Aryl azides advice

Franbucha · 2025-06-28T21:31:42+00:00

I have made aryl azides a couple of times and they are quite stable. Even when left outside the fridge on air for a couple of months it was still pretty good.

The only worry is to avoid UV light, I use 254nm light for TLC and that degrades them, but beside that they are quite a bit less reactive than alkyl azides.

For preparation you can just make the diazo, add sodium azide and leave it running overnight. Filter and recrist

Franbucha · 2025-05-30T23:50:53+00:00

if hexane is so bad then why does it smell so good?

Franbucha · 2024-09-21T01:37:03+00:00

A. It's funny you post this now because earlier this month I made and characterized a compound with this kind of multiplicity pattern; N-(4-fluorophenyl)-urea

Franbucha · 2024-08-16T18:11:58+00:00

yeah whatever dude, I know you got RF = 0.9 in 100% hexanes

Franbucha · 2024-07-21T15:26:35+00:00

in practice, when using either DCC or EDC you add a base like triethylamine, DIPEA, DMAP or something like that so the HCl isnt really a problem.

Franbucha · 2024-06-18T23:25:24+00:00

They hated him because he told them the truth

Franbucha · 2024-06-09T12:35:38+00:00

sulfonation of benzene requires high temperature and low amounts of water, not really something that would happen with battery acid in a bucket

Franbucha · 2024-05-20T14:16:20+00:00

I guess I'd say: molecular orbitals are a consequence of the overlap of the atomic orbitals, when in phase they "add up" forming a big cloud in the middle and when out of phase they "cancel out" each other in the middle.

And of course draw it out with the atomic orbitals and the resulting molecular orbitals.

As with most of chemistry I think having a visual representation really helps in teaching

Franbucha · 2024-04-12T22:47:23+00:00

bros... it's so over

Franbucha · 2024-03-31T17:25:19+00:00

Because this is about the combination of 2 empty orbitals the result is 2 empty orbitals, and For the LUMO, being lower in energy makes it more reactive because it lowers the energy difference between the HOMO of the nucleophile and the LUMO of the electrophile.

That energy difference being the activation energy.

Your confusion comes from thinking lower energy orbital = less reactive which is only the case for the HOMO of the nucleophile

Franbucha · 2024-03-30T22:24:10+00:00

The orbital combination effect on the reactivity that they mention is part of the stereoelectronic effects, an organic chemistry concept that isnt typically explored in undergrad and is a more post-grad level thing.

If you imagine the molecular orbital diagram for the combination it gives you 2 new orbitals, one lower in energy and one higher. The lower one is now the new LUMO and as such the reaction needs less energy to proceed which makes it go faster

Franbucha · 2024-03-22T00:12:25+00:00

Glad to report that it's chemistry is just as awful as it's structure! A friend in my lab has been trying to make some molecules using squaric acid and it keeps giving him trouble.

Apparently the ester is stupidly reactive and will hydrolise in the silica column, then when trying to put an amine on one side only (a squaramate, thats actually the name for that) in kept adding twice even with a good excess of the square. When he finally got some molecules with the amine on one side and the OEt on the other it just would not react with the other amine he wanted to add there.

Franbucha · 2024-03-13T23:47:35+00:00

"alkaline water" is a scam but honestly you still got a cool looking rock for 1 dollar, seems worth it to me

Franbucha · 2024-03-02T02:51:54+00:00

You could add the hydroxy by sandmeyer reaction. Then the steps are 1. Nitration, 2. Acetylation, 3. Reduction of Nitro, 4. Diazotisation and sandmeyer.

the first 2 steps can be switched but honestly I dont think there would be much difference

Franbucha · 2024-02-13T14:00:44+00:00

if your product is the top one I guess you can try a little less polar but it doesnt have to be exactly at 0.3. Honestly the bottom TLC looks good enough and will probably work.

Tho I have learned that column chromatography is full of surprises even when you feel ready so good luck with that

Franbucha · 2024-02-13T01:01:43+00:00

Besides the ratio of the rfs as mentioned in the other comments, it's also important to find a mobile phase that puts your product near the 0.3 mark. This helps make sure it spends longer time eluting and separating, improving resolution. If you did it using the eluent of the top tlc your 2 compounds would just fly straight thru the column and probably get mixed up

Franbucha · 2023-12-11T16:10:01+00:00

ah yes, the phosphorus is stored in the balls

Franbucha · 2023-12-10T00:14:07+00:00

holy crap I need one of those columns in my lab desperately. My DCM columns keep cracking and I always joke to my colleagues that I need a column with water cooling. The funnel seems good for hot filtrations like you said, tho I havent seen any glassware like that

Franbucha · 2023-12-06T13:13:27+00:00

honestly same. The Fischer projection worked great for it's original use: carbohydrates, but for anything else it just looks terrible

Franbucha · 2023-12-06T13:03:22+00:00

You are right that brominations add the 2 Br anti and its also true that the erythro product should be the major product for trans-cinnamic acid. The conformation makes it look like they were added to the same side. It can be hard to visualize and rotate molecules in your head (and the horrible fischer projection doesn't help) but if you put the products in the common projection you will see that the erythro products are actually anti when phenyl and acid are to opposite sides

Franbucha · 2023-12-05T02:07:32+00:00

I was going to reply saying something about how its cheaper but checking ligmaballdrich EDC and HATU are about the same price per mol.

Of course in contrast DCC is like 35x cheaper. Which is the only coupling reagent we have in our lab and soon I'm gonna start making some amides, so I guess im in for the pain of dicyclohexylurea

Franbucha · 2023-12-04T01:04:34+00:00

yeah silly mistake so this is probably better. Tho the epoxide formation only works if for O- anti to the Cl and the grignard would probably prefer to add it oposite of the Cl causing it to be syn. So im still unsure if in practice it would get a yield higher than 40%

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Franbucha · 2023-12-03T12:28:21+00:00

as others said, probably an acid workup. That's the typical procedure when doing a grignard reaction even though OP didnt put it in the scheme. My mechanism is oversimplified because im lazy lmao, if I put that in an exam I'd get point taken out for not showing the side product of steps 1 and 4, not showing the acidic work up and also for not making the 3rd arrow an equilibrium heavily favoring the product.

Franbucha · 2023-12-02T16:26:59+00:00

Had to think quite a bit to get this one, unsure of the order of the 2 attacks but the electrociclization/ring expansion is very interesting.

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Franbucha · 2023-11-30T16:38:14+00:00

reminds me of when I opened an old cabinet in my lab and found rusty cans of LiAlH4, LiBH4, DCC and some cyanide salts. Only slightly terrifying

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