Synth: Benzaldehyde

Polverone · Wed Apr 27, 2005 12:59 am

Clean your glass with a solution of sodium bisulfite, metabisulfite, or (possibly even cheaper and OTC) that Iron Out powder that's sold for removing rust stains. It removes manganese oxides quickly and easily.

bio · Working Bee

Great Polverone, good to know. Does it also take out permanganate stains?

No filtering ideas? It seems to either completely clog or pass thru any filter I tried. Decanting is OK and the settling is faster if the solution is degassed gently with vacuum. This degassing is very effective with most sludge type messes when they won't separate. Since I recovered the MnO2 didn't try cellite.

That extra high grade RA permanganate is some high dollar oxidizer so I can't bear to throw out the byproduct dioxide.

BTW ate some orange flavored cookies today called Polverones. Hmmm wonder what that means? Smile

Polverone · Wed Apr 27, 2005 8:04 am

Yes, it removes permanganate stains, at least from glass/plastics. I don't know how well it would do at cleaning off (say) skin. Iron Out itself is a mixture of sodium dithionite and metabisulfite. As its name implies, it can also remove stains from iron compounds, but it actually is more effective against manganese.

IndoleAmine · Dreamreader Deluxe

Thanks for the P2Pol info and tips on how to remove MnO2 stains, greatly appreciated.

Just wanted to mention that Na2S2O8 oxidations of toluene behave really strange, seen from a kinetic point of view ( Shocked

): a 5 mol persulfate oxidation of toluene seemed to run nicely, until the chemist decided to intetionally crank up the heat control from 65°C to 80°C after having added all the persulfate solution over the course of 2.5 hours (he really thought it would be a good idea). Result was a really incontrollable exothermic rxn that kicked in suddenly as a certain temp. threshold was reached, resulting in a giant "whooosh" sound and maybe 3-4 liters of boiling persulfate/toluene/MeOH/BzOH/BzCHO/water solution were shot to the ceiling in an arm-thick fountain,in a matter of 10-20 seconds (a 29/32 stopper was blown off too, and the fountain actually spit out of the condenser AND one side neck too - frightening when you consider the rxn vessel nominal volume of 5L..) Confused

--Conclusion: better partition the Na2S2O8 solution into two equal parts when doing large scale oxidations - since the rxn proceeds via an OH intermediate anyway, this means that you first make BzOH and then oxidize further to BzCHO in two steps. Also make sure to heat to at least 75°C BEFORE dripping in any oxidant. Hopefully the rxn can be controlled better this way...

(still tired from cleaning the huge, corrosive persulfate spillage that occured of course..)

Up to the next try..

i_a

Guest · Sat May 21, 2005 8:07 am

Yes, the ol, persulfat of Ammonia,

What Indole said is true, you must take care when bringing it up to heat, above 75'ish it just starts to go crazy,

SWIM had good results with a 60ml toluene batch,
I used copper sulfate, and Iron sulfate, as the catalysts to stop ring degradation,

I noticed from Nubee great post, that indeed amygdalin is present is lots of OTC Apricot, and almond cooking oils,

with simple hydrolysis this can transform into BzCHO,
This is something that is definately needs experimentation,
I wonder what the ideal conditions for hydrolysis are,

Something I have always wondered is the % yield of BzCHO from Mno2 & H2SO4,
As both chemicals are available OTC

SYn

Syn

left · Sun May 22, 2005 5:21 am

This sciencemadness thread seems to indicate they're pretty terrible.

IndoleAmine · Dreamreader Deluxe

Persulfate and toluene are at least as OTC as MnO2 and sulfuric IMO.

The prob with large-scale persulfate oxidations is/was the decomposition temp. of around 65-70°C for sodium persulfate (as can be read in the perborate/percarbonate review posted in the "Baeyer-Villiger" thread over in misc.stims, peroxide adducts of inorganic acid salts decompose at that temp. - d'oh...).

Just heat to 70-80°C, drip in half of the persulfate, let react for a while, then drip in the remainder, let react for a while (means 1-2h in each case). Use plenty of MeOH to avoid superheating due to layer formation and/or insufficient stirring (it can be recycled easily).

Yield is ~60 percent of theory calculated from toluene.

Glassware cleaned by rinsing with warm H2O.

Rocket science. Wink

bio · Working Bee

Hey Indole, glad you mentioned the geyser phenomena as good old neighbor Joe was about to dump in 5 kilos persulfate (slowly of course) for a first run which I told him would be very foolish for a learning experience.

With perborate there is an induction period and when heated to decomposition temp which most procedures call for the exotherm is definetly NOT proportional when scaled up. Once had a near geyser that was not predicted from 4 previous runs and then only doubling reactants again using proportional sized vessels. Man what a freakout that was. Exact same procedure and then after about an hour it went out of control and was half way up the reflux allihn with me holding the garden hose on the flask and damn the hotplate too. Really lucked out and actually lost very little out the top but amazingly the way this phenomena was ulimately controlled was to initially heat the mix hotter and faster in the beginning which prevented the all at once exotherm.

Speaking of the review article I was wondering if Na Perborate would work here, maybe with some catalytic sulfuric acid added? Any thoughts? Old Joe said he's got another 5Kg bucket of the stuff to use up!

At least in these parts persulfate is quite more expensive than perborate at least in the CP and RA grades. So have been looking for a persulfate electro regeneration procedure if anyone has one please post it. Also seems to me that the way to do this reaction is to do the regeneration either in situ ar in an auxiliary vessel during the main reaction.

frogfot · Tue Jun 28, 2005 4:21 pm

loki · guinea pig

scale is an issue with exothermic reactions, reduced in it's problematic nature by using a much larger flask than needed or a large flatbottom flask, which has a larger surface area per volume of liquid (more heat transfer, which is caused by a bigger surface area, means less instability of temperatures)

Bushroot · Sat Jul 02, 2005 4:06 pm

from what i found on hive archieves there are several ways to selectively oxidize benzyl alcohols to benzaldehydes -
- the air oxidation - PhCH2OH is refluxed 4-14 hours in DMSO and a stream of air is passed through the solution. The promised yield is more than 80%. I tried it, smells like a shit (air carries gases from apparatus) and after 6 hours the yield is no more than 30% after bisulfite purification of aldehyde.

- the K2Cr2O7 oxidation - they say it's quite effective, but as for selectivity - some benzoic acid is produced

- the HBr oxidation - claimed as da best. Yield 99% but i never met a person who tried it.

Please tell me which method is better!

proxy · Wed Aug 03, 2005 8:35 am

i was just reading this "scary" article on flavourings regarding Why McDonald's Fries Taste So Good... it mentions the following:

proxy · Wed Aug 03, 2005 9:05 am

also just found this United States Patent 4,716,249:

Process for preparing natural benzaldehyde and acetaldehyde

loki · guinea pig

so that's saying cinnamaldehyde, lecethin and a bit of plain old ordinary fatty esters, and some base, gives benzaldehyde AND acetaldehyde? I know BA was easy from cinammic acid but not acetaldehyde. Is that anything to do with the specific patent or is acetaldehyde a product of other routes of oxidising cinammaldehyde? all those fatty acids will make a nice surfactant known as 'soap' with a natural base (most natural of course being potassium hydroxide), and in the process one ends up with acetaldehyde. The gods of chemistry are handing it out on a silver platter it seems. Well for those inclined towards biochemistry anyway.

i presume the recovery involves forming the bisulphite adduct?

ultrabill · Fri Aug 12, 2005 9:50 am

What is the purpose of synthing benz if you can buy anywhere as oil of bitter almond or imitation almond?