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For my high school senior chemistry project, I need to create and perform a lab. I've chosen to do the hydrogenation of 1-hexene with the catalyst of Raney nickel.

I'm struggling because I'm not exactly sure how to perform a hydrogenation. Some websites tell me I need nitrogen gas, some don't. I'm most likely performing a batch hydrogenation under atmospheric conditions.

Any advice on the actual procedure of the hydrogenation would be helpful.

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    $\begingroup$ Raney nickel, depending on the formulation, can be quite flammable and dangerous to work with, so given your experience, you may want to reconsider what you're designing here... $\endgroup$ – Zhe Jan 7 at 17:53
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    $\begingroup$ I've seen several fires caused by Raney Nickel waste, but then Pd on C can also cause fires. $\endgroup$ – Waylander Jan 7 at 18:25
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    $\begingroup$ You need an inert gas supply (Nitrogen), vacuum and a stirrer. Google "Balloon Hydrogenation" for detailed instructions. $\endgroup$ – Waylander Jan 7 at 18:52
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    $\begingroup$ What equipment have you got available to you? If you're going to do this, I hope it's in the school lab. I would consider the possibility of transfer hydrogenation using a hydrogen donor rather than hydrogen itself, given your limitations. Or, reconsider to use a homogeneous catalyst but these are usually much more expensive. $\endgroup$ – Beerhunter Jan 8 at 18:32
  • $\begingroup$ I am doing the lab in my school, but my main hurdle is that we don't have a vacuum. Is there any way to get around that? I can buy one but I need one that isn't absurdly expensive. $\endgroup$ – Alex Lee Jan 8 at 19:04
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To meet your brief of a) performing a hydrogenation and b) using Raney nickel, but performed in the safest manner, I would use aluminium-nickel alloy.

This is cheaper than sponge/Raney nickel and easier to handle i.e It's not pyrophoric until activated.

I would advise the use of nitrogen, but not a sweep as it can be detrimental to the procedure I'll outline.

I won't give molar details, but work on about 20% of alloy by mass vs your substrate to start with. I won't quote solvents either as I don't know if you need to isolate your hexane or not, nor how you intend to monitor the reaction. If you just need to do the reaction, go for a less volatile solvent.

To perform the hydrogenation itself, slowly and in a controlled manner with constant monitoring of temperature, add 4M NaOH. This reacts with the aluminium in the alloy to make Raney nickel. At the same time, hydrogen is generated which the nickel can adsorb and hydrogenate your substrate with.

Bear in mind that the NaOH solution introduces a lot of water, so if your solvent is immiscible with water, your stirring needs to be all the better.

You could use solvents that mix with a lot of water e.g. 1-butanol can contain up to ~20% water, but from which the bulk aqueous layer can be separated if needs be.

So long as the NaOH solution is added slowly enough, you can control the temperature. One way to manage is this is to only introduce 25% of your solution to be added at one time. That way if you accidentally add it all, it shouldn't go too crazy and boil/eject the contents uncontrollably.

Once complete, you can decant off the liquid but ensure you leave water behind to cover the catalyst. Rinse and decant until the pH is 8 or below. Then you have some options:

Dispose of the wet catalyst into bags that go off site from your school for disposal, using the appropriate school procedures or, Use dilute (1M) HCl to gradually deactivate the nickel. Again, add very slowly over hours if necessary. Then follow appropriate waste disposal guidelines for the nickel solution.

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