Author Topic: Using pyridine to hydroxylate the 5-br vanillin  (Read 2332 times)

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  • Guest
Using pyridine to hydroxylate the 5-br vanillin
« on: July 20, 2004, 05:59:00 PM »
The idea is to lower the rxn times with an higher yield by useing pyridine for the hydroxylation of 5-br-vanillin.

I hope scravenging the halogen from the benzene ring via pyridine to form a cation which is open for the atttack of OH-

Swim added 15grms (n mole) of the aldehyde to 200mls H2O and trace of Cu powder (dunno why?).  Then he measured 8mls (>n mole) of pyridine and added it to the suspension. Visible rxn formed a grayish solution with a white preticipate. Then 18gms of NaOH was measured, dissolved in 80mls H2O and added to the rbf while still hot. A  visible rxn occured and the solution became orangeish. Then started refluxing under inert atmosphere. Still going on, planning for 3 hours.

Q. Can pyridine scravenge the 5- halogen and ease the attack of OH- ion?

Maybe using acetonitrile as a solvent, first refluxing the halo-ald. w/ pyridine then decomposing w/ OH- might be better?

Please help! I cant bear experimenting for days without any referenced mechanism and real result :( .!


  • Guest
« Reply #1 on: July 21, 2004, 03:33:00 AM »

Use Cu (salt or metal) and NaOH. and use your time to optimise something with a low yeald.


  • Guest
hest: You're right to say that.
« Reply #2 on: July 21, 2004, 09:21:00 AM »
hest: You're right to say that. The Cu method is easy and high yielding. But I dislike refluxing 2 litres of H2O for 30 hours and trying to extract the HUGE rxn mixture. I just think that its impractical. But yes, its high yielding.
I still wonder if pryidine can cleave that Br?


  • Guest
« Reply #3 on: July 22, 2004, 04:26:00 PM »
You can always evaporate some of the H2O before extracting.