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Author: Subject: Nitration of Vanillin with KNO3/H2SO4 in Acetic Acid
myristicinaldehyde
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[*] posted on 5-4-2018 at 11:55
Nitration of Vanillin with KNO3/H2SO4 in Acetic Acid


Nitration of Vanillin with KNO3/H2SO4 in Acetic Acid

Materials:
Vanillin (25mmol -> 3.8g)
KNO3 (30mmol -> 3.0g)
H2SO4 (25mmol -> ~2.5g)
Glacial acetic acid (this was not measured exactly- 30mL)

The sulfuric acid was diluted in glacial acetic acid (~10mL). This is exothermic.

Method:
To a roundbottom flask in a cool water bath with magnetic stirring was added 3g of potassium nitrate and 3.8g of vanillin, then ~30 mL acetic acid. The potassium nitrate will not dissolve much at first.
Dropwise addition of the sulfuric acid solution was started with the rate of a drop per second. The nitrate begins to dissolve and the solution takes on a dark red color. Towards the end of the reaction, a yellow precipitate is visible.

The contents of the flask were then dumped into ~150mL of cold water. After cooling the flask for 12h, the precipitate was gravity filtered and washed with cold water giving a crude yield of 4.5g 5-nitrovanillin.

Recrystallization was carried out with glacial acetic acid, which was not fun. The total yield of yellow crystal was 4.2g (85.3% yield). Using a thermometer and a tiny beaker on a otplate, the melting point was around the range of 170-175- there was a little smoke though. Either way, it is obviously not vanillin.

Future experiments with this product will be formation of the oxime and nitrile, and reduction to the amine (to be used for a diazotisation).

Overall it was a suprisingly easy reaction! The procedure is unreferenced. (I would greatly appreciate if anyone can verify my procedure also works for them!)





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weilawei
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[*] posted on 6-4-2018 at 08:22


Which position(s) do you think was nitrated? Very nice start all around!
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Boffis
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[*] posted on 6-4-2018 at 10:24


Yes, nice work. I suspect that the nitro group enters the 5 position.

Myristinaldehyde; roughly how much glacial acetic acid did you use for the crystallization?
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[*] posted on 6-4-2018 at 11:01


Quote: Originally posted by Boffis  
Yes, nice work. I suspect that the nitro group enters the 5 position.

Myristinaldehyde; roughly how much glacial acetic acid did you use for the crystallization?


I did this a bit back and my notes are terrible. It was around 40mL, which seems a bit large. I added warm water until I noticed cloudiness (didn't take much) and then put in the freezer. Hope that helps.




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