[Synnr01]

I have just started my undergrad project and it was left to me to order my chemicals. This was obviously a mistake as I have obtained solid, 95 % lithium diisopropylamide <this>.
I rather hastily assumed that purer = better, but unfortunately what I actually wanted was <LDA in THF/heptane/ethylbenzene>, which is considerably cheaper. Alternatively, as I now realise, I could have produced my own from BuLi and i-Pr₂NH.

Nevertheless, I have 25 g of this stuff and am hoping for advice on making the solution I need (the reaction I am doing is in THF).

Thanks muchly.

[Honclbrif]

Don't see what the problem is. Weight it out and use it like any other reagent.

[Vidya]

can you give us some more details of the project.

[Honclbrif]

I'll add a caveat: store it in a desiccator after you've opened it.

[Synnr01]

Well it's spontaneously flammable in air. And apparently such a strong base that it deprotonates and cleaves thf at above 0°C

[Synnr01]

I'm coupling two 5,5'-dimethyl-2,2'-bipy units, deprotonating with 1eq lda and coupling anions with 1eq dibromoethane.

[Honclbrif]

I was under the impression that LDA was used in part because it is non-pyrophoric. Looks like that's only true of the solution. I apologize for recommending something which could be unsafe.

Usually what I do when dealing with a reactive chemical, is to open the container, and immediately slap a septum on it, then secure the septum with a wire. Then you can cannulate a premeasured amount of solvent into the bottle. When you're not using it, put another septum upside down on top of the first to keep things sealed up.

[opsomath]

Do you have a glove box? That's the safest way to do it...I have never worked with this particular material as a solid though. Similar warnings are given for NaH, etc, though, which are actually safe to handle in air if you are cautious.

[fledarmus]

I have worked with solid LDA, although I find it is more trouble than it's worth. Since you have it, however...

The biggest issue I have with the solid LDA is that it sucks up water very rapidly, and LiOH usually isn't what I want to be adding to the reaction. If you've got a glove box, you're golden - weigh it out and dilute it in the glove box. If you don't, there are reasonably cheap (~$50) "glove bags" that can be used for the purpose (see for example http://www.sigmaaldrich.com/catalog/ProductDetail.do?lang=en&N4=Z530204|ALDRICH&N5=SEARCH_CONCAT_PNO|BRAND_KEY&F=SPEC).

If you have to work with it outside a glove box, it is pyrophoric but as others have noted, not nearly as bad as some other things like t-butyl lithium or solid sodium. Like I said, the worst problem is that it picks up water very quickly, so on muggy days you may end up with a lot of LiOH in your LDA. If you work under a nitrogen blanket (an inverted funnel connected to your nitrogen line works fairly well), you can transfer your material from the original container to a tared vial, cap it, weigh it, and then pour it into your dry solvent with a minimum of issues.

As Honclbrif said, store it in a desiccator or it will go bad very quickly.

[opsomath]

One thing I make sure to always do, once you make up a solution titrate it with menthol and bpy. A little googling should yield you a procedure for this, but basically you place a pre-weighed amount of menthol in a multi-neck flask under N2 with a little portion of bpy, then add your lithium reagent dropwise from a graduated syringe until you see a color change. That's the titration endpoint. Since you know the mass of menthol and it's a 1:1 reaction stoichiometry, you can calculate your LDA concentration from that.

[orgopete]

If this were my problem, I'd chalk up the solid LDA as a mistake and make a solution fresh. If you wish to use the solid LDA, I'd make a solution, e.g a THF/heptane/ethylbenzene?, from the entire bottle, titrate it, and carry on.

[herwiyanto25]

Dear colleagues,

It is very interesting topic relate about LDA. I have to do experiment with LDA suspension in mineral oil, however I have LDA chemical in hexane. How to substitute the solvent of LDA from hexane to mineral oil. Should I evaporate hexane first? I have already tried to evaporated hexane but the LDA solid could not use for next reaction. Does anyone could give me advices?
Thank you very much.

[mansigill1987]

LDA is commonly formed by treating a cooled (0 to −78 °C) tetrahydrofuran (THF) solution of diisopropylamine with n-butyllithium.

[discodermolide]

There is a better way, not involving BuLi.
Use Li metal, styrene, DIPEA in THF according to US patent Morrison, R. (1986). Stable LDA and method of preparation. US 4,595,779 priority 24/12/1984.

[NiceWeatherSunshine]

I make this fairly often with isoprene. It's better than styrene.

http://collum.chem.cornell.edu/documents/LDA_isoprene.pdf

The solid LDA needs to be kept under hivac for at least 6 hours to completely remove the DMEA. If you don't do that it will become insoluble (i have no idea why, just trust me and my group on this).

The recrystallization procedure on the website is bad, but the picture of the frit here is fine.
http://collum.chem.cornell.edu/documents/LDA_BuLi.pdf

this is how to recrystallize it:

vacuum transfer about 150 mL hexanes into a flask containing ~7g LDA (see the frit set up). Heat to 65C and (seriously) no warmer to dissolve the solid. Note: the LDA mixture will become transparent but occasionally not everything will dissolve. That's fine.  Once the LDA mixture is translucent remove it from the heat and filter the liquid through the frit into the other flask.  Transfer the LDA solution to another frit set up which has a medium of coarse frit, not fine. Slowly submerge the LDA solution in a dry ice/acetone bath (very slowly over a long period (1 to 1.5 hr)). The flask should be kept submerged untill all LDA is settled (it should be white, if not recrystallize again). Let the flask return to room temp and flip the frit. Evaporate the solvent. Wash the crystals: 10 ml of freshly distilled hexanes was added to LDA crystal to wash and the liquid was discarded. Washing was repeated twice. After removing the solvent, the whole system was put under full vacuum for 3-4 hrs. then put the entire frit in the glove box to transfer the solid LDA.