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Organikum
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CycloKnight, I don´t understand why you use a not even insulated Vigreux in your steamdistillation setup as shown here:
http://www.sciencemadness.org/scipics/2cyclosteamdistillatio...
May it have some merits when you directly distill the formed benzaldehyde out albeit I doubt it when the cinnamaldehyde is added through a tube or
similar, but in a setup which is just steaming out a compound as in the first procedure the use of a Vigreux makes just no sense, it actually beats
the purpose.
In all my steamdistillations I used a as short way as any possible, only with a splashhead so necessary and also then I insulated everything up to
over the bend.
That makes it much quicker. IIRC benzaldehyde should come over with water in a ratio of 1:3 with forced steam even 1:1.
Besides this, thats great work, I will post a variation of it the next days.
/ORG
[Edited on 23-7-2006 by Organikum]
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Organikum
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Ok here we go:
- 800ml water
- 30g sodium carbonate
- 100ml synthetic cassia oil (which I hope to be basically pure cinnamaldehyde)
- 3,6g lecithin as surfactant
- some broken pieces of a clay pot as boiling stones
Now under reflux.
I use the one pot setup for I want to try in the second run to collect the formed acetaldehyde and for technical/equipment purposes.
Sorry no pictures I lent my camera to my girl.
The mixture took a yellow color and is boiling nicely. Foaming is not so bad, no splashhead needed. Dark blobs of oil are visible dancing around in
the brew what makes me think I could have added more lecithin.
Or maybe not. Steamdistillation produces excessive foaming even with addition of cooking oil (more oil?).
Distillate comes over containing at least 30% oil, which now at start looks and smells like benzaldehyde.
I wish I could push the distillation more - I am frigging tired. But it´s my own fault, a Erlenmeyer almost full is for sure not the right thing to
use. Jawn. Next time....
[Edited on 1-8-2006 by Organikum]
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Organikum
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And a question: As condensing actealdehyde is tedious wouldn´t bubbling the formed acetaldehyde into a solution of sodium bicarbonate form the
addition product? Would bubbling through ammonia water form acteldehyde ammonia? Would bubbling through a solution of hydroxylamine form the oxime?
Which of the three methods might be preferred/most practical?
Would be the formation of paraldehyde by bubbling the acetaldehyde into hot HCl/H2SO4 a viable option?
I will of course search myself for answers but I would also appreciate if somebody would be able to talk from experience.
regards
/ORG
Addon: Acetaldehyde ammonia would require anhydrous ammonia in ether as it seems and is therefor no real option.
[Edited on 31-7-2006 by Organikum]
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Organikum
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Another question: This article "The Oxidation of Cinnamaldehyde with Alkaline Hydrogen Peroxide.pdf" as requested by Wack and posted by Solo here, suggests that the addition of H2O2 transforms all cinnamaldehyde to either benzaldehyde or the epoxide which slowly degrades to benzaldehyde
itself. The article shows that after a very short time all cinnamaldehyde is transformed. Sadly I couldn´t find the actual reaction parameters,
something like "the necessary amounts of NaOH and H2O2 to reach the wanted conditions are added" doesn´t really help.
Anybody an idea how much H2O2 and NaOH to add and is the epoxide volantile with steam or not?
If not benzaldehyde could be distilled out of the reaction and the epoxide should degrade and so on.
Otherwise I couldn´t find how long it takes until all the epoxide is degraded. Maybe I just overlooked this on first sight.
This might be a nice alternative which would only require one steamdistillation if we are lucky without further separation.
Any ideas?
/ORG
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not_important
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I assume that by 'bicarbonate' you mean 'bisulfate' ? With a strong solution, yes. Same for hydroxylamine, it will go in water.
I'm thinking that the best optin might be catching it in some solvent. The solution might be directly usable for a desired reaction. Or if the solvent
choosen is inert enough, acid could be added to form paraldehyde or metaldehyde .
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Organikum
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Not bicarbonate nor bisulfate but sodium bisulfite of course. I apologize it was late last night.
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not_important
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And it was for me, I too meant bisulfite - the anion whose name can not be typed.
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Organikum
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Update on the running reaction:
After some hours I had to stop the steamdistillation for it got to late and I had to go to bed. The distillate which had come over - not very much -
was waterclear with a nice clear blob on the bottom. But the distillation seemed to have slowed down over time and I got the impression that only a
part of the cinnamaldehyde got converted into benzaldehyde and so I added some NaOH before restarting the steamdistillation this morning.
Much more distillate started to come over it is turbid, clear blobs at the bottom are slightly yellowish now.
So I ask myself: Does NaOH on the one side speed things up but on the other side produce a decent amount of sideproducts?
Or did I just fuck up something and if - what? Did the NaOH react with the frigging cooking oil I had to add to reduce foaming? Darn!
Suggestions for other anti-foaming agents? Paraffine/Stearine maybe? Or just some margarine or butter?
Addon: The yellow discoloration and the turbidity come most probably from mist (caused by the foaming) driven over. For I cannot fix this in this run
now I decided to ignore the issue, to drive the shit forcibly over and to do another steamdistillation on the product. Anything else would be endless.
In the next run I will obmit the splashhead and instead insert some glasswool into the Claisen which hopefully suffices as demister.
Addon2: Well sometimes I should listen to what I tell others and whats written in the basic literature 
A second batch is in steamdistillation and it runs quick and easy just from a 2l Erlenmeyer/Claisen/Liebig combo. No splashhead, no oil, no glasswool.
Ehem. Steamdistillation, as short way as possible as large diameter as possible. I guess a retort would be perfect. Or something like these irish
whiskey stills.
[Edited on 2-8-2006 by Organikum]
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Organikum
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First results from the cinnamaldehyde to benzaldehyde:
- It seems that the conversion was not more then 30% with sodium carbonate.
- Cinnamaldehyde is not easily steamdistilled without forced steam (whats not so bad as it is a easy means of separation)
- Too much lecithin causes excessive foaming and I am not sure if it is actually necessary in the sodium carbonate method as after my understanding
the amount of carbonate used is not mainly for basifying but for density adjustment)
/ORG
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not_important
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Spa supply might get you anti-foaming agents.
Why lecithin as a surfactant? It's a rather complex mix, and not all that stable. Would a low foam sulfonate serve?
Might the VO(AC)2 catalysed H2O2 oxidation of styrenes be useful? With yields in the 80% to 98% range, it would seem to be useful. It was listed in
this thread back in feb, I believe.
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Organikum
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Lecithin because I got it around the corner and it is named in the patent.
The sodium carbonate method was not so really successful. Now running the second method as described by CycloKnight and this looks better.
On an additional note:
I don´t think it is necessary to do a solvent extraction on the distillate, simple salting out the benzaldehyde/cinnamaldehyde should do. A saturated
solution of NaCl has a density of about 1,2 compared to about 1,05 of the oils, thats no problem.
/ORG
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CycloKnight
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| Quote: | | CycloKnight, I don´t understand why you use a not even insulated Vigreux in your steamdistillation setup as shown |
The reason is to increase the reflux rate. The rate of steam flow is very high; the stove heating the pressure cooker steam generator is at a maximum.
I reckon the steam is only in the column for about 2 seconds before reaching the condenser, therefore the reflux rate is actually extremely low.
Without forced steam however, it would be far better to use an insulated column or a very short column.
A couple points...
The steam distillation variation requires forced steam, there is no way boiling will produce sufficient steam without excessive foaming, in the
necessary time. Too long of a reaction time will destroy your product and turn it into tar.
Also, remember to check the pH now and again. The pH tends to drift - don't ask me why though !
I'm sure that adding vegetable oil will cause the oil to saponify, but I'm unclear how that will consume the alkali.
My experience is that the alkali is consumed somehow: either it is driven out by the steam or is is reacted in some way. In any case I've always found
it necessary to top up with NaOH when necessary (usually after several hours).
Using too much NaOH will produce instant benzaldehyde, but it will produce much tar and kill the efficiency. Its best to measure the pH and maintain
it between 12 & 13.
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hodges
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I managed to duplicate a good portion of this experiment on a smaller scale, although my attempt to purify the final product failed.
I reacted 0.3 moles of MnO2 with excess HCl in a hot water bath, leading the evolved Cl2 gas into NaOH solution for disposal. It was interesting to
watch the Cl2 bubbling into the NaOH solution, but the bubbles never making it to the top of the solution. They appeared to shrink with a jerky
motion. There was no smell of chlorine at all until I opened the flask after the reaction was complete. I filtered out a bit of remaining MnO2 and
then precipitated Mn(OH)2 using NaOH solution. I placed the precipitate in a 1 liter plastic bottle, where I washed it 10 times by filling the bottle
with water, allowing the precipitate to settle, then squeezing off the water. I then added H2SO4 (drain cleaner) slowly until all the precipitate
dissolved. At that point I discovered a small amount of MnO2 still remaining so I filtered that out. I dried solution in an oven. Unfortunately, I
had a slight excess of H2SO4, so when the MnSO4 was almost dry it started to fume. I decided to stop at that point, so I was not able to weigh the
MnSO4.
I added (NH4)2SO4 (which I had remaining from a reaction I did years ago between household ammonia and drain cleaner). The amount I added was just
under half the calculated mass of the MnSO4 (which I had been unable to weigh). I then added an appropriately scaled amount of water followed by
H2SO4. I ended up with a brown milky precipitate that looked very similar to the pictures previously posted in this thread.
Using small lead sheets left over from a battery experiment, I ran 2 amps of current through the solution for 5 hours. It quickly turned dark red. I
stirred occasionally, although I could see that the bubbles on the cathode were doing a pretty good job of stirring alone.
I poured the now-red solution into a flask and added 5ml of toluene. I placed this in hot water (around 50C). I let it react for about an hour,
occasionally stoppering the flask and shaking vigorously.
After an hour, I let the mixture settle. There was still some red color left but this all settled to the bottom, leaving a light yellow solution with
a darker yellow product on top. I carefully removed the product with a plastic pipette and placed it into another flask. I ended up with about 4ml
of product. The product smelled like cherries, although I could also still detect some toluene odor as well. When I let a drop of it sit in the air,
the toluene smell went away after about 20 minutes and the only remaining smell was of cherries. Of course, after a couple hours it started to smell
like benzoic acid.
So far, everything seems to have worked just as planned. Then I got the idea to try to purify the product by distillation, since I recently acquired
a cheap distiller with heating mantle from E-Bay. Since the distiller has a 500ml flask, I figured I would need more than the 4ml or so of product I
ended up with. So recharged the manganese compound by running current through it again. I repeated the process 5 more times over the course of a
week. I ended up with about 20ml of dark yellow liquid, which I washed twice with water. My plan was to distill this. I expected any remaining
toluene to come over at around 110, followed by benzaldehyde around 180. I was surprised when a clear liquid began distilling over at only 76
degrees. I was even more surprised when I was down to just a few ml of liquid left to distill and the temperature had only risen to 82. I didn't
distill the last few ml because I was afraid liquid condensing on the thermometer would drip down and break the flask since there was so little liquid
left at the bottom.
I can't figure out what I made. Obviously it was not benzaldehyde. It smells sort of like toluene. Given the very low boiling point I figured maybe
I had ended up with benzene. I tried burning a drop of it and it burns with an orange, sooty flame. But it did not freeze even at -20C, whereas
benzene should freeze around 5C. The product remaining in the distillation flask also does not smell like benzaldehyde. It has a foul odor, but
different from benzoic acid.
Presumably it is necessary to use a vacuum or steam distillation to purify benzaldehyde. But can anyone enlighten me as to what product I actually
got using regular distillation? I still have the product, as well as a ml or so of the original (pre-distillation) product.
Hodges
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not_important
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I'm guessing, based on you not mentioning drying the organics. The boiling point is a bit low for the toluene-water azeotrope, but not too far off.
Might be toluene-benzaldahyde-water. Water dissolves a bit in benzaldehyde, and slightly in toluene.
To generate benzene you'd oxidise all the way to benzoic acid and then decarboylate than, not really likely.
Try drying the liquid with (sodium or magnesium) sulfate; then measure the boiling point in a test tube, or try distilling again. And maybe pick up a
50 or 100 ml distilling flask, 500 is a little large for that amount of liquid.
Freezing points don't mean much unless you have a fairly pure compound, even a few percent of something else can greatly reduce the melting/freezing
point. Boiling oints have similar problems if the several componentes co-distill, which is what makes steam distillation work.
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hodges
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I tried drying and re-distilling the previously distilled product. I added several grams of anhydrous MgSO4 (dried in an oven), shook, waited 10
minutes, then poured off and re-distilled the liquid. It all distilled over at 76 degrees.
I took the re-distilled product and added some 3A molecular sieve to it. No significant heat appeared to be evolved. I poured off the liquid and
distilled a 3rd time. This time everything distilled over between 75 and 76 degrees. I added water to the molecular sieve I had used and it
immediately heated up noticably. So I'm pretty sure my product was dry.
I then tried distilling some "99% toluene" from the same bottle as I used for my original reactions. It all distilled over at 84 degrees. When I
distill pure water, it comes over at between 99 and 100 degrees so I know my thermometer is not far off.
Hodges
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not_important
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Well, toluene boils at 110.6 C, so you've a problem there. Benzene is 80.1, a bit low but care is needed when doing boiling points. If you're not
getting plenty of condensation on the thermometer bulb, or you are using it at the wrong immersion, the reading will be off. Try putting some of that
toluene in a tall test tube or smallish flask, heat it in a waterbath so that the organic boils but refluxs in the tube/flask (this means that the
water can't cover the upper portion of the tube). Stick the thermometer in so the bulb has condensed liquid running down it and take a reading.
Good job on checking for water and that your process had removed it, nicely methodical.
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hodges
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Thanks, not_important. I need to do some more measurements with my toluene. Since this is off the original topic, I will start another topic on
distillation in Beginnings (if one does not already exits) shortly.
Hodges
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2bob
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Benzaldehyde is produced by the following 'streckert oxidation':
Ca(OCl)2 Chlorination of Toluene [2]
"Toluene and dry Calcium Hypochlorite (bleaching powder) are heated together to 105°C in the abscence of other reagents. This avoids by-product
formation. If equal amtounts are used, volume-wise, there is a high conversion. If more bleaching powder is used, the conversion is more robust, but
contaminants such as benzal chloride and benzotrichloride are formed [...]"
http://designer-drugs.com/pte/12.162.180.114/dcd/chemistry/b...
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hell-fire
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As we all know benzaldehyde can be synthed from methylbenzene but what about dimethylbenzene? Methylbenzene is getting harder to find OTC and
dimethylbenzene is basically free for some people.
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not_important
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| Quote: | Originally posted by hell-fire
As we all know benzaldehyde can be synthed from methylbenzene but what about dimethylbenzene? Methylbenzene is getting harder to find OTC and
dimethylbenzene is basically free for some people. |
Not too easy - you need to chop off one of the methyls without affecting the other or also oxidising it just far enough, which as this thread shows
isn't easy.
I think the best solution to the problem is to slowly fractionate xylenes containg AlCl3 or AlBr3. Some intermolecular transalkylation occurs, giving
mono- and poly- methylbenzenes. The mono- is distilled off, using a good fractionating column, while the poly concentrates in the pot. After that it's
back to converting toluene.
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not_important
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This doesn't seem to have appeared before, and might be interesting. I was researching heteropolyacids for other reasons, and ran into the following
| Quote: |
Alkylarenes were catalytically and selectively oxidized to the corresponding benzylic acetates and carbonyl products by nitrate salts in acetic acid
in the presence of Keggin type molybdenum-based heteropolyacids, H(3+)(x)()PV(x)()Mo(12)(-)(x)()O(40) (x = 0-2). H(5)PV(2)Mo(10)O(40) was especially
effective. For methylarenes there was no over-oxidation to the carboxylic acid contrary to what was observed for nitric acid as oxidant. The
conversion to the aldehyde/ketone could be increased by the addition of water to the reaction mixture.
...
The ArCHR(*) and NO(2) radical species undergo heterocoupling to yield a benzylic nitrite, which undergoes hydrolysis or acetolysis and subsequent
reactions to yield benzylic acetates and corresponding aldehydes or ketones as final products. |
DOI: 10.1021/ja031710i
J Am Chem Soc. 2004 May 26;126(20):6356-62.
Oxidation of alkylarenes by nitrate catalyzed by polyoxophosphomolybdates: synthetic applications and mechanistic insights.
Khenkin AM, Neumann R.
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hell-fire
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I first thought about getting benzene from xylene then converting to benzyl chloride then using the benzyl chloride to synth benzaldehyde.
Here's some informaton i've put together thanks to rhodium and Vogel, this is nont my work.
Benzene.
Benzene can be obtained from dimethylbenzene by heating with AlCl3.
Synthesis of benzal chloride.
Into a 1-litre three-necked flask, equipped with a reflux (double surface) condenser, a mechanical stirrer (preferably of the Hershberg type, and a
gas lead-in tube extending to near the bottom of the flask, place 200 g (227 ml) of dry benzene, 20g of paraformaldehyde (40% Formalin may also be
used; the proportions are then 200g of benzene, 38g of 40% formalin and 50g of pulverized zinc chloride.) and 20 g of finely powdered anhydrous zinc
chloride. Support the flask on a water bath so arranged that the level of the water in it is about the same height as the reaction. Heat the bath to
60°C and pass in (through an intervening empty wash bottle) a rapid stream of hydrogen chloride until no more gas is absorbed (about 20 minutes):
allow to cool. Transfer the reaction mixture to a separatory funnel, wash it successively with two 50 ml. portions of cold water, two 50 ml. portions
of saturated sodium bicarbonate solution (It is essential to remove all the zinc salts in the washing process, otherwise the product largely
resinifies during the distillation.) and finally with 20 ml. of water. Dry with anhydrous calcium chloride or magnesium sulfate, and distill under
normal pressure from a Claisen flask with fractionating side arm until the temperature rises to 100-110°C. After cooling somewhat, distill under
reduced pressure and collect the benzyl chloride at 63-65°C at 12 mmHg. The yield is 70 g. Some (about 4 g.) p-xylylene dichloride, m.p. 100°, and a
small amount of diphenylmethane are present in the residue in the flask.
Synthesis of benzaldehyde.
Place 45 g. (43 ml.) of benzal chloride (Section IV,22), 250 ml. of water
and 75 g. of precipitated calcium carbonate (1) in a 500 ml. roundbottomed
flask fitted with a reflux condenser, and heat the mixture for
4 hours in an oil bath maintained at 130°. It is advantageous to pass
a current of carbon dioxide through the apparatus. Filter off the calcium
salts, and distil the filtrate in steam (Fig. //, 40, 1) until no more oil
passes over (2). Separate the benzaldehyde from the steam distillate by
two extractions with small volumes of ether, distil off most of the ether
on a water bath, and transfer the residual benzaldehyde to a wide-mouthed
bottle or flask. Add excess of a concentrated solution of sodium bisulphite
in portions with stirring or shaking : stopper the vessel and shake
vigorously until the odour of benzaldehyde can no longer be detected.
Filter the paste of the benzaldehyde bisulphite compound at the pump
and wash it with a little ether. Immediately transfer the bisulphite
compound to a separatory funnel and decompose it with a slight excess
of sodium carbonate solution. Extract the liberated benzaldehyde with
ether, wash the ethereal extract successively with sodium carbonate
solution and water, dry with anhydrous magnesium sulphate or calcium
chloride. Remove the ether on a water bath using the apparatus shown
in Fig. //, 13, 4, and distil the residue. Collect the benzaldehyde at
178-180°. The yield is 25 g.
Notes.
(1) A little iron powder or ferric benzoate can be used as a catalyst.
(2) If the clear filtrate in the flask is strongly acidified with concentrated hydrochloric
acid and then allowed to cool, benzoic acid (a by-product of the reaction)
separates in glistening plates. Filter at the pump, and recrystallise from hot water;
m.p. 121°.
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solo
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Since this is a very long thread and I haven't the time to read it all and at the risk of being redundant, ...................as I was researching I
ran into someone's study on gas phase production of benzaldehyde from toluene, I thought this might be of interest...............solo
http://www.faizkaskar.8k.com/p.html
It's better to die on your feet, than live on your knees....Emiliano Zapata.
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evil_lurker
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This should be looked at...
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi...
Unfortunatly I don't have access to this document, but according to wikipedia all you need is HBr, H2O2, Toluene, water, and a 40 watt light bulb to
crank out 80% yields of benzyl bromide.
And I can't think of the freaking patent to save my life, but I know it exists. You can oxidize the benzyl bromide with common sodium nitrate into
benzaldehyde.
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Polverone
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Here's the above paper.
Attachment: h2o2-radical-bromination.pdf (109kB)
This file has been downloaded 8015 times
PGP Key and corresponding e-mail address
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