Antoncho (Official Hive Translator)
08-30-01 21:01
No 208702
      The easiest synth of benzaldehyde from toluene     

Ladies and gentlemen!

This is from our Russian chemforum, by courtesy of Babayka.

Having done a quick search, i found that there once was an inquiry of this synthesis on the Hive, unfortunately, no info was found at that time and the project was disregarded.

IMHO, it is the coolest synth of benzaldehyde there ever was. The description is not as detailed as it could bee but all the important points are here.

Synthesis of benzaldehydes from toluene and its derivatives. (note that obviously substituded toluenes may bee used too)
...Synthesis of benzaldehyde and its derivatives by oxidation of the corresponding toluenes is an important industrial process in pharmaceutic drug synthesis.
Oxidation of -CH3 group to -CHO is carried w/MnO2 in presense of sulfuric acid. In case if MnO2 is present in excess, aqueous acid is used and if a stoichometric quantity of MnO2 is taken, conc. H2SO4 is emloyed.
If the rxn is carried out at temp's below 40 C, aldehydes are formed, however, if its temp's allowed to rise to 60-70 C, the main product is benzoic acid.


(Chief Bee)
08-30-01 21:23
No 208703
      Re: The easiest synth of benzaldehyde from toluene     

This is true. However, for good yields a special form of activated MnO2 must be used (finely divided), but I have no exact prep details.
08-30-01 21:57
No 208717
      Re: The easiest synth of benzaldehyde from toluene     

maybe ref to "Transactions of the Faraday Soceity"-
just remember it from the past. nothing specific.

always appreciate your time and consideration
(Stoni's sexual toy)
08-30-01 22:02
No 208719
      Re: The easiest synth of benzaldehyde from toluene
(Rated as: excellent)

I got a better one laugh

toluene ----> benzaldehyde in 95%


Ferrous-Copper Catalyst: Toluene (7.6 g.), water (35 ml.), ferrous sulphate (0.110 g.) heptahydrate, cupric acetate (0.072 g.) and methanol (8 ml.) are placed in a 250 ml. reactor.

Sodium persulphate (47.05 g.) in an aqueous-methanol solution of sodium persulphate is added slowly to the mixture which is maintained at C., in an atmosphere of nitrogen and under agitation.

The organic phase is separated after two hours and the aqueous phase is extracted with ethyl ether.

The combined organic phases are distilled to afford 8.29 g. (95% yield) of very pure benzaldehyde (compared against a pure sample).

US-Pat 4,146,582
(Hive Addict)
08-31-01 00:22
No 208778
      Re: The easiest synth of benzaldehyde from toluene     

can oxone be used in place of the persulfate?  what about a solution of caro's acid? (yes, that's extreme- just asking though)

(Master Searcher)
08-31-01 00:29
No 208782
      Re: The easiest synth of benzaldehyde from toluene     

Here's a list of related patents: 

Patent US613460
Patent US650332
Patent US661872
Patent US677239
Patent US698355
Patent US780404
08-31-01 07:03
No 208886
      Re: The easiest synth of benzaldehyde from toluene     

NICE Osmium!

Go Ugly Early
(Distinctive Doe)
11-27-01 23:26
No 241349
      benzaldehyde from toluene - Additions     

Cerium-catalyzed selective oxidation of alkylbenzenes with bromate salts.    
Ganin, Eyal; Amer, Ibrahim   
Synth. Commun.  (1995),  25(20),  3149-54.

Ce(IV) NH4NO3 (CAN)-catalyzed oxidn. of alkyl aroms. with KBrO3 affords aldehydes, ketones, carboxylic acids or alcs. in varying yields depending upon reaction conditions and substrate.  E.g., 4-MeC6H4Me is treated with CAN and KBrO3 in 1,4-dioxane/water soln. to give 4-MeC6H4CHO in 70% and 4-MeC6H4CO2H in 20%.

Do Your Part To Win The War
(Hive Bee)
11-28-01 01:38
No 241403
      Re: benzaldehyde from toluene - Additions     

Foxy, will that work for PAA from ethylbenzene?
11-28-01 17:02
No 241641
      Re: benzaldehyde from toluene - Additions     

>will that work for PAA from ethylbenzene?

Probably not, these oxidations are specific for benzylic position (not terminal), so acetphenone will be formed.
09-04-02 04:47
No 352445
      I was wondering if anyone has had any success ...     

I was wondering if anyone has had any success with the following method posted by antoncho previously, and if anyone has any idea on the MnO2 preparation.

It seems to me that it shouldn't be that hard to come up with other methods with fairly easy precursors.
I'm hoping to get my hands on some stuff in the near future to give this a go.

Synthesis of benzaldehydes from toluene and its derivatives. (note that obviously substituded toluenes may bee used too)
...Synthesis of benzaldehyde and its derivatives by oxidation of the corresponding toluenes is an important industrial process in pharmaceutic drug synthesis.
Oxidation of -CH3 group to -CHO is carried w/MnO2 in presense of sulfuric acid. In case if MnO2 is present in excess, aqueous acid is used and if a stoichometric quantity of MnO2 is taken, conc. H2SO4 is emloyed.
If the rxn is carried out at temp's below 40 C, aldehydes are formed, however, if its temp's allowed to rise to 60-70 C, the main product is benzoic acid.
(Hive Bee)
09-04-02 07:20
No 352497
      Activated MnO2     

If you had typed 'MnO2' in the FSE you would have found:
Post 296395 (hest: "You need 'activated' MnO2.", Newbee Forum) (from MnCl2).
(I could have just said UTFSE but since I'm thinking of risking all good karma by asking a MBRP related question at Stimulants it would feel hypocritical)

MnO2 can also be prepared from MnSO4 as described in later versions of Vogel (not 3rd).
(Might look it up and post it to make up for an anticipated karma loss..)

Mountain Boy
(Hive Bee)
09-04-02 07:41
No 352508
      activated MnO2     

Preparation of activated Manganese Dioxide at the bottom of this doc.

../rhodium /oxycodone.html
(Hive Bee)
09-07-02 18:40
No 353845
      Give me the details     

In case if MnO2 is present in excess, aqueous acid is used and if a stoichometric quantity of MnO2 is taken, conc. H2SO4 is emloyed.
If the rxn is carried out at temp's below 40 C, aldehydes are formed.

Is this solventless?
What is stoichometric?
How much H2SO4 is used in both stoichometric and in excess reactions?
In what ratio is MnO2 : Toluene reacted to get the best yields?
What are the ratios for the stoichometric and excess reactions? 
What are the yields?
Where can I find information about this synt?

Please I'm very interrasted in this synt. I really thankful for the person with the answers. frown

(Chief Bee)
09-07-02 19:11
No 353850
      Introduction to stoichometry: http://www.     

Introduction to stoichometry:

You can find a procedure by using either or one of the patent search engines suggested on TFSE page.
(Hive Bee)
09-08-02 12:03
No 354256

93 g Toluene + 87 g MnO2 + ? g aq H2SO4 ---> 106 g Benzaldehyde.

Is this without a solvent and how much H2SO4 is used? Must the reaction have a specific PH?
(Chief Bee)
09-08-02 18:32
No 354314
      General Method for the Preparation of ...
(Rated as: excellent)

General Method for the Preparation of Benzaldehydes
J. Med. Chem. 27, 1111-1118 (1984)

Activated MnO2 (21.7 g, 0.25 mol) and 200 mL of benzene were refluxed for 2 h in a Dean-Stark apparatus. Then the benzyl alcohol (0.05 mol) was added and the solution was refluxed for 24 h. The reaction mixture was filtered and the solvent was removed. The residue was recrystallized in methanol/ether or acetonitrile to afford the pure benzaldehyde.

General Method for the Preparation of Benzaldehydes
JACS 77, 4399-44901 (1955)

A solution of 10.9 g (0.1 mol) of benzyl alcohol in 1000ml of solvent (1) was stirred at room temperature with 100g of manganese dioxide. When the reaction was over (2), the solution was filtered. The solid was washed with chloroform and ethanol and the washings were added to the original filtrate, the solvent evaporated and the residue distilled to give the benzaldehyde.

(1) CHCl3, DCM, Et2O and petroleum ether are all okay, with little difference in yield.
(2) After one hour, the yields are 55-70% and after 24h 75-90% depending on the benzaldehyde.
(Hive Bee)
09-08-02 22:27
No 354361
(Rated as: excellent)

SWiM has a nice collection of books, viz Meyer's Synthese der Kohlenstoffverbindungen. It's a collection of prepartion methods, described very shortly, with references to the original publications. Here are the data for benzaldehyde:

1) 100 g benzene + 45 g AlCl3, HCl, 40-50c + CO for several hours. Pressure is 90 atm. Yield: 30 g --- 100 g AlCl3, 1 g TiCl4, 190 g benzene, 30-40C + CO till 60 atm. [1,2]
2) 60 g benzene, 60 g AlBr3, 12 g CuCl2 + CO, HCl (2:1), first cool down with water, then 5h at 20C. Yield: 90%. Or with AlCl3, Cu2Cl2, 7 hours at 45C + CO, HCl [3,4]
3) 4 mol benzene, 1 mol Ni-carbonyl, 4 mol AlCl3, stand for several days. Add water. Yield: 20% [5].
4) 150 g benzene, 90 g Hg 43-45C in 40 min + 120 g AlCl3, 15 g AlCl3 + 6 H2O, 15 g Al(OH)3. Stand for 3h. Yield: 68% oxime + 1.2 g aldehyde [6].
5) PhMgBr, ether + HCOOH or 3 mol formic acid ester -50C. Better is + 1/2 eqv ortho-formic acid. Yield: 93% [7,8,9].
6) 6 g PhMgBr, ether, 2 g methylcarbylamine, ether 0C stand for 12 hours. Or + methylformanilide, or + ethoxymethyleneaniline, boil shortly. Yield: 46% [10,11,12].
7) benzene, HCl, HCN, AlCl3, 100C [13].


1 DRP 281212
2 EP 334009
3 GATTERMANN, Ann 347 (1906) 351
4 HEY, J Chem Soc London (1935) 72
5 DEWAR, JONES, J Chem Soc London 85 (1904) 213
6 SCHOLL, Ber 32 (1899) 3498
7 ZELINSKY, Chem Ztg 28 (1904) 304
8 GATTERMANN, MAFFEZZOLI, Ber 36 (1903) 4152
9 WOOD, COMLEY, J Chem Soc Ind 42 (1923) 429
10 SACHS, LOEVY, Ber 37 (1904) 875
11 BOUVEAULT, Bull Soc Chim France (3) 31 (1904) 1327
12 MONIER, WILLIAMS, J Chem Soc London 89 (1906) 275
13 HINKEL, AYLING, J Chem Soc London (1932) 2793


SWiM added this to "complete" the library of benzaldehyde synthesis possibilities. As you see, all routes start with benzene or PhMgBr. The brevitas is typical for Meyer's work. If you want to know more about a particular method, you have to look up the mentioned references.

WOMAN.ZIP: Great Shareware, but be careful of viruses...
07-04-03 21:50
No 444540
      Solventless oxidation with KMnO4/montmorillonite
(Rated as: excellent)

Selective oxidation of alkylarenes in dry media with potassium permanganate supported on montmorillonite K10

Tetrahedron Letters 43 (2002) 51655167

Abstract: The solvent-free oxidation of alkylarenes with KMnO4 supported on montmorillonite K10 is reported. The beneficial effects of microwave and ultrasound irradiation on the reactions is described.


2. Experimental

Oxidation of indan under classical condition
Potassium permanganate (3.16 g, 20 mmol) and montmorillonite K10 (6 g) were ground together in a mortar until a fine homogeneous powder was obtained. Indan  (0.24 g, 2 mmol) was added to this KMnO4/K10 mixture (4.5 g, 9.9 mmol) in a 25 mL round bottomed flask and mixed magnetically at room temperature until TLC (eluent: hexaneethyl acetate) analysis indicated a completed reaction (20 h). The residue was then washed with CH2Cl2 (220 mL). After filtration and removal of the solvent, the crude product was chromatographed on silica gel (eluent: hexaneethyl acetate) to give purified product (0.22 g, 1.7 mmol, 85%) which was identified by comparison with authentic 1-indanone using TLC, melting point (3941C; lit. 42C)

Oxidation of isochroman in the presence of ultrasound irradiation
Isochroman (0.27 g, 2 mmol) and KMnO4/K10 (4.5 g, 9.9 mmol) were finely mixed together and the reaction mixture irradiated in a 25 mL beaker. The progress of the reaction was monitored by TLC. When complete (150 min), the reaction mixture was washed with CH2Cl2 (2 x 20 mL). After filtration and solvent removal the crude product was chromatographed on silica gel (eluent: hexaneethyl acetate) to give purified product (0.24 g, 1.6 mmol, 80%). Identification was by 1H NMR.

Oxidation of tetralin under microwave irradiation
In a 25 mL Teflon beaker, tetralin (0.26 g, 2 mmol) was added to KMnO4/K10 (4.5 g, 9.9 mmol). After 3 min of mechanical stirring, the mixture was irradiated at medium power for 25 min. At the end of exposure to microwave irradiation, the mixture was cooled to room temperature and eluted with CH2Cl2 (2 x 20 mL). After filtration and solvent removal the crude product was chromatographed on silica gel (eluent: hexaneethyl acetate) to give purified product (0.24 g, 1.7 mmol, 82%). Identification was by 1H NMR.

Table 1. The oxidation of alkylarenes by potassium permanganate adsorbed on montmorillonite K10 under solvent free conditions. Effect of microwave and ultrasonic on yield and times requireda
Entry Alkylarene Product Yield timeb Yield timec Yield time d
1 Diphenylmethane Benzophenone 86% 20 h 81% 2.5 h 78% 20 min
2 Ethylbenzene Acetophenone 64% 19 h 52% 3.5 h 44% 12 min
3 Propylbenzene Propiophenone 57% 20 h 54% 2.5 h 50% 20 min
4 Butylbenzene 1-Phenyl-1-Butanone 60% 20 h 61% 3 h 63% 25 min
5 Toluene Benzaldehyde 60% 18 h 52% 1.7 h 54% 12 min
6 p-Xylene p-Methylbenzaldehyde 67% 20 h 53% 2.7 h 65% 35 min
7 o-Xylene No reaction      
8 p-Bromotoluene p-Bromobenzaldehyde 20% 20 h 12% 2 h 15% 30 min
9 Tetralin gamma-Tetralone 87% 20 h 82% 2.5 h 82% 25 min
10 Indan 1-Indanone 85% 20 h 83% 2.5 h 78% 30 min
11 Xanthene Xanthone 81% 22 h 86% 2 h 86% 10 min
12 Fluorene 9-Fluorenone 89% 24 h 87% 2 h 86% 10 min
13 Isochroman Isochroman-1-one 81% 20 h 80% 2h 80% 10 min
14 Phtalane Phthalone 90% 20 h 86% 2h 87% 15 min
15 2,3-Dihydrobenzofurane No reaction      

a Isolated yields. Product identification is carried out by comparison of physical properties (melting points, mass spectra, infrared and NMR spectra) with literature values.
b Temperature = 23C
c Reaction subjected to ultrasonic irridiation
d Reaction promoted by microwave irridation

The candle that burns twice as bright burns half as long
07-05-03 20:05
No 444721
      montmorillonite - product workup?     

LEGO, did the authors mention details on the workup? I remember to have read otherwise a description of the workup of a montmorillonite K10 reaction (solventfree) and it sounded to me quite painful. The catstray properties "sucking up and keep enclosed" of the clay - which are probably responsible for the selectivity of the reaction - seemed to have some drawbacks.

If there is a easy way to wash the product out of the montmorillonite - without very high vacuum or similar - thus would perhaps make this way intersting. Still the ratio of reactands (tetralin to KMnO4/K10 is 1 to 17.... w/w) lets doubt the up-scalability.

But please dont stop posting those findings , also if they lack good yields or look otherwise inconveniant! They are worth gold for showing up principles and giving inspiration where to look, where to search for what.


Honi soit qui mal y pense
(Hive Bee)
09-04-03 07:06
No 457116
      Pressure reactions     

Anyone seen this patent? Yields are kinda lame - but it's quick and dirty. Os' is better - but if you have problems with n2...

process for the production of benzaldehyde by catalytic liquid phase air oxidation of toluene, preferably with 40-50% selectivity.
Patent US6495726
09-05-03 20:52
No 457354
      Crossposting, Hah!     

(Hive Bee)
09-04-03 06:39
No 457114 
Post 457114 (not existing)

         synthesis of benzaldehyde

Water Science and Technology Vol 34 No 10 pp 113120 IWA Publishing 1996
A study on wastewater minimization in indirect electrochemical synthesis of benzaldehyde
Ding Zhou, Zhirong Sun and Wanli Hu

Department of Applied Chemistry, Harbin Institute of Technology Harbin, 15001 China

Development of methods of pollution prevention is a strategic orientation for environmental protection. This paper describes studies on waste minimization in benzaldehyde production by using indirect electrochemical oxidation of toluene instead of the seriously polluting traditional chemical process. The new technology developed eliminates the discharge of wastewater by recycling the reactive solution and gives a higher yield of benzaldehyde


Journal of Applied Electrochemistry  33 (3/4)   p.273-277  March 4, 2003    Kluwer

A new approach to electrochemical production of benzaldehyde from toluene in an undivided cell in the presence of the couple V5+/V4+
Qingfeng Y.1  Xiaoping L.2    and  Xiuling Z.2


Oxidation of toluene to benzaldehyde in the presence of the redox couple V5+/V4+ was carried out in an undivided cell where oxygen gas was continuously bubbled over the cathodic surface and the electrolyte was a mixture of aqueous H2SO4 solution containing V5+ and toluene. Some experimental conditions affecting the current efficiency for benzaldehyde production, such as H2SO4 concentration, current density, V5+ concentration and surfactants, were determined. The maximum current efficiency for benzaldehyde production at ambient temperature was 156.3% under the conditions of 11 M H2SO4, 2.7 10−4 M CTAB, current density 1.25 mA cm−2 and 0.0128 M V5+.
Kudos to Tdurden969 . LT/

(Hive Bee)
09-07-03 22:57
No 457636
      >current density 1.25 mA cm−2 LabTop,     

>current density 1.25 mA cm−2

LabTop, shouldn't cubic centimetres describe current density and not ^2?

Why is the reaction not producing better yields?
Is there any obvious improvements that could bee made by changing the conditions or adding more catalyst?

Don't expect a reply, heh it's too scary in these forums for now, I'm just interested. wink
(Hive Addict)
09-07-03 23:31
No 457639

> LabTop, shouldn't cubic centimetres describe current density and not ^2?

what are you talking about?
current is measured in A (or in this case in mA).
a density is amount per volume or surface. in this case it's current
per electrode surface. the electrode surface is measured in cm^2.
mA per cm^2 = ma / (cm^2) =^-2.

> Why is the reaction not producing better yields?

i have no idea which reaction you are talking about, but over oxidation
might be a good guess.

n'importe quoi
(Hive Bee)
09-08-03 18:10
No 457728
      hypo I just didn't know that.     

hypo I just didn't know that. I'm sure he knew I was just looking for clarification.
I was talking about the current density of the solvent and electrolite.

I was talking about the electrolysis, do you know how to improve the over-oxidation problem?
A reduction in the amount of H2SO4 maybee?
09-09-03 20:04
No 457935
      reaction to benzaldehyd by manganeseperasulfat     

The thread shows a way to make benzald. from toluen by oxidation with Mn02. And some of you said that it wont work well, because the Mno2 has to be "activaded". Here is a easy way to make it from Mn(v)sulfat. A way I used many time!
First get some Mno2. In Germany you can by it as "Manganese-Black" an Wallpaint-color-powder. Thats about 70% Mno2. Then put it in an equimolar amount of H2SO4 (100%) and heat it up. Make it realy hot. (>200C). Let it be there for about half an hour. When I do this, I let The acid become so hot, that white steam comes out. After that, let it cool down. You just have maid Mn(V)SO4. It is soluble in 37% H2SO4 with a deep, chocolate like broun color.
After that put it 1:1 with the toluene in about 60% H2SO4(enough H2SO4, so that nearly everthing disolves). Heat (or cool) it to about 50-60C and stear it well. After 3-4 hours youl will have mostly Benzaldehyd ( in my cases about 70%)
Destill the Benzaldehyd/Toluene out by a simple steam destilation. (Just cook some water out, until there is no oily layer any more)
Wenn you start cooking that stuff, the color of the liquid become sand-like. Thats why the rest of the Mn(V)SO4 breaks down to Mn(II)SO4.
And now the best: just put the liquid in a eloctro. cell(in the anode-part) and put some electricity through it, while stearing. The color will chance to chocolate broun once again, and you can use it again!!! About 6 times!

Hope I could help you!
As you see my english is PERFEKT! But i thought I had to help you....
(Hive Bee)
09-10-03 02:10
No 458012

Rhodium posted these references (Thanks!):

A new approach to electrochemical production of benzaldehyde from toluene in an undivided cell in the presence of the couple V5+/V4+ - (100+% efficency!)
Qingfeng Y.,  Xiaoping L., Xiuling Z.
Journal of Applied Electrochemistry 33(3/4), 273-277 (2003) (../rhodium/pdf /toluene2ba.vanadium.electro-ox.pdf)

A study on wastewater minimization in indirect electrochemical synthesis of benzaldehyde
Ding Zhoua, Zhirong Suna and Wanli Hu
Water Science and Technology 34(10), 113-120 (1996) (../rhodium/pdf /toluene2ba.manganese.electro-ox.pdf)

I havent read through them just yet (just glanced - dinner), figured I'd let ya'all who don't check the Ref thread know.

(Hive Bee)
09-14-03 16:12
No 459026
      Just another oxidiser - Manganese-(III)-sulfate
(Rated as: excellent)

Process for the preparation of an oxidiser:

The process implies the dissolution of manganese-IV-dioxide in sulfuric acid of 50-60% strength in the presence of manganese-II-sulfate. To obtain the oxidiser as a solid, a cold saturated solution of manganese-II-sulfate in water is prepared and concentrated sulfuric acid is added (with cooling, of course) until the solution contains 50-60% sulfuric acid.
The purpose of precipitating the manganese-(II)-sulfate by addition of sulfuric acid is to get the sulfate in finely divided particles, but finely ground manganese-(II)-sulfate could also be used with the same results.
To the crystalline sludge such obtained an equimolar part of manganese dioxide is added under strirring, i.e. for 1 Mol MnSO4 1Mol MnO2 is added. The slush is stirred until the manganese dioxide has dissolved under warming (the reaction is exothermic).
On cooling or upon addition of more (cold) concentrated sulfuric acid the oxidiser settles out in the form of lustrous, brown-red needles.
The product such obtained can be dissolved in organic acids, like acetic acid, and can be used in such solution to react with dissolved organic compounds which otherwise would be destroyed by concentrated sulfuric acid.
The oxidiser itself remains unchanged in its solid form if all traces of water are excluded.

[Translated from:  D.R.P. 205200, titled "Verfahren zur Herstellung eines Oxidationsmittels"]

Italics mine

The reaction involved in this process is:
MnO2 +MnSO4 +2H2SO4 --> Mn2(SO4)3 +2H2O

The preparation of this compound is comparable to the prep. of Mn-(IV)-sulfate, as described by neograviton, but the need of working with fuming hot sulfuric acid is omitted, which seems to be a little
Also, like in neograviton's preparation, there is no need for purchasing watched items like potassium permanganate for the preparation of activated manganese dioxide wink

An educated guess at last:
For the preparation of benzaldehyde from toluene, I think the procedure described by neograviton should work equally well with the use of abovementioned Mn-(III)-sulfate, there is even no need of isolating this compound from the 60% sulfuric acid solution, use it as it is.

Quidquid agis, prudenter agas et respice finem!
(Hive Bee)
10-30-03 23:50
No 467877
      You can activate MnO2 by impregnating it with HNO3     

Or by heating at 110-125 degrees for 24-52 hours in a stove.
Both might work.
Have read some papers on that.
Seems MnO2 is a real touchy one...
Ning thinks that drying the stuff is kind of a waste if you are plunking back into water, as ning is. The nitric acid bit might not be so hard to do, though.
More details when time avails.
(Synaptic Self-Mutilator)
10-31-03 01:42
No 467898
      An easier way?     

Has anyone ever tried Fe(II) (perhaps with Cu(II)?) and H2O2 (perhaps with H+) on toluene? This would be a completely OTC approach that would be very practical... of course getting to benzaldehyde is only part of the struggle.

Catalytic H2O2 with copper, iron, manganese or a bunch of other transition metal compounds is well known chemistry so perhaps the info is already out there... this would be a fundamentally awesome synthesis.
(Hive Bee)
11-01-03 11:28
No 468094
      I've thought about the possibility of ...
(Rated as: good read)

I've thought about the possibility of replacing peroxodisulfate with H2O2 too. It turns out that the reaction is based on the reduction of peroxodisulfate ion by a metal ion to sulfate radical and a sulfate ion. The sulfate radical is the species that abstracts an electron from toluene forming toluene radical cation thusly starting the oxidation. Analogically hydrogen peroxide is reduced into hydroxyl radical and a hydroxyl ion, but the hydroxyl radical is electrophilic and reacts with toluene forming a hydroxycyclohexadienyl radical which most likely results in the formation of a phenols, so getting good yields of benzaldehyde from toluene isn't likely to happen.frown

By the way, in the patent (Patent US4146582) they say that acetic acid, for one, is a "particularly suitable organic solvent" for the reaction, but according to literature the yields are going to be lower due to formation of benzyl acetates. Typical of patents. They also say nothing about the ratio of methanol and water used in the persulfate solution... maybe the point is to use the same ratio as in the reaction mix.

J. Chem. Soc. Abstracts 1963, 2897-2905
J. Am. Chem. Soc. 97(2), 363-365 (1975)
J. Org. Chem. 48(25), 4910-4914 (1983)
Synthesis 1980, 477-479
J. Am. Chem. Soc. 106(24), 7573-7578 (1984)
Tet. Lett. 22(27), 2605-2608 (1981)

fear fear hate hate
(Hive Addict)
11-17-03 15:03
No 471369

Patent US6495726

Chromic this patent uses air, toluene and cheap metal catalyst such as salts of Fe and Mn or Cu.

tdurden posted the same one i see, but it's relevent to your thoughts in case you forgot to read it.

The present invention relates to an improved process for the production of benzaldehyde with 40-50% selectivity comprising by catalytic liquid phase air oxidation of toluene. The process involves providing a continuous flow of air in the presence of a catalyst such as salts of Fe, Co, Mo and Ni, and preferably a co-catalyst such as salts of manganese or copper, a promoter which may also be a bromine source, and a carboxylic acid solvent selected from the group consisting of acetic, propionic, benzoic acids ranging between 0.05 to 0.3 wt. times with respect to toluene, at a temperature ranging between C. and pressures in the range of 1-10 bars for a period of 0.5-1.5 hours to obtain benzaldehyde (40-50%) along with other by-products.

You don't need 2 Bee High to follow the goings-on @The-Hive--Just Addikted!
(Chief Bee)
11-25-03 15:16
No 473076
      Benzoic Acids to Benzaldehydes     

Here is a moderately interesting preparation of a benzaldehyde from its corresponding benzoic acid, taken from  J. Org. Chem. 435-439 (1964). What I find hilarious with this synthetic sequence is the absurdly excessive amounts of solvents and reagents used - In the workup of 3,5-Dimethoxybenzyl Alcohol, a little over 20g of product is taken up in three liters of diethyl ether, and then washed with with two liters of water, and one liter each of  aqueous NaOH and brine! Then, to produce 12g of the corresponding benzaldehyde, five liters of hot chloroform is used in the reaction and workup... If someone was caught wasting so much chemicals these days, they would be fired on the spot

3,5-Dimethoxybenzyl Alcohol

3,5-Dimethoxybenzoic acid (25.0g, Rf 0.04) was dissolved in warm, dry tetrahydrofuran (400 mL), and this warm solution was added continuously over 90 min to a gently refluxing suspension of lithium aluminum hydride (10 g) in tetrahydrofuran (100 mL). When the addition was complete the mixture was boiled under gentle reflux for 4h, then cooled (ice-water bath). The excess hydride and the complex were decomposed by cautious addition of ethyl acetate (60 mL), water (60 mL), and 2N aqueous hydrochloric acid (100 mL) . The volume of the resulting suspension was reduced to 150 mL (rotatory evaporator, bath temperature of 40C), diluted by addition of water (200 mL), and extracted with 6x500mL ether. The ether extract was washed with water (1 L), 2N aqueous sodium hydroxide (1 L), water (1 L), and brine (1 L), then dried over sodium sulfate. The solvent was eliminated from this dried extract, leaving a colorless solid (22.9g), which was crystallized from hexane, giving 3,5-dimethoxybenzyl alcohol as needles (21.8g, 94%), mp 46.5-47C (lit.[7] mp 47-48C); TLC Rf 0.14.[6]


Freshly prepared "active" manganese dioxide [8] (201g) was added to a solution of 3,5-dimethoxybenzyl alcohol (17.8g) in dry, ethanol-free chloroform (2 L), and the mixture was stirred in an atmosphere of nitrogen for 24 h at room temperature. The mixture was filtered, and the residue was washed with 6x500mL portions of boiling chloroform. The solvent was eliminated from the combined filtrate and washings, leaving a colorless crystalline solid (13.9g), mp 43-45C. This was crystallized from pentane, giving 3,5-dimethoxybenzaldehyde as prisms (12.8g, 72%), mp 45-45.5C (lit.[9] mp 48C); TLC Rf 0.57.[6]

References & Notes

[6] Thin layer chromatography (TLC) was conducted using silica as the absorbant. 95:5 CHCl3/EtOAc as the developing solvent. and iodine as the visualizing agent; Rf values reported are only reproducible to 0.05.
[7] J. Am. Chem. Soc. 70, 664 (1948)
[8] J. Chem. Soc., 1094 (1952)
[9] J. Am. Chem. Soc. 76, 133 (1954)
(Horrible Personality)
11-25-03 15:45
No 473081
      the best way to benzaldehyde     

from toluene is in reality:
- oxidise the toluene to benzoic acid with KMnO4 or else
- or be bright and get some benzoic acid directly
- dehydrogenate the benzoic acid at 500C in a furnace tube with ZnO as catalyst to benzaldehyde with 95percent selectivity in excellent yields (single pass).

This is a standard process in industry, but easily and safely adaptable for clandestine use. The advantage is the dehydrogenation being strongly endothermic and this way being inherently safe and the dehydrogenation is going to stop at the benzaldehyde as long the temperature doesnt exceed 550C. Works for many substituted benz-dehydes also.

There are no further reagents or carrier gas needed. Some propane or better electricity for heating and done. Catalyst is good for some hundred hours before regeneration is needed - no problem.

"divine is the way of the tube" - Randolph Carter
(Chief Bee)
11-25-03 21:58
No 473147
      Toluene to Benzaldehyde using Co(II)-Peroxygen
(Rated as: good read)

Oxidation of Substituted Toluenes to Benzaldehydes using Solid Peroxygen Sources Catalysed in the Presence of Bromide and Cobalt(II)Acetate
Craig W. Jones, Anthony Hackett, Ian Pattinson, Alexander Johnstone, Sharon L. Wilson
J. Chem. Research (Synopsis), 438-439 (1996) (../rhodium/pdf /toluene2ba.cobalt-peroxygen.pdf)
J. Chem. Research (Miniprint), 2501-2525 (1996) Full Article

Substituted toluenes can be selectively oxidized to the aldehydes employing solid peroxygens in the presence of cobalt(II)acetate, acetic acid and an inorganic bromide source.
(Hive Bee)
12-20-03 18:37
No 478010
      A question     

- dehydrogenate the benzoic acid at 500C in a furnace tube with ZnO as catalyst to benzaldehyde with 95percent selectivity in excellent yields (single pass).
There are no further reagents or carrier gas needed. Some propane or better electricity for heating and done.

This part confuses me, is there a mistake perhaps? In theory benzoic acid could be hydrogenated to benzaldehyde or benzyl alcohol could be dehydrogenated to benzaldehyde; but hydrogenation would require hydrogen gas and the catalyst sounds rather like a dehydrogenation than a hydrogenation catalyst. I'd appreciate a reference, the method sounds interesting you see.

fear fear hate hate
(Hive Bee)
12-21-03 20:18
No 478220
      Me too, please. ;-)     

Also could you give whatever is on your mind regarding the basic apparatus setup Org?

Is something similar to an acetaldehyde apparatus? Does the ZnO have to be specially prepared?

Rh, in your reference, do you think that Oxone would bee a good solid peroxygen?

Also, do you think it would work for non-substituted toluene? (I guess that's why you posted it here but i better ask.)

'cobalt(II)acetate, acetic acid and an inorganic bromide source.'

Would these have to be omitted or left out in the case of non-substituted toluene?
(Chief Bee)
12-21-03 22:44
No 478250
      Rh, in your reference, do you think that Oxone     

Rh, in your reference, do you think that Oxone would bee a good solid peroxygen?

Also, do you think it would work for non-substituted toluene? (I guess that's why you posted it here but i better ask.)

'cobalt(II)acetate, acetic acid and an inorganic bromide source.'

Would these have to be omitted or left out in the case of non-substituted toluene?

1) Probably, but only if you cannot get any of the already tested oxidants - it will save you some ratio experimentation.

2) Yes.

3) No, it'll be the same.

The Hive - Clandestine Chemists Without Borders
(Horrible Personality)
12-25-03 20:10
No 479018

moo, you are absolutely right, I confused some procedures, my bad....

Here is it right:
C6H5COOH + H2 = C6H5CHO + H2O
Hydrogen IS needed as reactand and carrier gas.

Appl. Catal. A. 220 (2001) 41-49

Catalyst preparation:
(As ZnO is the most active and selective catalyst here, which also works at lower temperatures I describe only the preparation of this)

Zinc basic carbonate - ZnCO3.2ZnO.3H2O - is heated under nitrogen (any inert gas will do the job I suppose) at a rate of 10°C/min up to 250°C and held at this temperature for 4hours. Then the temperature is rised (10°C/min) up to 400°C for 6min. then let cool down.

Reactor tube: Glass, 10-15mm length, 5mm diameter, filled with 0,5gram catalyst.
(Scale up by using the same catalyst/volume and length/width ratio)

Temperatur of the reactor:
325°C = 80% conversion by 100% selectivity - no byproducts.
360°C = 100% conversion with 95%+ selectivity - some toluene is formed.
Over 360°C the rate of produced toluene rises rapidly and some other byproducts form.

Oh, yes we talk here of deoxygenation of benzoic acid to benzaldehyde. wink
The water formed cools and makes temperatures controlable.

Bubble dry hydrogen through hot benzoic acid and attach a nozzle before the mix enters the hot tube - for security. (this is a MUST HAVE for all tube furnances! Its so easy to stay save)

Addon: If nitrogen is used as carrier gas and the hot tube flushed with nitrogen before use, at temperatures exceeding 400°C benzene is formed in good yields.

thanks moo for asking - now its fixed. smile

12-30-03 03:20
No 479722
      Reference Uploaded
(Rated as: good read)

Applied Catalysis A: General 220 (2001) 4149

Deoxygenation of benzoic acid on metal oxides
1. The selective pathway to benzaldehyde
M.W. de Lange, J.G. van Ommen, L. Lefferts


Chemistry is our Covalent Bond
(Hive Bee)
12-30-03 20:19
No 479815

When you said Act. Mno4 needed to be used, for good yields, what do you consider good yields?  Once toulene is oxidize to benzaldeyde, what are the chances that the aldehyde will be oxid. futher after the temp rises.  To this day, I do not under Mn compounds, most of there mechanism or not completly understood. ADDkid 
Also, if the aldehyde is futher oxy. do you have to keep the temp cool for seprat.
(Chief Bee)
12-30-03 23:10
No 479835
      Benzaldehydes with activated MnO2     

Good yields are 75-90% according to the procedure in Post 354314 (Rhodium: "General Method for the Preparation of ...", Chemistry Discourse) (This thread!)

Preparation of activated MnO2 (Not MnO4!):

Post 352497 (Mountain_Girl: "Activated MnO2", Chemistry Discourse)
Post 352508 (blondie: "activated MnO2", Chemistry Discourse)

The Hive - Clandestine Chemists Without Borders
(Chief Bee)
12-31-03 04:09
No 479888
      More on Toluene -> Benzaldehyde
(Rated as: good read)

In addition to the above, please check out the following references, all of which should be pertinent to the MnO2/H2SO4 oxidation of toluene to benzaldehyde:

Reactant: Toluene
Reagents: Sulfuric Acid (H2SO4), Manganese dioxide (MnO2)
Product: Benzaldehyde
Patent DE175295
Patent DE101221
Patent DE107722
J. Chem. Soc. 91, 263 (1907)
Zh. Obshch. Khim. 4, 936-940 (1934)
Chem. Zentralbl. 106, II, 3750 (1935)
Chem. Zentralbl. 76, I, 359 (1905)

Post 244957 (Chemikaze: "Benzaldehyde via MnO2 oxidation of toluene", Novel Discourse)
Post 463350 (Antoncho: "A great piperonal patent", Novel Discourse)
Post 208782 (PolytheneSam: "Re: The easiest synth of benzaldehyde from toluene", Chemistry Discourse)
Post 429514 (Assholium: " - ?", Russian HyperLab)
Post 224776 (fructose: "P2P - 100% OTC !?!", Chemistry Discourse)

The Hive - Clandestine Chemists Without Borders
(Hive Bee)
03-08-04 18:18
No 493769

Post 437235 (Organikum: "B-dehyde", Stimulants)

Honi soit qui mal y pense
(Hive Bee)
03-09-04 02:57
No 493837
      Benzoic acid to benzaldehyde or benzene
(Rated as: good read)

I like the ref very much, thank you Organikum and Lugh. Those tube furnaces don't look that scary after all.wink Here is the second part of the article series:

Deoxygenation of benzoic acid on metal oxides. 2. Formation of byproducts.
de Lange, M. W.; van Ommen, J. G.; Lefferts, L.
Applied Catalysis, A: General, 231(1-2), 17-26 (2002).  Journal written in English.
CAN 137:142127  ISSN 0926-860X

Benzene, benzophenone, toluene and benzyl alc. are byproducts in selective redn. of benzoic acid to benzaldehyde on ZnO and ZrO2 catalyst.  The pathways to the byproducts are discussed and a complete overview of the reaction network is presented.  Benzene and benzophenone are products of the decompn. of the strongly adsorbed benzoic acid at elevated temps.  Toluene is formed by deoxygenation of benzaldehyde at O vacancy sites.  Direct hydrogenation of benzaldehyde yields benzyl alc.  Selectivity to byproducts is not only detd. by the reaction temp., but also by the degree of surface redn. and the difference in adsorption strength between reactant and product.  At <360 Deg, benzoic acid forms a benzoate layer which is stable and prevents readsorption of benzaldehyde.  Redn. of the catalyst by H leads to a small no. of O vacancy sites which deoxygenate benzoic acid to benzaldehyde, and as a result, selectivity to benzaldehyde is very high (>95%).  Higher temps. induce decompn. of the benzoate layer to benzene, and more importantly, enhance the degree of redn. of the catalyst, which results in the formation of toluene from benzaldehyde.

fear fear hate hate
(Wonderful Personality)
03-09-04 15:11
No 493948
      Benzoic acid to benzaldehyde by electrolysis     

The not so new laugh Patent DE123554 from 1899 describes the electrolytic conversion of benzoic acid to benzaldehyde by an interesting way.

It describes that 45 to 50 parts finely powdered benzoic acid are intimately mixed with 55 to 50 parts of graphite, pressed under heat (100C, 30atm) and this is used as cathode in an electrolytic cell. The cathode is placed in an glascylinder which is surrounded by an cylindrical lead anode (or platinum). Electrolyte is 20% H2SO4 saturated with benzoic acid at 20C. Water is permanently refilled near the anode at the bottom of the cell by an tube, voltage is 12V to 15V and current density is 1,5Amp per dm2 of cathode surface. Benzaldehyde separates on the surface and is removed from time to time whilst water is refilled, the cathode decomposes by time and the graphite precipitates at the bottom of the cell.

Dont say thats far out. It is much easier as it looks as compressing the benzoic/graphite in a steeltube cannot be so hard - a threaded rod or a jack will work fine I suppose. No diaphragm needed, nor exotic electrolyte.......

The patent says the method works for oxidation as reduction the same.
Examples named but not given are:

- carboxylic acids overall
- paraformaldehyde
- aromatic nitrogenous compounds
- alkaloids
- .....

- anthracene
- cellulose

Shareholder of Paranoid Fucks inc.
(Hive Bee)
03-09-04 23:29
No 494043
      PhCHO from toluene, air and metal catalyst     

The best one I ever saw and only one tried of all the many ways to oxidize toluene to benzaldehyde is found in The Journal of Chemical Education from around 1953 if my memory is correct. If someone who has acess to this journal could find this it would surely interest a lot of people.

Air is carrier gas and O2 source which is bubbled through boiling toluene (use bubble counter for determining flow rate) and passed through a vertical stainless steel tube packed with catalyst at 350C and then into a condenser. Very little side products if temperature is kept stable. The article has drawings for a tube heated in a molten lead bath but it is much easier to wrap the tube with NiCr wire (toaster or blow dryer) about 300 watts controlled with a triac type dimmer and monitored with a thermocouple (Type K from a water heater flame sensor).

The article is very good and compares many different metal catalysts (Fe, Zn among the simple ones and some more exotic) with yields and reaction conditions. I made Cerium Molybdate, coated alumina pellets with it and got about 85% molar yield.

The beauty of the tube method is continuos production with very little work. A 1/2 X 24 inch tube gives about 1 liter a day and runs for 2 weeks or so before regeneration of the catalyst is required.

I tried the JACS website to find the article but since I am no longer a member the Journal of Chemical Education is unavailable to to me.
(Hive Bee)
03-14-04 23:53
No 495155
      Two articles on catalytic air oxidation of toluene     

I was unable to find the article from the Journal of Chemical Education that Bio mentions. However, in a private communication he indicated that the information was originally published in Industrial and Engineering Chemistry, and I was able to find a couple of articles on that topic.

Bio said:
"Parks is the author and the second article has the drawing I refered to. I believe the JCE article must have been a compilation of Parks work. I did not see Cerium Molybdate or the higher yields on the list in a quick look just now, so this must be a later article. That's why I picked it as catalyst. It is very easy to make from Cerium Nitrate and Molybdenum ammonium something or other."

I performed a further search, searching for Parks as author and cerium or ceric catalyst as keywords; I turned up an additional article about air oxidation of xylene to toluic aldehyde and phthalic anhydride. There were no articles by that author using a cerium/molybdenum catalyst.

Perhaps I will be able to find the JCE article later, now that I know what name to look for. Here are the articles themselves (Rhodium, please mirror if they're worthy):

19th century digital boy
(Hive Bee)
03-22-04 17:59
No 496655
      benzaldehyde from toluene     

Great find Polverone. It's been so long ago that I forget most of it but since these articles came way before the days of computers the indeces are not always that complete. I may have adapted the Cerium Molybdate from one of the Xylene oxidation articles. These are also very good for understanding the basic parameters required to design a catalyst loaded furnace tube and Parks gives enough data on space time etc. that one may easily design one in the size required by the materials at hand. I wonder if Parks was affiliated with a major company because he reveals more information than is usually found in these types of patentable topics. Many Bees will enjoy the Journal of Industrial and Engineering Chemistry as it contains practicle information related to the initial scale up experiments on most important reactions progressing from the bench to something more useful and often actually simpler than the parent procedures. The many articles on Chloromethylation with formaldehyde etc. come to mind.
(Wonderful Personality)
03-30-04 02:07
No 498021
      H2O2 toluene oxidation (vanadium catalyzed)     

I am refering here to moos post about the (im)possibility to use H2O2 in the oxidation of toluene.

The earliest example was the oxidation of toluene to benzaldehyde. A divided cell was used and the anode was used to oxidize Mn(II) to Mn(III) in sulfuric acid while the graphite cathode was used to reduce oxygen to hydrogen peroxide. The oxidation of toluene was carried out in situ in the catholyte in the presence of V(IV) as a catalyst while the Mn(III) was reacted with toluene external to the cell after the electrolysis


January 1999 Vol. 4 No. 1
Electrogenerated Hydrogen Peroxide -
From History to New Opportunities
by Derek Pletcher

the reference for the above:
- J-J. Jow, A-C. Lee and T-C. Chou, J. Applied Electrochem., 17 (1987) 753

somebody can look this up and post it here?
Thus would be GREAT!

Ok, the persulfate part is wellknown and not new at all, but the hydrogen-peroxide/vanadium(IV/V) part is new I think (but I maybe wrong of course). Anyways this sounds like a possible method to produce benzaldehyde from toluene with excellent selectivity and in good yields by using H2O2 and a catalyst - the electrolytic part may be neglectable for our purposes.


EDIT: I just realized that this correspondends to the article LabTop posted (courtesy TurdenXXX) - as the described method of bubbling oxygen over the cathode will of course produce hydrogen peroxide. Nevertheless, the question to be asked is: Will this work without in-situ generation of H2O2? If yes - and I think it will work - catalyst preparation and conditions optimized for a non-electrolytic reaction?


Bee-Research International Ltd.
(Hive Bee)
08-09-04 10:30
No 524391
      In regards to Organikum's post regarding ...     

In regards to Organikum's post regarding Patent Patent DE123554 about electrolytic conversion of benzoic acid to benzaldehyde, the patent says the method works for oxidation as reduction the same. So cant we do the reverse and oxidise tolune to benzaldehyde at the anode?

If toluene can be aquired and one would originally oxidise this to benzoic acid via KMnO4 to benzoic acid, it seems more practical to electrolytically oxidise to benzaldehyde.
(Wonderful Personality)
08-09-04 20:46
No 524452
      No. This says you can oxidise benzaldehyde to...     

No. This says you can oxidise benzaldehyde to benzoic acid this way.

so near, so far......
(Chief Bee)
09-16-04 03:00
No 531521
      3,4,5-Trimethoxytoluene to 3,4,5-TMBA (92%)
(Rated as: excellent)

The Selective Liquid-Phase Oxidation of 3,4,5-Trimethoxytoluene to 3,4,5-Trimethoxybenzaldehyde
Nobumasa Kitajima, Kazuya Takemura, Yoshihiko Moro-Oka, Tadatsugu Yoshikuni, Mitsuo Akada, Yoshihisa Tomotaki, and Masatoshi Taniguchi
Bull. Chem. Soc. Jpn., 61, 10351037 (1988) (../rhodium/pdf /345-tmba.345-meo-toluene.pdf)

The selective liquid-phase oxidation of 3,4,5-trimethoxytoluene to 3,4,5-trimethoxybenzaldehyde, an important chemical intermediate for medicine production, was developed; when 2.0 mmol of the reactant was heated at 110C for 2 h in an autoclave under 3 atm O2 with 10 ml of acetic acid in the presence of 0.75 mmol of Co(OAc)2-Mn(OAc)2 (3:1 mole ratio), a 92% yield of the aldehyde was obtained.

The Hive - Clandestine Chemists Without Borders