Attacks SiO2 in glass. You don’t usually need excess NaH and high temperature to does its job. The preparation of sodium hydride includes a direct reaction between sodium metal and the hydrogen gas. Typo in my last post: “NH” should be “NaH”, of course. I realized what was happening, vented the setup, let it warm up safely, and started again with N2. Sodium hydride is considered corrosive to the skin or eyes due to the caustic byproducts of water reactions. NaH but still carried out their reactions at 100 °C.11 The researchers proposed that the active base in these reactions was sodium dimethylamine, resulting from the reaction of DMF with NaH. The left-hand panel is a Hastelloy accelerating-rate calorimetry (ARC) cell, before and after doing a DMSO/NaH run, and the right-hand panel shows the ARC apparatus itself after said assay. Severe explosions have been reported for over fifty years, as the new paper linked above details, but people still use these conditions without knowing that. The problem is not NaH/DMF, but the high concentration and heating. ), but a lot of academic and industrial synthetic chemists aren’t, or don’t realize how bad the problem is. I think you could get that ARC cell to burst under conditions of a steam-line rupture, water going from liquid to gas phase expands some 1700x, right? THF can be deprotonated to release ethylene (gas) and acetaldehyde enolate. In case you’re wondering, that model ARC cell has an average burst limit of about 14,500 psi, which should inspire some serious thought. The reaction had been run many times on a kilo scale without difficulties, but one day it got just a little too hot and took off. The dangers of aryltrifluoromethyl Grignards are well described in an Org Syn prep: http://orgsyn.org/Content/pdfs/procedures/v82p0115.pdf. If you know how to read a differential scanning calorimetry (DSC) plot, the one at right may well interest you. Whether or not you experience the second spike after the first will be a function of how large a reaction you have going, how well it’s mixed, and how much heat you can transfer out of it (and how quickly). Today, most labs segregate halogen waste from non-halogen waste but I will bet that, in the past, hundreds or thousands of exploding waste cans were caused by the acetone – CHCl3 exotherm. Sounds reasonable. Still, a common commercial packaging option for NaH is “in DMF-soluble bags”, meant for “just chuck the whole thing in” applications. You need tougher lab equipment! The reaction is exothermic and can lead to the hydrogen gas igniting. tetramethylurea and dimethylimidazolone might be, Why would somebody heat a concentrated NaH solution without substrates in a close system? Only a 15kpsi bursting strength?!? RT no reaction, somewhere at 80°C , boom but mild. I don’t know the answer because the Anntoine parameters I can find don’t even touch those temperature ranges…. Watch out for rapid expansion when you remove the LN2 bath! I prefer argon anyway, but the nerdiest among you will direct me to the wikipedia entry on “Argon Compounds” https://en.wikipedia.org/wiki/Argon_compounds . A traditional $\ce{S_{N}2}$ reaction takes place. This alkali metal hydride is primarily used as a strong, yet combustible base in organic synthesis. Per above I agree people need to openly discuss and review their experimental plans with others, especially as old timers often have awareness and experience (which unfortunately gets lost when they are let go or lucky to retire). Derek Lowe's commentary on drug discovery and the pharma industry. Also had managed to tell 2 Nobel prize winners to F off- he didn’t mange the 3rd -the head of department- as he thought the same about the other 2!). NaH is a colorless and white solid compound with a density of 1.4 g/mL, and a melting point of 800 degree Celsius. I am sure that this OPRD will be incorporated into the next edition. And here’s a variation: https://en.wikipedia.org/wiki/Bargellini_reaction. Bretherick is an indexed listing of actual hazards and warnings, with references. An editorially independent blog from the publishers of Science Translational Medicine. Most industrial process chemists are aware of these hazards (or should be! Though you will need to weld up the hole drilled in the bottom to prove there is no explosive filler inside…. Sodium hydride is stable in dry air at temperatures of up to 230 °C before ignition occurs; in moist air, however, the hydride rapidly decomposes, and if the material is a very fine powder, spontaneous ignition can occur as a result of the heat evolved from the hydrolysis reaction. Sodium hydride (NaH) reacts violently with water, liberating hydrogen gas (H2). (You can’t cleanly prepare acetaldehyde enolate from CH3CHO and strong base (e.g., LDA); elimination with sBuLi or tBuLi is one of the preparative methods.). Reacts … Spontaneous ignition in air can occur. But you’re not off the hook with DMF or DMA, either. We got handed a process with ~100 g of NaH in a limited vol of DMF at high temperature and we didn’t like the look of it. Descriptively, CHCl3 anion (-)CCl3 adds 1,2 to the acetone ketone to give Cl3C–C(OH)(CH3)2, chloretone. We switched to diglyme and told our contractor they were lucky to still have a lab. . . Very often, chemists think that some compounds or combinations are safe or inert, but that can be relative. It is an ionic … Ever see the paper about trifluoromethylphenyl grignard decomposition (https://pubs.acs.org/doi/full/10.1021/op900040y?src=recsys)? Sodium hydride reacts violently with water to give NaOH which is a strong base and combustible gas, hydrogen. This OPRD paper has reawakened my awareness. Further, the reaction between LAH and epoxides is quite facile, no doubt accelerated by the release of steric strain in the 3-membered epoxide ring system. Further, the reaction between LAH and epoxides is quite facile, no doubt accelerated by the release of steric strain in the 3-membered epoxide ring system. I’ve successfully used dimsyl anion from NaH/DMSO (research lab, not process lab) without any dismal results. In some cases the degradation gave curves with over 2000°C/min and nearly 10,000psi/min pressure changes! The hazards associated with the thermal instability of NaH/ DMF pose an even greater risk as the reaction scale increases. https://en.wikipedia.org/wiki/Chlorobutanol. The paper mentions a scale-up example using THF as co-solvent, actually. Properties of hydride sources. I get kind of nerdy and correct junior colleagues who sometimes refer to doing “reactions under an inert atmosphere” and mean dinitrogen (N2), but even N2 is not inert to some reactants or catalysts. Definitely was common in Process labs to consider risks and always had a Safety assessment before pilot plant operations (and work with skilled Engineers and EHS for added input). His recipe was to throw solid sodium metal onto undried DMSO- ON THE BENCH- and see the results, which happened to be a 10 foot jet of flame. We ran it at smaller scale to check and saw immediate and significant gas evolution before we added the substrate, with both dimethylamine and CO being identified. All reactions should be done under an inert atmosphere. Using 60% sodium hydride dispersed on mineral oil is much safer than using pure sodium hydride. AAAS is a partner of HINARI, AGORA, OARE, CHORUS, CLOCKSS, CrossRef and COUNTER. That reduced the likelihood of additional spontaneous chloretone syntheses. I learned that as a 2nd year: I watched as the liquid level rose in my flask even though I wasn’t doing anything yet. Bretherick calls that mixture “rocket fuel.” I have seen the aftermath of HNO3 – EtOH explosions that happened repeatedly in the same lab. Attacks SiO2 in glass. (Argon warning! . Sodium hydride (NaH) is a strong base commonly used in organic chemistry to deprotonate alcohols, amine, amides, and other sufficiently acidic protons. This was a loading of 4.5 grams of a mixture of 84% DMSO and 9.7% NaH (the rest was the mineral oil from the sodium hydride). The hydride anion is not free, but complexed, so it has reasonable steric bulk - enough for stereoselective reactions to occur. What temperature would you need to heat water to in a sealed system to generate 15000 psi? : if you ’ re trouble just the same industrial process chemists are aware of these hazards or. A DIRECT reaction between sodium metal and the hydrogen gas igniting any such preparation, especially heating! Boils off, causing the grignard reagent to solidify these hazards sodium hydride reactions or should be discovery. 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