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Author: Subject: toluene --> benzaldehyde
Ozone
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Hello,

Is the trick still to synthesize benzaldehyde from toluene? If it is, I have an oldey-but-goody that has worked well for me in the past.

To a chilled (ice) solution of toluene (or derivative, viz. p-nitrotoluene) and acetic anhydride (1:8 v/v) is added dropwise, sulfuric acid(conc). (~1:1.6 v/v on toluene) This solution is cooled to 0°C (ice). To this is slowly added (do not let the temperature exceed 10°C), with your safety glasses on, chromium trioxide in acetic anhydride (1:4.5 at 2:1 on toluene)--this solution must be prepared slowly and cold or it might run away from you-violently. This should take ~2hr.

What you should have is the benzaldehyde diacetate and a lot of green slop...and acid.

With my stuff I got crystals that I could filter off, then treat with 10% H2SO4 under reflux and then distill off under low vacuum.

The CrO3-AcO2-H2SO4 mixture is known as the Thiele (the same guy as the Thiele melting point apparatus) reagent, and the method I used was taken from

Fieser, L.F. and Fieser, M. (1967). Reagents for Organic Synthesis. John Wiley and Sons, Inc. ISBN 0-471-25875-X, pp. 146.

Undisputably one of the most useful texts arranged for the pragmatic organic chemist.

You can reduce any remaining chrome (VI) with sodium bisulfite (should be OK with the esters, not OK with your aldehyde, viz. in-situ, unless you wish to isolate the water soluble organosulfite, which can be recovered via acidic or alkaline hydrolysis). Do not put the waste down the drain. Chrome salts are nasty for both you and the environment.

I apologize in advance if this one has been previously posted, I checked most of the pages, but the topic was all over the place.

Cheers,

O3

-Anyone who never made a mistake never tried anything new.
--Albert Einstein
evil_lurker
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There is only one problem with that... in the USA its actually harder to get acetic anhydride than benzaldehyde.
Ozone
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Bummer. I can buy acetic anhydride without too much trouble, but, when buying benzaldehyde, I had to write the intended use and sign a form indicating that the chemical was specifically not to be used for the manufacture of drugs or weapons. My boss had to sign it too.

I was using it as a surrogate for phenylacetaldehyde, which was generated via strecker degradation from phenylalanine and glucose. This might be on some interest to someone who wants benzaldehyde.

cheers,

O3

-Anyone who never made a mistake never tried anything new.
--Albert Einstein
herbalextractions
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whats happened to all the pictures?
Hilski
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 Quote: Originally posted by herbalextractions whats happened to all the pictures?

I can still see them just fine.
Drunkguy
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I understand that the cassia oil method works because of a retro-aldol. I was just wondering if this only applies to the aldehyde or if the corresponding carboxylic acid can also be used? This is a variation of the Claisen (Ethylacetate + NaOEt + PhCHO), as covered in Vogel p1032. [I know Perkin, Knoevenagel, Reformatsky, Horner/Wadsworth-Emmons, Doebner etc all can be used to get the forward product, although it's a mute point in this post].

Also, on a more theoretical note, is there a way of reducing benzoic acid to PhCHO that is relatively OTC and does not call upon exotic reducing agents?

[Edited on 13-11-2006 by Drunkguy]
Mason_Grand_ANNdrews
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Great work Organicum, nice equipment setup. More there is
a way of reducing benzoic acid to benzene or the way from
sodium benzoate.

Benzene Extraction

When im thinking right, the "Gattermann-Koch" reaction is a
good replacement to make benzaldehyde from benzene
instead of toluenaldehyde. This should be easy with
anhydrous AlCl3 (Friedel-Crafts) to form the intermediate
formyl (C6H5-CHO) and then the aldehyde. I would guess
the synthesis should work when 78 g benzene is combined
with 14,8 g of anhydrous aluminium chloride and 7,5 g
anhydrous copper(II)chloride, the mix is careful heated a
while and then diluted with 500 ml 25% HCl. I dont
know the crude benzahldehyde can be removed from the
water by a simple distillation ? Might it must separated bevor
distilled above ~179 °C.
Drunkguy
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My only concern is that the reaction calls on CO(g), that and I dont know what the storage of AlCl3 is like for mothball projects (it's definately not otc).
Nicodem
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 Quote: Originally posted by Drunkguy Also, on a more theoretical note, is there a way of reducing benzoic acid to PhCHO that is relatively OTC and does not call upon exotic reducing agents?

It can be done trough "ketonization" with formic acid (which then becomes "aldehydation" ):
US4847424

Related patents:
US2053845
GB514452
GB382929 (uses Ca salts in a batch process)
GB190411747 (also Ca formates)
(there must be other related patents as well...)
chemoleo
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 Quote: I would guess the synthesis should work when 78 g benzene is combined with 14,8 g of anhydrous aluminium chloride and 7,5 g anhydrous copper(II)chloride, the mix is careful heated a while and then diluted with 500 ml 25% HCl. I dont know the crude benzahldehyde can be removed from the water by a simple distillation ? Might it must separated bevor distilled above ~179 °C.

Mr Mason, would you like to tell me where your extra carbon comes from?

I think I shall be watching your 'ideas' more closely in the future....

Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
Mason_Grand_ANNdrews
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I dont know the correct conditions to the synthesis. A rapidly stirrred
mixture should give the intermediate formyl in
the solution with the carbon monoxide content in the air
and the hydrochloric acid. This should be adequate, when
this not work bubble CO gas through the solution.
Not enough infos are available within the synthesis of
benzene if the formyl is formed by bubbling gently 1 mol of
CO gas into the solution after the HCl is added, the correct
temperatures or how long the synthesis need to complete the process.
I suppose a additional possibility is when the mixture of benzene/aluminium chloride/copper(II)chloride is
stirred between 6 - 10 °C, CO gas (air need longer reaction
time) is bubble into the mixture and over one hour the HCl is
dropped with a funnel into the solution.

[Edited on 20-11-2006 by Mason_Grand_ANNdrews]

[Edited on 20-11-2006 by Mason_Grand_ANNdrews]

[Edited on 21-11-2006 by Mason_Grand_ANNdrews]
Counter_Culture
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Any suggestions for salvaging acetaldehyde from the cassia oil to benzaldehyde synth when using steam distillation??

If the condenser and reciever are cool enough it would be in the water I assume.

Can they be seperated?
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benzaldehyde from toluene

toluene, water, sodium Chlorite *NaClO2*
reflux, then distill.

Yes, I do know that other compounds are made in the same mix.
but after it sits for a while, I do detect the smell of almonds from it.
Other compounds that may come from the reaction are:
BENZAL CHLORIDE
BENZOTRICHLORIDE
Benzyl Chloride
Nicodem
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Smell of almonds as a confirmation that you prepared benzaldehyde? You will get that smell even if the reaction mixture contains less than 1% benzaldehyde!
NaClO2 is a general reagent for the oxidation of aldehydes to carboxylic acids so what makes you believe it stops at the aldehyde stage? Have you analysed the product? Any references?
Organikum
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 Quote: Originally posted by Counter_Culture Any suggestions for salvaging acetaldehyde from the cassia oil to benzaldehyde synth when using steam distillation?? If the condenser and reciever are cool enough it would be in the water I assume. Can they be seperated?
In my rather unsuccessful tries to replicate the cassia oil to benzaldehyde synthesis I have not encountered the typical acetaldehyde smell nor have I been able to collect any distillate at the temperatures acetaldehyde is supposed to come over although the setup was rigged for exactly this purpose. Some benzaldehyde was formed, not very much but anyways.
Thats a bit disturbing as the acetaldehyde smell the same as benzaldehyde smell is already detectable when only traces of the compound are present. The lack of the smell was what alerted me first that something is going really wrong here.
I suspect the acetaldehyde undergoing condensation and that there must be actually some trick not pointed out in the patent to avoid this. US patens are horrible unrelieable if it comes to reproducing them. Well not only US patents, but they are worst IMHO.

[Edited on 13-1-2007 by Organikum]

Irgendwas is ja immer
womble
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overoxidisation & aldehyd'ation?

It can be done trough "ketonization" with formic acid (which then becomes "aldehydation" ):
US4847424

This is perhaps the most important patent I have noticed upon this topic. It even describes in some detail the production of the required catalyst(s). In addition to which, it does, somewhat unusually provide a level of detail on the actual reaction sequence.

I assume such a simple reaction should in fact work as well with catchetol based carboxylic acids?

If so, it would appear that the most productive, if not the most elegant route, would in fact be to proceed to over-oxidise past the desired product, without even attempting to stop the reaction, and then to use formic acid (albeit in massive quantities) to 'aldehyde'ise' the product.

The only problem I have is the sheer volume of THF that would be required to perform these reactions at any volume. Surely there must be an alternative solvent?
Rosco Bodine
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problem solved 102 years ago

There are a couple of patents that tell the tale .

Organikum cited this patent number on page 2 of this thread .

A nearly quantitative yield of benzaldehyde reported
by way of toluene oxidation by Mn(IV) sulfate ,
Mn(SO4)2 , manganese persulfate .....
no benzoic acid byproduct , but a small amount of tar ,
the benzaldehyde readily steam distills from the mixture .

The Bazlen patent US780404 is attached ,
see also the subsequent Bazlen patent US837777 .

Attachment: US780404 Manganic(IV) Sulfate electrolysis regenerated.pdf (173kB)
This file has been downloaded 2152 times

Hilski
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I wonder if the need for a diaphragm to efficiently produce the persulfate can be done away with if an anode/cathode size ratio of say 5:1 or higher is used. Basically, it would then be a war of attrition of sorts, as the anode with it's much larger surface area would oxidize the Mn(II) sulfate to the Mn(IV) sulfate faster than the small cathode could reduce it back to the Mn(II) sulfate.
Unless I have no idea what I'm talking about (which is likely) the cell would eventually contain a high percentage of the brown Mn persulfate, along with a small amount of the red Mn(II) sulfate.

\"They that can give up essential liberty
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deserve neither liberty nor safety. \"

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Rosco Bodine
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A porous cup around the cathode is unavoidable for this
persulfate because it is soluble in the acid , and therefore
it will be reduced at the cathode if it can contact it .

This should present no difficulty however , as the cathode
can be made of sheet lead formed into a cylinder which
sits immersed inside a clay flower pot filled three quarters full of sulfuric acid catholyte . If the lead sheet is cut into an L shape of proper dimensions , the long leg width is selected which will be just less than the depth of immersion in the catholyte , and it is rolled into a cylinder
shape around an olive bottle or similar sized form ,
leaving the short leg of the L shaped piece of sheet lead
as a riser and connection tab for the immersed cylinder .

If a 4 to 6 ounce glass bottle is used for the form for the cathode , it can be fitted with a two hole rubber stopper
at the top , and a rigid inlet tube nearly reaching the bottom inside the glass bottle , and a short rigid outlet tube reaching just below the stopper inside the bottle ,
so that cooling water may be run through to effect a
water cooled cathode . The flower pot can be suspended from polypropylene mesh netting , or
a suspension bridle can be made for it from polypropylene
cord or teflon insulated wire , so that the whole assembly
can be suspended from a ringstand , or from the center
of a support between two ringstands , one on either side
of the larger " bucket " or battery jar into which the
cathode assembly is lowered for electrolysis .

It would be easiest to manage this on a scale which
uses a 3 to 5 gallon black poly bucket for the anolyte
compartment . An overhead stirrer of adequate capacity
would be a good idea . However , if one of the larger
and heavy duty magnetic stirrers as are used for
fermenters and reactors is available , this could be used .
I would possibly put a glass or corelle dinner or salad plate in the bottom of a plastic bucket as a surface on which the stirbar would run , to prevent any long abrasion from the stirbar wearing a hole through the bottom of the bucket .....if it looked like abrasion there
could be a problem during long running .
Hilski
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I think I have all the stuff I need to try this on a smaller scale. If I am successful, I will take some photos and post the results here. Then maybe I can scale it up to a bucket size reactor, and try it again. It seems like the last time I went looking for a clay cup for an electrolytic cell that I had a hard time finding one without a drain hole in the bottom. I think that may be the only thing I don't have on hand, so as soon as I find one I can run the experiment.

\"They that can give up essential liberty
to obtain a little temporary safety
deserve neither liberty nor safety. \"

- Benjamin Franklin
Rosco Bodine
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Silicone of the sort that smells of acetic acid while it is
curing can be used to plug the hole in a flower pot .
I know it works for some of the milder sulfuric acid
electrolytes ....but I am not sure about how well it
would hold up to the stronger sulfuric used in this process .

Maybe check with a local ceramic shop and
see if they might provide an unglazed but
fired , coffee mug .

The flower pots that don't have the drain hole are
unusual , but can be found occasionally .....
and I don't recall what specialty of horticulture
is where they are used ....maybe bonsai ?

Also if it is more convenient , the anolyte and anode can be
inside the porous cup , and the cathode can be outside .
It isn't really of any importance what is the arrangement ,
so long as the porous cup , the flower pot , separates the two .

Those unglazed clay , terra cotta wine coolers don't have a drain hole IIRC , and you could probably use one of those as your porous cup .

[Edited on 27-1-2007 by Rosco Bodine]
womble
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boys and girls,

I think that maybe this might help..... It is one of hte lost PDF's from Rhodium's site and it deals specifically (in great detail) with what does and does not work in the oxidisation of toluene. VERY INTERESTING reading, highly recomended.

http://www.erowid.org/archive/rhodium/pdf/aromatic.aldehyde....

Appears that the best option for decent yeilds (toluene ain't so easy to get here as I can afford to waste it) would be to chlorinate the toluene:

Ca2(OCl)2 + 2C6H5CH3 => 2C6H5CH2Cl + ?

then either oxidise the benzyl halide or use caustic soda/potash to remove the halide and oxidise the alcohol?
womble
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although I do like this one, 20 seconds (MW) with silica doped with MnO2

http://www.erowid.org/archive/rhodium/pdf/mw.mno2.benzaldehy...

I assume that the silica gel would be laid out flat, the MnO2 on top of it. Allow it to set (or go off) and then grind it in a mortar t
Hilski
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Tyvek may be the ticket

 Quote: Those unglazed clay , terra cotta wine coolers don't have a drain hole IIRC , and you could probably use one of those as your porous cup .

I was looking around the house to see what I may have on hand that would make a good membrane, and I came across a huge stash of Tyvek chem suits I have had for a while. I haven't been able to find any hard data as to the pore sizes etc, but I have a sneaky suspicion that Tyvek may work as a membrane in this case. I know that water in the aqueous phase will not go through the material, so I assume that a solution saturated with MnSO4 and H2SO4 also will not penetrate the material. I searched around a bit and did find one patent that used Tyvek in a battery type electrolytic cell. I'm sure there are more, but this is the only one I have found so far:

Cathode cover for metal-air cell

Granted, this type of cell is not the same thing we are talking about, but it is similar. Another good thing about Tyvek is that it is made out of high density polyethylene (HDPE), so it will stand up to the harsh conditions created by the warm H2SO4. I have an idea for a small scale experiment, so I'll get to work on it soon and post results when I can.
Man I hope this stuff works.

\"They that can give up essential liberty
to obtain a little temporary safety
deserve neither liberty nor safety. \"

- Benjamin Franklin
roamingnome
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 Quote: I was looking around the house to see what I may have on hand that would make a good membrane, and I came across a huge stash of Tyvek chem suits

yeah i hate when i forget about my huge stash of goods.

i have used ammonia probes that use a PTFE (Teflon) tape as membrane so tyvex might be some good stuff.... but a envelope at the post office will be better then ripping up your suits dude!
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 Sciencemadness Discussion Board » Fundamentals » Organic Chemistry » toluene --> benzaldehyde Select A Forum Fundamentals   » Chemistry in General   » Organic Chemistry   » Reagents and Apparatus Acquisition   » Beginnings   » Responsible Practices   » Miscellaneous   » The Wiki Special topics   » Technochemistry   » Energetic Materials   » Biochemistry   » Radiochemistry   » Computational Models and Techniques   » Prepublication Non-chemistry   » Forum Matters   » Legal and Societal Issues