Attacks SiO2 in glass. But you’re not off the hook with DMF or DMA, either. Two more important hazards to be aware of in the “real” chem lab world: (1) Did you ever see a smoky vapor from acetone and CHCl3 and wonder what it is? NaH is representative of the saline hydrides, meaning it is a salt-like hydride, composed of Na+ and H− ions, in contrast to the more molecular hydrides such as borane, methane, ammonia and water. Do you have a reference for that? 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. This alkali metal hydride is primarily used as a strong, yet combustible base in organic synthesis. Sodium hydride is a severe irritant to skin and eyes. Call a doctor ASAP.” “If you fall into a giant vat of toluene, climb out, remove your clothing, get fresh air and call for assistance.” Worthless to a bench chemist. 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. Uh, I think you need to rethink that. The hydride anion is not free, but complexed, so it has reasonable steric bulk - enough for stereoselective reactions to occur. I am sure that this OPRD will be incorporated into the next edition. In the figure below, the alcohol shown is formed in Unfortunately, it does, but it is not as bad as DMF/DMA which is why I use it with THF. We had a gram scale alkoxide prep in THF as part of a macromolecular substitution process, and the scale-up was contracted out to someone with no proc dev experience. A traditional $\ce{S_{N}2}$ reaction takes place. But I did those reactions (for the most part) before I was aware of the possible hazards, and they have mostly been on a rather small scale and mostly at room temperature. https://www.elsevier.com/books/brethericks-handbook-of-reactive-chemical-hazards/urben/978-0-08-100971-0 (It might be available on-line through your institution. because they are NOT lazy and actually care about safety? Speaking of underappreciated safety concerns. For this reason, the most common form of sodium hydride used in labs is 60% sodium hydride dispersed on mineral oil. © 2020 American Association for the Advancement of Science. A traditional $\ce{S_{N}2}$ reaction takes place. https://en.wikipedia.org/wiki/Argon_compounds, https://pubs.acs.org/doi/full/10.1021/op900040y?src=recsys, http://orgsyn.org/Content/pdfs/procedures/v82p0115.pdf, https://www.elsevier.com/books/brethericks-handbook-of-reactive-chemical-hazards/urben/978-0-08-100971-0, https://en.wikipedia.org/wiki/Chlorobutanol, https://en.wikipedia.org/wiki/Bargellini_reaction. All reactions should be done under an inert atmosphere. Typo in my last post: “NH” should be “NaH”, of course. The non-preparative version can happen in a waste drum. https://en.wikipedia.org/wiki/Chlorobutanol. That’s why I never liked the distinction between “aprotic” and “protic” since several “aprotic” solvents are “protic” under the right reaction conditions. This is something I never thought of back when I was making Grignards of trifluoromethylphenyl derivatives. Bretherick is an indexed listing of actual hazards and warnings, with references. THF can be deprotonated to release ethylene (gas) and acetaldehyde enolate. An induction period of a radical reaction can be dangerous because the mixture does nothing until you turn your back on it. You need tougher lab equipment! Extremely violent detonation may occur if the solvent boils off, causing the Grignard reagent to solidify. The risks of “typically considered aprotic” solvents (a more appropriate name, IMO – with some effort you can make a whole lot of innocuous-looking substances to decide it’s time to give up some protons) in combination with sodium hydride are quite well known, especially to the industrial chemists. In this reaction it can be seen that sodium hydride behaves as a base. For an illustration of that, see the photo at right. The chemical reaction could be given as below – 2 Na + H2 → 2 NaH. 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. Senior colleagues: keep alert to potential hazards and do not dismiss junior colleagues who ask you questions or for your help when evaluating the safety and proper way to use some new chemistry. The hydride anion is not free, but complexed, so it has reasonable steric bulk - enough for stereoselective reactions to occur. It is THE most useful safety reference, IMO. I had this once (oil) but it wasn’t due to the NaH, but rather some very active lump of sodium which was in there; made a nice hole in the trespar bench. SODIUM HYDRIDE is a powerful reducing agent. 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). (Argon warning! All content is Derek’s own, and he does not in any way speak for his employer. 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. . And most definitely don’t heat them up! (2) Nitric acid plus alcohols, e.g., ethanol. You don’t usually need excess NaH and high temperature to does its job. Sodium hydride (NaH) is a strong base commonly used in organic chemistry to deprotonate alcohols, amine, amides, and other sufficiently acidic protons. alkali/alkaline earth metal hydrides such as sodium hydride (NaH) are also readily available chemicals, which are utilized almost exclusively as a strong Brønsted base for routine depro- tonation reactions in chemical synthesis (2,3 The Scheme 1B). The reaction is exothermic and self-propagating. You are thinking about expansion at atmospheric pressure. An exotherm from reaction of Na metal with boiling diglyme was what led to T2 explosion in Jacksonville. Now that’s a hell of a runaway if you ask me. An analysis of the gaseous byproducts from the DMF/NaH decomposition showed hydrogen, carbon monoxide, methane, and even ethylene/acetylene, which argues for a radical chain mechanism, at least in part. I have no proof, but I think that many decades of waste can geyser eruptions (or explosions) were improperly dismissed (even by Profs and senior PIs) as “Who knows?” or “Probably some free radical reaction.” and so on. In some cases the degradation gave curves with over 2000°C/min and nearly 10,000psi/min pressure changes! Let’s test dimsyl sodium then a popular strong base . You especially don’t want this when your reaction vessel is not contained within a large calorimeter, but is rather a Pyrex round-bottom in the middle of your fume hood. 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 . Only a 15kpsi bursting strength?!? Using 60% sodium hydride dispersed on mineral oil is much safer than using pure sodium hydride. So strongly consider alternative solvents or bases for such reactions, especially if you’re working on any kind of scale. The temperature where trouble hits is a little bit higher in those cases, but they’re trouble just the same. 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. 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. All reactions should be done under an inert atmosphere. The hazards associated with the thermal instability of NaH/ DMF pose an even greater risk as the reaction scale increases. Descriptively, CHCl3 anion (-)CCl3 adds 1,2 to the acetone ketone to give Cl3C–C(OH)(CH3)2, chloretone. Temperature to does its job metal and the hydrogen gas figuring you were no longer in. Give NaOH which is a radical reaction in which nitric oxide and nitrogen...., but it is the chemical reaction could be given as below – 2 Na + →. 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