Sciencemadness Discussion Board

Simple Reactions with Fluorobenzoic Acid

DraconicAcid - 12-4-2023 at 13:10

So, at the end of the month, I'll have a chance to run some NMR spectra on my own samples.

I have some fluorobenzoic acid, and I want to get some spectra of fluorine-containing compounds to show my students the fluorine-coupling in 1H and 13C NMR.

I'd like to get more than one spectrum showing this- any suggestions for simple ways I can modify the molecule to make other interesting fluorine-containing things? Preferably in high yield- I don't want to waste the only fluorine-containing stuff I have.

I know I could nitrate it, or make the methyl ester. Alkylations on benzoic acid aren't great. I could decarboxylate it, but regular benzene is bad enough.

[Edited on 12-4-2023 by DraconicAcid]

SplendidAcylation - 12-4-2023 at 13:21

I think fluorobenzene is a lot safer than benzene! :)

You could turn it into the amide, using urea, and then perhaps dehydrate that to the nitrile.

clearly_not_atara - 13-4-2023 at 07:46

Benzene is quite carcinogenic; chlorobenzene shows only benign tumors when injected at the highest tolerable levels in rats. So more halogens does not always equal more dangerous. Searches for carcinogenicity assays of fluorobenzene turned up nothing.

Regardless, dry distillation with excess calcium acetate to hopefully acetylfluorobenzene paves the way to a number of interesting compounds without going through fluorobenzene or using forcing conditions to achieve direct electrophilic substitution. It should be possible to reduce the ketone without affecting the fluorine, one way or another.

SplendidAcylation - 16-4-2023 at 13:22

Quote: Originally posted by clearly_not_atara  
Benzene is quite carcinogenic; chlorobenzene shows only benign tumors when injected at the highest tolerable levels in rats. So more halogens does not always equal more dangerous. Searches for carcinogenicity assays of fluorobenzene turned up nothing.

Regardless, dry distillation with excess calcium acetate to hopefully acetylfluorobenzene paves the way to a number of interesting compounds without going through fluorobenzene or using forcing conditions to achieve direct electrophilic substitution. It should be possible to reduce the ketone without affecting the fluorine, one way or another.



Have you had luck with this sort of dry-distillation?
I am planning to attempt a similar thing using the iron powder method discussed in other threads.


P.S. why does it always say your posts were edited in 1969?
That was a good year, with Something In The Air by Thunderclap Newman released!

Dr.Bob - 16-4-2023 at 16:51

Can you reduce the acid to the benzoyl alcohol? Maybe make the amide or ester and try a aromatic substitution on the fluorine? Not real acitve, but might work. The amide to cyano sounds good also.

Sounds like a good challenge.

DraconicAcid - 16-4-2023 at 17:15

Quote: Originally posted by Dr.Bob  
Can you reduce the acid to the benzoyl alcohol? Maybe make the amide or ester and try a aromatic substitution on the fluorine? Not real acitve, but might work. The amide to cyano sounds good also.

Sounds like a good challenge.


Direct reduction of the acid is a no-go. I could make an ester and react that with a Grignard, though.

A substitution on the fluorine- as in a nucleophilic one? Then I wouldn't have a fluorine there for the NMR, so that would defeat the purpose.