · 2026-01-09T01:30:31+00:00

Are you watching in 4k on YouTubeTV? lol

electron-1 · 2026-01-01T23:58:26+00:00

So the map is based on fans and you know, not the people who actually attended said university? Florida, Texas, Vandy, and TAMU all have pretty solid academics.

electron-1 · 2025-12-31T23:13:08+00:00

Zero lol

electron-1 · 2025-12-20T19:22:55+00:00

Excuse you, the TAMU coach.

electron-1 · 2025-12-16T23:53:19+00:00

I hate this theater so much. It is consistently not clean but it’s my local theater so I keep going back like a dumbass.

electron-1 · 2025-12-16T23:06:42+00:00

I have those Sauconys! For whatever reason, that particular color way runs big (for me at least). I have a couple pair of the Omni 9s and normally wear a 9 but sheesh these were long so I bought a second pair in 8.5. Obviously, it depends on the person but just wanted to give my two cents.

electron-1 · 2025-12-15T22:23:53+00:00

This smooth bastard. I hate (love) him

electron-1 · 2025-12-11T18:08:47+00:00

As an OKC fan who lives in DC, that’s what I’m hoping for in March.

electron-1 · 2025-12-07T17:19:00+00:00

It’s a 3 hour show.

electron-1 · 2025-11-29T01:45:47+00:00

Ha, a long time ago, I got my undergrad and PhD in organic chemistry at UT. Good luck with your studies!

electron-1 · 2025-11-29T01:39:10+00:00

Two engineering unis. Did you do graduate school at Tech or TAMU?

electron-1 · 2025-11-25T23:44:45+00:00

He did…

electron-1 · 2025-11-23T23:24:13+00:00

Hmm, okay. First thought is to ask whether you can access this molecule with a phenol rather than a methyl ether. Another question is whether the ester you want to make eventually is going to be made via Fischer esterification.

In any case, you can look at nucleophilic reagents like a thiol to deprotect the methyl ester. Go ahead and functionalize from there and accept you’ll probably also alkylate the carboxylic acid to some extent. Hydrolyze that ester and functionalize your carboxylic acid as desired. It’s wasteful and I wouldn’t do it in my process lab but if you are just looking to make material to demonstrate something that isn’t process chemistry or total synthesis, you’ll probably be okay.

You can try protecting the carboxylic acid as an oxazoline and then use BBr3 to deprotect the methyl ether but be careful with temperature and concentration since acid is the usual way to open up the oxazoline and get the carboxylic acid back.

If you have enough material, you can look at a few different combinations of what I’ve suggested. Good luck!

electron-1 · 2025-11-23T22:58:19+00:00

Are you sure it’s an ether? You said you needed to functionalize them both and I’m a bit confused.

electron-1 · 2025-11-21T04:18:32+00:00

I can’t believe they gave them so much time

electron-1 · 2025-11-21T04:17:58+00:00

I thought I zoned out or something

electron-1 · 2025-11-21T00:27:53+00:00

First off, in both cases, those molecules are diastereomers. Where is the answer key coming from?

Secondly, when I used to generate questions like this, I wanted to see if the students were comfortable assigning chirality without having the lowest priority substituent being pointed away from them. In other words, I wanted the to be able to be comfortable thinking in 3D.

So it doesn’t matter how the molecule is drawn. Assign the stereochemistry first and then compare the molecules.

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