[Chris28]

Hello everyone,

I think this could be a pretty long post, just so you know. But I would greatly appreciate all the help.

I'm a Master's student Bio-Engineering, and for my thesis I have to synthesize '15-crown-5 ' crown ether. I have been trying to do this in the laboratory for the past 4 months, without any decent yields. I am following an older protocol of Smid et al. Link: https://dx.doi.org/10.1021/ja00433a024 ---> page 5199 and 4'-formyl-15-benzo-crown-

It's been quite a disaster really. After numerous tries I've only managed to synthesize about 2 grams... As my background is more environmental sciences and not organic chemistry, I really could use some help also using this forum. The setup is a normal reflux setup in the beginning, and I use a rotavapor to evaporate the solvent. Then there is an extraction step (discussed below).

Is there something I'm missing in the protocol? Especially the extraction step (they talk about continuous extraction?) is a problem I think, I tried with a Soxhlet extraction but the oil seeped in the tubes. Also we just added the hot heptane to a beaker with the oil for extraction, is our extraction the biggest problem? (According to another paper by Sousa et al., file: https://dx.doi.org/10.3390/81200894).

I would need 10 + grams of this compound, so how it's going now it's not happening.

I am praying for help from people with experience in this, or people that could add anything to the protocol...

Thanks so much.

Christophe

mod edit, tidy links to papers

[hypervalent_iodine]

I said this in the other forum you posted in, but it sounds like you aren't using the right equipment for the extraction. You need either a bit of glassware suited for continuous liquid-liquid extraction (not a Soxhlet, this is for solids; also not sure what you mean by oil seeping into the tubes), or to do a normal liquid-liquid partition with a separatory funnel several times. The glassware, if you can get it, looks something like this:




It's not that common though I don't think, so it might prove difficult.

[wildfyr]

I agree with iodine. And the low tech answer is simply to use a sep funnel to do many (5+) extractions of the reaction with heptane. This could also be a recrystallization technique issue. Have you evaporated enough heptane off that the product is just barely soluble in the remaining solvent when its hot? Not doing this can lead to poor yields.

[kriggy]

But he is not doing liquid/liquid extraction but he should be extracting the product from oily residue. Friend of mine has similar problem few years ago and after he evaporeated the reaction mixture and had oily goo left in the flask, he just added a solvent, heat it to reflux, then remove the solvent and put new one. Repeat 20 times. AFter that, he just evaporated the solvent and got pure product.

[opsomath]

25 grams cost $169 on Sigma. I really don't know why you would be synthesizing this for a thesis in something that isn't chemistry. You order that, you are doing your actual experiments by the middle of next week.

[crawlingmcedge]

Is your thesis on a novel method for making crown ethers or something?

Why wouldn't you just buy off of sigma? Its dirt cheap.

4 months on just trying to make a cheap commercial product. Jesus.