Just having to get rid of it, with my 1 g of product in 10g of crown, would give me a pause. The Ammonia is biodegradable (also known as “fertilizer) and the side product is NaCl, Na2SO4, or NaOAc depending on how you quench it. Yes. Lett. Some aromatic compounds demonstrate quite significant affinity to electron, and can form stable in solution carbanions. Why is a link in an email more dangerous than a link from a web search? Why is Soulknife's second attack not Two-Weapon Fighting? Never done one, but brings back memories of my undergrad. And if you’re doing it on scale as Kowalski did for the Tagamet alcohol, you can distill the ammonia back and forth between two reactors for years. (NH3 is currently shipped in aluminum tanks, not steel tanks?). I like my freedom and this is just a hobby of mine. Lithium amide on the other hand is somewhat more expensive but perhaps more importantly seems to age on standing – no matter how carefully you store it. Melting point of sodium is fairly close to toluene boiling point. Even as recently as 2010, the reaction of pyridines with DCM could get you a paper in J. Org. Using water as a high density storable hydro-lox propellant. Arthur Birch had originally used Sodium (Na), … Synthetically, this reaction seems to behave very similarly to the classic Birch, but with no ammonia and no alkali metals, of course. I guess, that mixture of dry tetramethylethyleneamine and some primary/secondary amine should work. Now this new protocol requires the use of a somewhat expensive 15-crown-5 (the cheapest source I could find is Oakwood for 120USD/100g) that has MW= 220 and has to be used in large excess (6 to 9 equivalents) in the reaction. Ahhh the Birch. It invites curiosity from DEA. I got what I needed before that happened and the reaction worked, but man that was a quick way to waste the rest of the bottle. So if I were to use a cold finger I could condense the gas immediately before the reaction, and that would only take some cheap dry ice? I object to being tarred with ‘misleading lies’. To break compounds’ aromaticity, chemists commonly rely on the 74-year-old Birch reduction, which uses sodium metal and ammonia. Thank you for poking me here. Of course, sodium in an alcohol solvent is yet another old-school reaction (the Bouveault-Blanc reduction, in the case of esters), and if you don’t add the crown ether, that’s all you’re going to get. The researchers’ first experiences with the Birch reduction, attempting to reduce graphite to graphene, resulted in long set-up times and a small, but likely still smelly, ammonia leak, spurring them to try to simplify things. Birch thought of it as the Wooster / Godfrey Reduction because he based his work on their precedents. The largest one I ran was with ~2L of liquid ammonia in a 5L flask. By solving sodium in liquid ammonia, a sodium cation and a solvated electron are formed. To spit out such a characterization actually says more about you than me, especially when behind a pseudonym, and is counter productive. The reaction is named after the Australian chemist Arthur Birch. “liquified HCN, for example, which I’ve seen once and have no desire to encounter again”. https://www.scientificamerican.com/author/james-l-dye/. AAAS is a partner of HINARI, AGORA, OARE, CHORUS, CLOCKSS, CrossRef and COUNTER. Discount will be applied automatically at checkout. Please cite literature around the relative toxicities, that sort of experience does not provide real evidence. If you have an ACS member number, please enter it here so we can link this account to your membership. After workup I was rotovaping it down on the bench (all our rotovaps were on the bench… those were the days…!) What was the most critical supporting software for COBOL on IBM mainframes? Copyright © 2020 American Chemical Society. Can a half-fiend be a patron for a warlock? I used to run this one all the time in grad school (double carboxylate-to-bromide or carboxylate-to-iodide reactions were a mainstay on the way to various tortured small organics). Sign in with a different account. the funny thing, even carboxylates react with DCM, all it takes is a little base and a quaternary ammonium at reflux, and with unhindered aliphatic acids you get CH2(OCOR)2 AEGL-3 is the concentration when someone can suddenly collapse and die without help. A cold finger with dry ice/acetone is sufficient to cause the ammonia to condense into the reaction flask. Derek Lowe's commentary on drug discovery and the pharma industry. Lower molecular weight alkyl amines can be used in place of anhydrous ammonia for a birch reduction, if your just wanting to observe the blue colour this might be a more practicle alternative. Asking for help, clarification, or responding to other answers. This new paper (from a group at China Agricultural University) describes an ammonia-free (and indeed, amine-free) variant of the reaction – you use commercial sodium dispersion with a crown ether in isopropanol, and you can do it all at zero degrees C, as opposed to the -30 or so you have (at most) in liquid ammonia. I cannot recommend doing this H2S gas work of course, it was not safe, but imagine what would happen if you tried to release a quick stream of HCN gas in unventilated highschool lab. Here’s a bit more on them: https://www.chemistryworld.com/podcasts/solvated-electrons/2500348.article. To send an e-mail to multiple recipients, separate e-mail addresses with a comma, semicolon, or both. I gather you have other reasons to be averse to dichloromethane … “Chiracel column” springs to mind … . How exactly is an electron “solvated”? In the mid 1960s my colleagues and I used lithium in liquid ammonia to reduce an alpha, beta-unsaturated ketone to the lithium enolate of the corresponding saturated ketone. A novel protocol for a significantly improved, practical, and chemoselective ammonia-free Birch reduction mediated by bench-stable sodium dispersions and recoverable 15-crown-5 ether is reported. If electrons are in fact “solvated”, how do they give rise to the observed blue colour? What could Trump hope to gain from a *second* Georgia "recount"? Disposal is not an issue, as it is recovered and reused. It was subsequently determined that you need a trace of Na in your Li in order to get the reduction to go and that’s why you can buy Li + 0.5% Na from SIAL, et al. And condensing ammonia always seems like a magic trick, as the clear liquid just appears on the dry ice cold finger and drips down into the flask. That color (weirdly) is due to solvated free electrons, which means that this is one powerful reducing agent. I was reading that the ternary Na-K-Cs liquid alloy stays liquid down to -78C and can generate a stable radical anion from benzene, and only the Cs fraction of the alloy gets transferred into the Cs-benzenide. It was then that I realized that it was a good idea to make sure that all my valuables (like keys) were in my possession at all times (I had them but that was purely accidental) as we were evacuated….. Even a simple dry ice condenser is sufficient to do this, and the formation of the active reagent is easily observed by the appearance of the characteristic blue/green colour. And of all the gases that I’ve seen condensed on a cold finger, ammonia is definitely the one that I’d rather work with (as opposed to liquified HCN, for example, which I’ve seen once and have no desire to encounter again). The major difference is in the work up in that the Na/Silica can be filtered whereas the Na has to be carefully quenched…. NH3) that is easy to set up and not very moisture sensitive. Enjoy these benefits no matter which membership you pick. All Rights Reserved. I don’t remember. NH3 like global benzyl protecting group cleavage, some people do not even bother with condensing liq. By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy. I genuinely would like to be updated. To learn more, see our tips on writing great answers. This article has been sent to the following recipient: Sign up for C&EN's must-read weekly newsletter. PS My son popped home from university last night and had a grin on his face; seems that he had found “Things I won’t work with”. And nowhere near of your invented “1000x” more. Also your picture of the dissolved reducing metal/ ammonia solution shows a solution with a ton of free e-; it seems almost black instead of blue. The whole thing sheared off and started to flood the place with ammonia (crappy fumehoods didn’t help). The trick to make fine sodium particles by melting a chunk in boiling xylenes, stoppering the flask and giving some good shakes is described in Fieser, Organic Experiments as something to do in the undergrad lab. Hundreds of millions of pounds a year were circulated back when photo film was big. I thought the trialkyl substituted electron rich benzene in the substrate was to blame for the slow rate but now I realize maybe I used too pure lithium metal. By continuing to use this site you are agreeing to our COOKIE POLICY. > liquid H2S. 49 percent picked the U.S. Congress, 23 percent the IRS tax code.” Those days, it might be said, do come again and again. You get that same something-out-of-nothing effect when you do a distillation, of course, but I think it’s the lack of visibility of the source in the case of the ammonia tank that gives it more of a flourish.