Here’s a safety warning for my fellow synthetic organic chemists. Sodium hydride is considered corrosive to the skin or eyes due to the caustic byproducts of water reactions. I always had the safety seminar speakers (not always chemists!) Attacks SiO2 in glass. Bretherick is an indexed listing of actual hazards and warnings, with references. We have always used ethanol + a couple of drops (COUPLE!!!) Still, a common commercial packaging option for NaH is “in DMF-soluble bags”, meant for “just chuck the whole thing in” applications. 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. . Oh, never mind…. Using 60% sodium hydride dispersed on mineral oil is much safer than using pure sodium hydride. Let’s test dimsyl sodium then a popular strong base . 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). PLACE A DIRECT LINK ON YOUR DESKTOP!). Junior colleagues: talk to your more experienced senior colleagues before trying some chemistry that is new to you. Dimsyl anion can be a nice deuterating reagent. This OPRD paper has reawakened my awareness. Sodium hydride is a … 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. . tetramethylurea and dimethylimidazolone might be, Why would somebody heat a concentrated NaH solution without substrates in a close system? Sodium hydride is a severe irritant to skin and eyes. Sodium hydride is the chemical compound with the empirical formula NaH. You don’t want this. SODIUM HYDRIDE is a powerful reducing agent. And yeah, I’ve used that exact combination, too, many times. (2) Nitric acid plus alcohols, e.g., ethanol. Only a 15kpsi bursting strength?!? We switched to diglyme and told our contractor they were lucky to still have a lab. I was just figuring you were no longer welcome in New Hampshire…. 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. I have had no problems, but I don’t know if they exist or not. 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. Sodium hydride (NaH) reacts violently with water, liberating hydrogen gas . 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 case you’re wondering, that model ARC cell has an average burst limit of about 14,500 psi, which should inspire some serious thought. Is NMP a reasonable alternative solvent that does not have this issue? So… Sounds like you need a “Things I -might- work with” category. Just by saying “aprotic”, people shut down their mechanistic mind when thinking about possible side reactions (or explosions, in this case). Pure sodium hydride is prone to spontaneous ignition in moist air. For this reason, the most common form of sodium hydride used in labs is 60% sodium hydride dispersed on mineral oil. The hazards associated with the thermal instability of NaH/ DMF pose an even greater risk as the reaction scale increases. And even if you don’t, you can see those lively spikes in heat flow and appreciate what that’s going to mean if you have a decent-sized reaction going. The dangers of aryltrifluoromethyl Grignards are well described in an Org Syn prep: http://orgsyn.org/Content/pdfs/procedures/v82p0115.pdf. Very often, chemists think that some compounds or combinations are safe or inert, but that can be relative. Scaling up any such preparation, especially with heating, is a very bad idea. 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. . Ignites on contact with gaseous F2, Cl2, Br2, and I2 (the last at temperatures exceeding 100°C), especially in the presence of moisture, to form HF, HCl, HBr, and HI [Mellor 2:483 1946-47]. You are thinking about expansion at atmospheric pressure. Attacks SiO2 in glass. The problem is not NaH/DMF, but the high concentration and heating. Sodium hydride reacts violently with water to give NaOH which is a strong base and combustible gas, hydrogen. I realized what was happening, vented the setup, let it warm up safely, and started again with N2. You don’t usually need excess NaH and high temperature to does its job. Drug Repurposing: How Often Does It Work? Unfortunately, it does, but it is not as bad as DMF/DMA which is why I use it with THF. You can argue that DMSO was the intended substrate in this experiment. 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. When the process came back they’d swapped the solvent to DMF so they could significantly increase the concentration. When the $-cost of waste dispo went way up, departments started to segregate halogen waste from non-halogen waste. Spontaneous ignition in air can occur. 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.

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