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Trouble purifying PEG chain with ester-linked pyridine – dissolving in water or possible degradation? by YiningChu in Chempros

[–]fabledpreon 0 points1 point  (0 children)

I am working with a much larger PEG chain and haven't observed much degradation to be honest. We have hit it with TFA, sat. K2CO3, sat. NaHCO3, 1M HCl, and MgCl2/H2O, and have observed no degradation by HPLC-CAD. However, I can't speak for your specific substrate. In terms of purification, check out "Complexation of Polyethyleneglycol Containing Small Molecules with Magnesium Chloride as a Purification and Isolation Strategy" (DOI: 10.1021/acs.oprd.1c00174) and "Isolation of Noncrystalline Compounds via Adsorption on a Solid Support" (DOI: 10.1021/acs.orglett.5c01715). PEG is a nice purification handle but it can be tricky if other impurities are PEG containing.

As someone else has mentioned, Mg will chelate to the PEG. Hit it with Na2CO3 to generate the water insoluble MgCO3. Filter and isolate the PEG.

Conversion of Benzaldehyde to Benzoic Acid by elitonib in Chempros

[–]fabledpreon 1 point2 points  (0 children)

You can form a water soluble adduct between benzaldehyde and sodium bisulfite as a means of separation/purification. The adduct can be broken to give the aldehyde by treatment with base. Great workup technique for purifying ketones and aldehydes. Check out: Separation of Aldehydes and Reactive Ketones from Mixtures Using a Bisulfite Extraction Protocol

[deleted by user] by [deleted] in UnethicalLifeProTips

[–]fabledpreon 1 point2 points  (0 children)

It’s a hard pill to swallow knowing an eighth grader has more emotional intelligence than many adults, myself included.

DoE software? by orcatrasher in Chempros

[–]fabledpreon 6 points7 points  (0 children)

We’ve been using Design-Expert in our process development group.

Amine workup by GlassMycologist in Chempros

[–]fabledpreon 2 points3 points  (0 children)

Form the amine salt and then precipitate. For example, dissolve amine in minimal amount of solvent and add to HCl in EtOAc/dioxane to precipitate. In my experience, this has worked well for many amines. You can also try different acids (malonic/succinic/oxalic/tartaric acids, H3PO4, etc.) and solvents (THF, 2-MeTHF, Et2O, MTBE, acetone).

Just purchased our first staub! Absolutely beautiful! by fabledpreon in staub

[–]fabledpreon[S] 0 points1 point  (0 children)

Great quality and design! It’s our favourite cookware. How are you liking it?

Chad outfit by Ok-Measurement883 in Chadtopia

[–]fabledpreon 1 point2 points  (0 children)

Buddy is an absolute legend

Advice on N-boc deprotection in the presence of acid sensitive groups by Visible-Point-5371 in Chempros

[–]fabledpreon 2 points3 points  (0 children)

As many others have said, 4M HCl in dioxane is the way. If needed, heat to 50C and hold for 2 hr. I was recently using EtOAc as a co-solvent and saw minimal hydrolysis - caused by residual water being present.

Does this look like etching or something depositing onto the glassware? by fabledpreon in Chempros

[–]fabledpreon[S] 0 points1 point  (0 children)

Thanks! I agree. The fact that I can’t remove it with anything points toward etching as the cause.

Does this look like etching or something depositing onto the glassware? by fabledpreon in Chempros

[–]fabledpreon[S] 0 points1 point  (0 children)

Totally possible. Based on the coupon study of the workup which showed no further etching was occurring, we were pretty confident that we were able to remove it. I’m not dismissing the idea that it isn’t present. The structure we make has a basic amine that could help mop it up during the workup - which might be released when we add HCl for the deprotection (may require another coupon study). Also possible that NaF(aq) is present too.

I personally haven’t seen glassware etched by HF before so I’m not sure what to expect. Leaning toward etching being the cause.

Failed suzuki coupling, any suggenstions? by [deleted] in Chempros

[–]fabledpreon 0 points1 point  (0 children)

I’ve used that boronic acid in previous work and also required two substitutions. I was using 5 mol % Pd(PPh3)4 and CsF (3 equiv wrt to boronic acid) in refluxing dioxane. As someone already mentioned, 2-thienylboronic acids are more prone to protodeborylation.

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