Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Malignoalfa on January 31, 2023, 03:27:22 AM
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synthesizing something I came across the following instruction:
"In a flask at room temperature (20-35 ° C.), 14.1 g (352 mmol) of NaH dispersed in mineral oil (200%) and 200 ml of DMSO were added."
I didn't understand this part:
"NaH dispersed in mineral oil (200%)"
would someone be kind enough to clarify for me?
thanks
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Its a special refined oil.
https://www.google.com/search?client=firefox-b-m&q=mineral+oil+200%25&oq=mineral+oil+200%25&aqs=heirloom-srp..0l3
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https://pubs.acs.org/doi/10.1021/ba-1957-0019.ch011
I can only give you a partial answer. NaH is sold in several forms, including as a dispersion in mineral oil that is 60% NaH by mass (it is safer to handle than dry NaH). I have only used it one time. When I did, I weighed out the appropriate mass and rinsed with pentane or petroleum ether to remove the oil, then I used it immediately. One has to adjust the mass weighed out based on the portion that is mineral oil. I do not understand the meaning of 200%.
EDT
I am concerned that NaH and DMSO together might constitute a hazard (see link below). Perhaps there is a different protocol that you could use.
https://pubs.acs.org/doi/10.1021/acs.oprd.9b00276
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Thanks for the reply. I'm sure mineral oil is just a safety product for NaH to stop being explosive. That is, it doesn't matter the amount of oil in the reaction, just add the correct mole amount of NaH. I think the 200% refers to 2 parts NaH to one part Oil.
Thanks.
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Thanks for the reply. I'm sure mineral oil is just a safety product for NaH to stop being explosive. That is, it doesn't matter the amount of oil in the reaction, just add the correct mole amount of NaH. I think the 200% refers to 2 parts NaH to one part Oil.
Thanks.
Could it be 20% dispersion in oil TYPO???? Why not just titrate the base following an established procedure if the protocol does not work???
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200% is not correct in any posssible way. Stupid or typo.
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Apologies for interrupting...
Experiments in 2019 have shown a degree of danger previously unknown from NaH in several solvents, especially DMSO. The sensitivity and the force of the explosion weren't suspected. Impressive pictures with less than 14g, rather 0.5g NaH.
pubs.acs.org (https://pubs.acs.org/doi/10.1021/acs.oprd.9b00276#) - science.org (https://www.science.org/content/blog-post/sodium-hydride-aprotic-solvents-look-out)
Older papers ignore it hence don't mention it. So be cautious.
I'm completely away from anything I believe to understand here, so I can be utterly wrong.
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"The hazards associated with the thermal decomposition of chemically incompatible sodium hydride solvent matrices are known, with reports from the 1960s detailing the inherent instability of NaH/dimethyl sulfoxide, NaH/N,N-dimethylformamide, and NaH/N,N-dimethylacetamide mixtures."
"The dangers associated with NaH/DMSO mixtures were evidenced by an explosion during the ARC analysis that was forceful enough to displace the ARC housing."
Enthalpy,
I mentioned this problem in an earlier comment, and I am glad that you are highlighting it.
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Thats scary, I have used g-quantities of NaH in DMSO and DMF, even heated it with a heating-gun... Whats the mechanism, is it red-ox or nucleophilic attack somehow? Free radical?