Author Topic: Iodovanillin  (Read 4182 times)

0 Members and 1 Guest are viewing this topic.

pablos

  • Guest
Iodovanillin
« on: September 22, 2004, 12:27:00 PM »

http://www.sci.tamucc.edu/pals/morvant/orglab/orglab2/iodinationvanillin.pdf



Easy procedure scalable for the iodination of vanillin.

Captain_America

  • Guest
great!
« Reply #1 on: September 22, 2004, 06:17:00 PM »

pablos

  • Guest
shit timing
« Reply #2 on: September 22, 2004, 07:13:00 PM »
I would like to discovered this preparation 2 days ago,I have a bunch of shitti bromovanilline and I don´t know what to do with it. All the preparation are to long and I have no inert gas. What can I do with the bromovanilline except hydroxyvanilline?

Rhodium

  • Guest
Bromovanillin -> Syringaldehyde
« Reply #3 on: September 22, 2004, 08:14:00 PM »
Transformation of 5-bromovanillin into syringaldehyde
5-bromovanillin (5 mmol) is refluxed with EtOAc (3 mmol) and CuBr (1 mmol) in 5 M MeONa/MeOH (10 ml) for 14 h; classical work-up leads to pure syringaldehyde (95%).


Reference:

https://www.thevespiary.org/rhodium/Rhodium/chemistry/arylhalide.methanolysis.cu-etoac.html



Important details regarding this synthesis are discussed in this thread:

Post 275171

(uemura: "Re: Vanillin", Chemistry Discourse)


Inert atmosphere is not required:

Post 474077

(Rhodium: "Substituted Vanillins are Resistant to Oxidation", Methods Discourse)


Theroretical discussions:

Post 530151

(Kinetic: "Cu catalysed nucleophilic aromatic substitutions", Methods Discourse)

Post 528896

(Kinetic: "Bromination", Methods Discourse)



Saddam_Hussein

  • Guest
5-bromovanillin
« Reply #4 on: September 23, 2004, 03:57:00 AM »
Do a search for this specific compound on hest's name. He has posted a very simple yet effective method. (MeONa, a dash of CuX and DMF. Shake, boil and recrystallize  ;) )


Captain_America

  • Guest
Cu instead of Cu(I) salt
« Reply #5 on: September 23, 2004, 10:15:00 AM »
Pablos, if you are going to try this prep for syringaldehyde, try using activated copper instad of Cu(I)X as catalyst during the methoxide swap stage. Would also bee nice if you could report back.

From

Post 198873

(ZyGoat: "Re: Iodination of Vanillin", Chemistry Discourse)
I quote:

Example 3 was also repeated using from 5 to 10 mole % of cuprous oxide, cuprous chloride, cuprous iodide and copper dust, as the catalyst for conversion of the iodovanillin to hydroxyvanillin. Recovery of 5-hydroxyvanillin was 80-85% (remainder vanillin) with copper dust, from 70-80% with the copper oxide or salts.

They compare different Cu (I) salts as catalysts for the swap, but notice that it is optimal to use copper dust making it a bit more OTC. Use of activated copper* might bee lead to better results. Should work equally well or most probably even better with OMe than OH as the former is more powerful nucleophile.

*Active copper preparation:

An active copper powder can be prepared from copper sulfate. One hundred grams (0.4 mole) of copper sulfate (CuSO4·5H2O) is dissolved in 350 cc. of hot water in a 1-l. beaker. After cooling to room temperature 35 g. (0.53 gram atom) of zinc dust (more if necessary) is gradually added until the solution is decolorized. The precipitated copper is washed by decantation with water. Dilute hydrochloric acid (5 per cent) is added to the precipitate to remove the excess of the zinc, and agitation is continued until the escape of hydrogen ceases. The copper powder is filtered, washed with water, and kept in a moist condition in a carefully stoppered bottle.

Captain_America

  • Guest
Ok, Pablos, here is the story
« Reply #6 on: October 09, 2004, 04:39:00 AM »
Today I tried your method...

250 mL RB flask was charged with 5 g vanillin, 6.2 g KI and 100 mL MeOH and the resulting homogenous mixture was vigorously stirred.

60 mL household-toilet bleach (~5% NaOCl, product w/ pH ~12 is importnant, see the mechanism) was added to the reaction flask from an ordinary sep. funnel at such a rate that the addition took 20 minutes. No condenser/cooling were required as originally recommended since no temperature rise could be felt. Throughout the addition of NaOCl the colour in the flask changed from light yellow to deeply red and back to cloudy, coffee-with-milk coloured at the end of the addition. Some precipitate could bee seen at this stage.

The stirring was continued (cover the flask with foil to prevent MeOH evaporation) for 6 more hours after the addition was complete, (6 h is overkill but I had to leave to school).

Content of the RB flask was now transferred to a bigger 500 mL e-flask and ~150 mL 10% sodium dithionite was added, rinse the RB with it. [I didn’t had sodium thiosulfate, Nicodem suggests ascorbic acid, which is also cheap, OTC and works as good]. Then there was added ~150 mL 10% HCl, until the colour shifted back to light-yellow. Throughout the addition of HCl colour changes from yellow to deaply red and back to yellow, stop adding the HCl at when it turns yellow again. I felt it unnescessary to strip off the alcohol as originally suggested, maybee this affected my yield as the product is s a bit soluble in MeOH esp this volume, but not much more than in water so I didn't care. The neck of the Erlenmeyer was wrapped in foil, the flask sealed in a plastic bag (stinks SO2) and put in food-freezer for 40 minutes. In the meantime improvised vac-filtration setup was assembeled.

The thick, off-white precipitate was vac-filtered, washed with ~100 mL cold H2O and dried under a desktop lamp for 3.5-4 h. Dry, clean white crystals weighed 6.5 g (71 %). Interestingly, there was no smell of vanillin coming from this batch of crystals. Recrystallisation is not necessary but will be attempted from MeOH.

Comments:

The procedure is easy if you are in ghetto situation and gives very clean product; my yield went down the drain during the wash I think. Last time I iodinated vanillin I used the KI/I2/baking powder method, it is pretty messy compared to this, and in my hands it yielded the same as this. However I saved liquor phases from that synth becouse of need to regenrate iodine and I see now a a share of crystals have formed in those, so the yield is not too bad. I bet same holds here, but this time I didn’t save mother liquors. Noteworthy is that KI/I2 method give, even after the recrystallisation from MeOH, a tan product that smelled a bit vanillin. Pablos, this method is recommended, try it.

pablos

  • Guest
Same result
« Reply #7 on: October 09, 2004, 11:37:00 AM »
I tried it with quasi the same result, but a shorter rection time.
I have now the bromo and iodo vanillin and I fight vs a litre Race fluel. I posted my problem to the newbee forum.
Can look at it please?