Sciencemadness Discussion Board
Not logged in [Login ]
Go To Bottom

Printable Version  
Author: Subject: Bromovanillin Workup?
myristicinaldehyde
Hazard to Others
***




Posts: 166
Registered: 23-4-2016
Location: .͐͌ ͛҉̻̫̰̻̖E̮ͮ̐́̚ ̢̗̅̉ͩ͂̒̌.̯̻̺̯̀̎͂̄ͩ̚
Member Is Offline

Mood: сорок пять

[*] posted on 4-2-2018 at 11:28
Bromovanillin Workup?


I found a few procedures that claimed high yielding and quick bromination of phenols and phenol ethers using Oxone, NH4Br in wet methanol- a nicer alternative to using Br2 or HBr! However, I did not have any Oxone but instead boring old persulfate- I gave it a try anyway. I also used NaBr instead of the ammonia salt- NaBr is nicely soluble in the solvent anyway.

The biggest issue is the poor solubility of persulfate: however, if you reflux for 2h you have a mostly clear solution (persulfate gets consumed) The ammonium salt would be preferable.

My issue is isolating the bromovanillin- my first try I just dumped in an equal volume of ice water to the solution, which dissolved the small amount of solids remaining but gave a precipitate too fine to be caught by my filter paper. What little I could get (a gram at most), however, was very much bromovanillin.

Any suggestions for product isolation (other than use finer paper)? Does anyone have any experience with the selective crystallization of bromovanillin from vanillin?

some references:
oxone:

M. A. Kumar, C. N. Rohitha, S. J. Kulkarni, N. Narender, Synthesis, 2010, 1629-1632.
DOI: 10.1055/s-0029-1218723

N. Naresh, M. A. Kumar, M. M. Reddy, P. Swamy, J. B. Nanubolu, N. Narender, Synthesis, 2013, 45, 1497-1504.
DOI: 10.1055/s-0033-1338431

hbr/bro3
https://blogs.nvcc.edu/alchm/files/2016/05/46_vanillin.pdf


[Edited on 2018-2-4 by myristicinaldehyde]




If we don't study the mistakes of the future we're doomed to repeat them for the first time.
View user's profile View All Posts By User
Crowfjord
National Hazard
****




Posts: 390
Registered: 20-1-2013
Location: Pacific Northwest
Member Is Offline

Mood: Ever so slowly crystallizing...

[*] posted on 4-2-2018 at 15:49


Bromovanillin is pretty insoluble in water, while vanillin is fairly soluble. Dilution with water, filtration, and washing with water is typically all that is necessary. It seems persulfate doesn't work well under these conditions. Maybe try modifying the solvent or pH.

Have you read the bromination of vanillin without bromine thread ? I've had good success using the method given by DrNoisez in the third post, substituting the appropriate amount of 16% hydrogen peroxide. There is also an interesting method using sodium bromide and bleach.
View user's profile View All Posts By User
DraconicAcid
International Hazard
*****




Posts: 3404
Registered: 1-2-2013
Location: The tiniest college campus ever....
Member Is Offline

Mood: Semi-victorious.

[*] posted on 4-2-2018 at 16:31


If crystal size is the problem, then don't just dump in water. Maybe slowly add hot water to a hot solution until you get cloudiness, and then very slowly let it cool.



Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
View user's profile View All Posts By User

  Go To Top