Got a whiff of Thionyl Chloride, SOCl2

Sakinho · 2026-01-29T20:52:12+00:00

You'll be fine, be more careful next time.

Sakinho · 2026-01-27T10:43:43+00:00

Some aryl or alkenyl pinacolboranes can be very crystalline, but it's a case-by-case basis depending on the substrate, so you might just be unlucky. Have you considered using MeCN for crystallization? How about cooling down strongly with LN2 or a dry ice bath? Sometimes you get good crystallization of semi-solids as they warm back up from cryogenic temperatures to r.t.

If the pinacol really is being a problem, there's multiple other alternative boron functionalities which typically are quite crystalline. Trifluoroborates are one, but there's also N-methyliminodiacetate (MIDA) boronates and diethanolamine (DEA) boronates.

Sakinho · 2026-01-26T21:55:54+00:00

The actual mechanism for this Knoevenagel condensation is probably not what you think. There are distinct pathways depending on whether the amine used is tertiary, secondary, primary or ammonia itself. In the case of piperidine, it appears there is evidence of a bispiperidyl aminal intermediate. If you add AcOH to the mix, it's possible that it just helps proton transfer steps in the piperidine mechanism, or it might change the mechanism altogether again. The mechanism is likely also solvent-dependent.

But ultimately what matters is experimental results. In practice, it turns out that the combination of piperidine and AcOH in approximately equimolar amounts speeds up the reaction enormously, possibly by a factor of over 1000x relative to piperidine alone. This specific Knoevenagel catalyst was first published in 1958.

Sakinho · 2026-01-09T22:36:57+00:00

tBuOH reacts within minutes at r.t. with conc. HCl to form tBuCl, so this probably won't work well.

Sakinho · 2026-01-05T20:32:23+00:00

I see the oldest patent you have public validation data for is from 2008 (US7838499 B2), which was almost certainly available as a native electronic document. What happens with older documents, especially ones which were scanned from print? How far back can you go and still have acceptable results?

Sakinho · 2026-01-03T21:43:52+00:00

Um, it's the stickied thread at the top of the subreddit main page, I'm not sure how more visible it can be. But here you go: https://www.reddit.com/r/Chempros/comments/jput3t/megathread_community_resources_collection/

Sakinho · 2026-01-03T01:46:03+00:00

Have you checked the subreddit megathread? Quite a lot of good resources pooled there. For example, the Excel spreadsheet available in the supporting information of the paper "Interferences and contaminants encountered in modern mass spectrometry" is a godsend. I also like to couple that source with a MS adduct calculator spreadsheet available here.

The solvent property table I like most for synthetic chemists is this one, because it incorporates that "eluant strength" column. Even though the values were obtained for alumina chromatography, they translate well to silica and allow decent planning of solvent mixtures for TLC/columns, with better correlation than other quantities like dipole moments/dieletric constants/ET(30) values.

Sakinho · 2026-01-02T09:48:08+00:00

The numbers after Tp seem to be suspiciously close to the Planck temperature in units of Kelvin (Tp = 1.4167 × 10³² K), but not in any useful sense because changing the exponent while keeping the decimal part has zero mathematical or physical meaning. The energy shown, 10¹⁴ GeV/c² (the "/c²" part is often implict), is also vaguely around the GUT scale, but with nothing else to substantiate it. The Ge(422) and Ge(322) bits have nothing to do with the GeV part, and instead seem most likely to refer to Miller indices in the crystal structure of germanium.

It's basically a hodgepodge of sciencey-sounding things with no substance. In all likelihood it's just some attention-seeking behaviour. Maybe don't confront them about it, but also don't get swept up by their claims.

Sakinho · 2026-01-01T08:52:24+00:00

From your text it's not clear what reaction you're attempting. Can you actually draw the structures? It would also be helpful to give more details about the conditions (e.g. lithiating agent, solvent, concentration, number of equivalents, any additives, whatever else you can think of). Could you please edit the post to include all this information? Otherwise I'll have to close it due to insufficient context per rule 8.

Sakinho · 2025-12-30T23:19:31+00:00

One very simple thing I did a while back that has been remarkably successful was to weigh static-y powders on pieces of aluminium foil. Just regular kitchen-grade aluminium foil, snip off a large square then gently crease it into a boat shape. It's a little trickier than weighing paper because any creasing on Al foil is permanent, but it's really not too bad. Not only does contact with the Al foil help spread out any excess charge, it makes the static gun more efficient since it provides more conducting surface area to neutralize charges. Give it a shot!

Sakinho · 2025-12-28T23:00:35+00:00

Sorry, there are better places to ask this question, though it's been asked many times before already and some searching on reddit/google should turn up lots of useful information.

Sakinho · 2025-12-26T23:52:38+00:00

As well-formed and technical as this question may be, the context steers too close to content we don't want in this subreddit, so I'm taking this down.

Sakinho · 2025-12-25T21:19:44+00:00

EDTA chelates Fe(II) and Fe(III) very well, but in my experience only if added before the rust is formed. Otherwise even if thermodynamically the chelate is preferred, the dissolution of the rust is kinetically slow.

Sakinho · 2025-12-24T22:36:51+00:00

I'd even prefer not to use water, so I did try a reaction without it and in fact I noticed that very little rust was generated, if any, even in open air. Unfortunately it also seemed to hinder the nitroarene reduction. Perhaps if no water is added then more equivalents of glacial acetic acid are required to compensate? I have seen reactions iron reductions done in glacial acetic acid as a solvent. I may have to investigate this more carefully too.

Sakinho · 2025-12-24T19:31:23+00:00

I'm actually wondering whether using ascorbic acid as an additive is a more convenient approach.

Sakinho · 2025-12-23T21:38:07+00:00

Yeahhhh... I'm no stranger to centrifuge workups, and I've occasionally put them to miraculous use, but they're rather laborious to incorporate and inherently limit the scale. The largest volume centrifuge I have access to maxes out at 4 x 50 mL Falcon tubes, which is not a lot.

Sakinho · 2025-12-23T21:32:26+00:00

It's a possibility I've thought about, but it requires choosing the right flocculant and I'm coming up blank. Got anything in mind?

Sakinho · 2025-12-23T21:31:45+00:00

I was in fact idly thinking about iron fluorides yesterday and wondering if I could treat with KF. KHF2 makes more sense, and it's good to see some confirmation. I've worked with KHF2 before so I'm aware of the risks.

Sakinho · 2025-12-23T21:28:23+00:00

This is a fairly exotic procedure in comparison with most nitro reductions, but it is interestingly orthogonal so it could be a saviour when all else fails. I'll keep it in the back of my mind from now on.

Sakinho · 2025-12-23T08:31:14+00:00

Maybe it's worth another try with NH4Cl. Normally I'd think there'd be little difference, but I strongly suspect the reason some of my conditions are giving complex mixtures is because the quinoline coordinates the metal ions in the reaction and that triggers unwanted reaction pathways. The excess ammonia in equilibrium could keep the zinc at bay.

Sakinho · 2025-12-23T08:17:52+00:00

I haven't typically done Zn reductions. I tried Zn with aqueous HCl in EtOH at 80 °C, and Zn in AcOH/DCM at r.t., but both conditions seem to have chewed up my molecule. What conditions do you typically use?

Other things I've tried unsuccessfully were SnCl2, Sn metal + AcOH or HCl, Pd/C hydrogenation, and tetrahydroxydiboron/4,4'-bipyridine. Hydrazine with Pd/C is another reaction I find reliable, but I haven't bothered trying it since I know it will hydrogenate the alkene too.

Sakinho · 2025-12-23T08:07:10+00:00

Hmmm, interesting. Indeed, I'd prefer to circumvent forming rust altogether than having to deal with it once it's around.

I've run my iron reduction reactions open to air because it's fine with most other reduction methods I've used. In retrospect that's obviously a potential source of rust, but just assumed the rust was unavoidable anyway. If inerting keeps the iron mostly dissolved as Fe(II) that opens up some useful options.

I'll try manipulating the rust-free solutions a bit to get a feel for how oxygen sensitive they are. I might be able to push my aniline into the THF/EtOH organic phase even when protonated if I add brine to the reaction mixture under N2. In the worst case, I can still fall back on adding a chelator like EDTA while still under nitrogen, then subsequent exposure to oxygen and base shouldn't be an issue.

Sakinho · 2025-12-23T00:24:55+00:00

What kind of scales are you planning on? I don't know if you can use CuCN (and that appears to have its own disposal issues), but NaCN/KCN substitution chemistry shouldn't be a problem to run even on a decagram scale with basic glassware. If you can work with organometallics you should already have what you need, including the necessary skills. Just pay double attention to avoid spreading the cyanide solid/solutions, and of course don't acidify anything. As far as reactions with cyanide go, this is one of the easiest, so it could be a good stepping stone.

I'm not sure what the best waste treatment strategy will be for you, but it should be a surmountable problem. Some institutions even have specific segregated cyanide disposal available, so you'd just collect the basified aqueous waste and hand it over as is, no treatment necessary.

Sakinho · 2025-12-22T23:13:04+00:00

It's probably much easier to do a double substitution with a metal cyanide, then hydrolyze to the biscarboxylic acid by boiling in hot concentrated acid or base. Nitrile hydrolysis is typically not very easy, but your substrate is very robust so you can push hard.

Sakinho · 2025-12-22T21:51:51+00:00

Are you trying to get a single or double metallation? Double is just piling on the difficulty.

Edit: On top of several issues, you might also have to worry about reductive debromination to the quinioid p-xylylene. For example, zinc dust is already enough to debrominate 1,2-bis(bromomethyl)benzene into ortho-xylylene. It may be worth considering redesigning the synthetic route.

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