The Hive => Methods Discourse => Topic started by: lutesium on July 20, 2004, 05:59:00 PM
Title: Using pyridine to hydroxylate the 5-br vanillin
Post by: lutesium 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 :( .!
Title: Cu/OH-
Post by: hest 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.
Title: hest: You're right to say that.
Post by: lutesium 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?
Title: concentrating
Post by: Vaaguh on July 22, 2004, 04:26:00 PM
You can always evaporate some of the H2O before extracting.