Sciencemadness Discussion Board

Advice with Hydroxyvanillin?

myristicinaldehyde - 25-4-2018 at 16:24

(Take a wild guess at what it will be used for)

I think I finally arrived at hydroxyvanillin, after a lot of pain and ethyl acetate. Here are some notes, and questions.

First I iodinated vanillin, with I2/KI/H20 and bicarbonate- which was the procedure used by Chemplayer. This worked very nicely.

The trouble was with the hydroxylation- I tried a few times with CuSO4 and Cu powder. I did not use amine ligands (I probably should) and I did not use DMSO (which probably would help the yield, but would swamp out the odor of the product, which makes the whole thing pointless...)

I eventually succeeded with 3.2g iodovanillin, 2g of CuSO4 petahydrate and 20.7g KOH (not reagent grade, but claims to be pure) in 100mL, with 7 hours of heavy heating. (A warning to use plenty of grease!) The reaction solution turns so yellow it is black, and the copper is deposited as a dark, heavy powder.

Failed trials (when I did not heat for long enough <6h or too little KOH) on acidification (I used sulfuric acid) dropped a pearly white ppt of what I assume is iodovanillin and vanillin. If minimal ppt forms, then the reaction will yield at least something.
The most annoying part was extraction with ethyl acetate (~20mL, x3) Addition causes small amounts fine greyish goop to form, which causes a bit of an emulsion. Filtering over celite would remove it, but I don't have celite. What is this material? How can it be prevented?

Distillation off of the ethyl acetate on a water bath left a red-black tar which happily crystallized/solidified to dark brown crystals (visible through the bottom of the flask) and a little tar. This all weighs 1.46g. Assuming it is pure hydroxyvanillin, it is a 77% yield. The literature does support this value (40-90%!) But it isn't pure, and I am unsure how to recrystallize my precious product.

Is there a way to stop the strange ppt problem during extraction? What solvent should be used to recrystalize it, or is it OK to push onwards to the next reaction?

The procedure was loosely based on the references provided by Reaxys. Identical conditions gave different researchers diferent yields, so I did not follow any strictly. I have attached the reaxys pdf.

Attachment: 3_4-DI~1.PDF (13kB)
This file has been downloaded 451 times

alking - 30-4-2018 at 13:50

Quote: Originally posted by myristicinaldehyde  
I did not use DMSO (which probably would help the yield, but would swamp out the odor of the product, which makes the whole thing pointless...)


What do you mean by this? "Swamp out the odor of the product?"

You can get what is essentially celite cheap and in bulk at a garden supply store, your local hardware store probably has it even, it is sold as 'diatomaceous earth.'

If it filters out a 'gray sludge' then it sounds like it might actually be filtering out some kind of particulate matter that is holding the emulsion together, if that is the case then that alone may solve your problem. If not, as you already suspect, you'll have to recrystallize it if not at least wash it and I can't help you there, I would just try different solvents/solvent systems. You should be able to get a good idea of the polarity/solubility pretty quickly and adjust from there.

[Edited on 30-4-2018 by alking]

PhenethylamineMachine - 1-5-2018 at 05:02

Not a topic I am comfortable discussing...

You can use C6H6 for re-crystallization.

the following link should help you out.

https://chemistry.mdma.ch/hiveboard/methods/000268713.html
Quote:

5-Hydroxyvanillin

2.8g 5-Iodovanillin, 1.6g hydrated CuSO4 and 76mL 4N NaOH were refluxed (105°) for 4.5h with continuous stirring under N2. After cooling to 60-70°, the mixture was filtered under suction and the residue washed with 3x10mL hot water. The alkaline solution was cooled to 10° and acidified to pH 3-4, by the dropwise addition of concentrated HCl. During this addition the mixture was stirred continuously and the tmperature maintained below 25°.

The resulting mixture, which contained a small amount of percipitate, was extracted continuously with ether for 16h. After being dried over anhydrous MgSO4, the ether was removed(60-65°) to leave 1.5g dark gray product. All but 0.10g was dissolved in hot benzene, from which, after concentration to 75mL, 1.15g 5-hydroxyvanillin crystallized, yield 68%, mp 128-129°. Recrystallization from benzene, with charcoaling, gave a chromatographically pure product, mp 133-134°; reported 132-134° by W.Bradley, R.Robinson and G.Schwarzenbach, J.Chem.Soc 793 (1930).

https://chemistry.mdma.ch/hiveboard/methods/000268713.html