GC_MS
(Hive Bee)
01-14-03 03:02
No 398057
      5-bromovanilline
(Rated as: excellent)
    

A couple of synthesis methods for 5-bromovanilline can be found on Rh's site as well as on the Hive collective using TFSE. However, there is one method which isn't "stressed" in the texts but has proven to be rather valuable in my syntheses.
Rh's original page: ../rhodium/chemistry /mmda.mescaline.html

A 250 mL RB flask was charged with 5 g vanilline (32.9 mmol) and dissolved in 50 mL glacial HOAc. The mixture was stirred with a magnetic stirbar. When all vanilline was dissolved, 2 x 1 mL bromine (39.0 mmol) was added with a 5 min interval. After one hour, 150 mL cold (4C) dH2O was added. The yellow-orange precipitate was filtered and the RB flask rinsed with another 50 mL cold dH2O, which was used to wash the precipitate as well. The precipitate was then washed with another 25 mL cold dH2O and dried to yield 7.5 g 5-bromovanilline (32.5 mmol) as a powder. Total yield: 98.7% Purity: 96% (via GC).

Voila, just to put the method into your attention. Pls be careful when handling bromine. It is a rather toxic substance...

Ave Hive, synthetisandi te salutant!
 
 
 
 
    Barium
(Hive Bee)
01-14-03 04:50
No 398065
      Nice! :-)     

Nice! smile

Catalytic hydrogenation freak
 
 
 
 
    Rhodium
(Chief Bee)
01-14-03 06:49
No 398082
      Added     

Thanks, I've added it to the above document. How did your Eugenol experiments go?
 
 
 
 
    GC_MS
(Hive Bee)
01-14-03 07:56
No 398095
      eugenol     


Thanks, I've added it to the above document. How did your Eugenol experiments go?




I'm still waiting for my heating mantle, necessary for vacuum distillations frown. Aside that, it seems a nice alternative, but only if you're hardcore. There is a need for alot of solvent to purify the product, and the yields are low. On the other hand, the required chemicals are cheap and unwatched.


Ave Hive, synthetisandi te salutant!
 
 
 
 
    GC_MS
(Hive Addict)
06-21-04 02:24
No 514574
      5-Bromovanillin purification tip for n00bs
(Rated as: good read)
    

I was in need of some 5-bromovanillin - a completely useless precursor *ahum* - and decided to scale up my usual procedure. I employed the GAA/bromine method for 0.5 mol vanillin. Addition of bromine was complete in 1.5 hours and reaction allowed to continue a further hour. Subsequently, some water was added and the precipitating reaction mixture stored in the fridge for a few hours. The precipitate was filtered (Buechner) and washed with water. We all know this story, n'est-ce pas?

However, my 5-bromovanillin didn't look very pure: dark yellow, at some points even orange. On a smaller scale, this wasn't really a problem because everything except vanillin and 5-bromovanillin was washed away. I could wash the product with a few liters of water though, but it wouldn't be very practical. Another alternative would be washing with aqueous methanol, but I decided to dissolve the whole crystalline mush in 500 ml methanol and bring it to a soft boiling. When all product was dissolved, heating was continued for about 2-3 min and 400 mL warm water (temperature shouldn't be higher than bp of methanol) was added (with stirring of the solution). This caused the precipitation of a white crystalline product. The reaction mixture was allowed to reach ambient temperature and transferred to the fridge (4C) to complete crystallization. The mixture was stored overnight, the precipitate filtered (suction) and washed with 200 ml of cold water. Total yield: 91% (based on dried weight of product).

The end product is a crystalline powder, very similar to vanillin itself in both appearance and odour. The colour is slightly off-white. The first crop of precipitate arising from the addition of water to the methanolic solution consists of a white crystalline powder. The second crop, coming forth from storing the reaction mixture in the fridge, consists of much longer needles. Using this procedure, a rather pure 5-bromovanillin can be obtained (GC-FID: 98% 5-bromovanillin, 1% vanillin). And most importantly, it looks pure wink. The look of my intermediary products is important as well, but we all know something is wrong with me, so don't worry if you happen not to care about it tongue.

There obviously is nothing special about this procedure (educated and self-made chemists use similar methods to find a good recrystallization solvent combination), but I thought it was a good addition for the few psychonauts with less knowledge about chemistry, but very hungry for M.

M!

I have a similar method for the recrystallization of 5-iodovanillin, but substituting MeOH for EtOH. It gives plates/needles.

Aztecunnilingus Maximus