Sciencemadness Discussion Board

Benzene to benzaldehyde conversion

bluamine - 6-7-2022 at 10:14

Hi everyone!
I'm studying this reaction that realizes the equation below:

C6H6 +CO + HCl ----CuCl/anh. AlCl3----> C6H5CHO
Now the question is how much pressure is needed to a achive this conversion, and can it be done in the lab?

[Edited on 6-7-2022 by bluamine]

Metacelsus - 6-7-2022 at 13:14

This is known as the Gattermann–Koch reaction and can be done at atmospheric pressure. See the attached paper.

But be careful, working with CO sounds like a good way to kill yourself. And benzene isn't very nice either.


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bluamine - 8-7-2022 at 03:33

Quote: Originally posted by Metacelsus  
This is known as the Gattermann–Koch reaction and can be done at atmospheric pressure. See the attached paper.

But be careful, working with CO sounds like a good way to kill yourself. And benzene isn't very nice either.

Oh thank you!! I'll check it out
Well yes carbon monoxide is very toxic and benzene is carcinogenic so it must be done outside or in a fumehood, and gloves with mask must be worn.
By the way is there any good way to produce carbon monoxide in the lab other than calcium carbonate/zinc metal reaction?
I had the intention to do this reaction under atmospheric pressure until I've found some claims about doing it under high pressure

[Edited on 8-7-2022 by bluamine]

Keras - 9-7-2022 at 02:31

Quote: Originally posted by bluamine  

By the way is there any good way to produce carbon monoxide in the lab other than calcium carbonate/zinc metal reaction?
[Edited on 8-7-2022 by bluamine]


I wasn’t even aware that gave rise to CO. You can try dehydrating formic acid with concentrated sulphuric acid (or phosphorus pentoxide?):

HCOOH → H₂O + CO. That actually works (with sulphuric acid), as demonstrated by a Chemplayer’s video (that I replicated).

bluamine - 9-7-2022 at 07:05

Quote: Originally posted by Keras  

I wasn’t even aware that gave rise to CO. You can try dehydrating formic acid with concentrated sulphuric acid (or phosphorus pentoxide?):

HCOOH → H₂O + CO. That actually works (with sulphuric acid), as demonstrated by a Chemplayer’s video (that I replicated).

I just don't have any source for formic acid actually but I'm looking forward
It would be interesting though

[Edited on 9-7-2022 by bluamine]

Keras - 9-7-2022 at 08:02

Quote: Originally posted by bluamine  

I just don't have any source for formic acid actually but I'm looking forward
It would be interesting though


Apparently, that works with oxalic acid, too, which is much more OTC (source: Wikipedia page on CO)

Fantasma4500 - 9-7-2022 at 08:47

Zn + CO2 = CO + ZnO
ZnC2O4 = CO + CO2 + ZnO 350-500


CaC2O4*H2O, hydrate gone after 170*C
decomposes into CaCO3 + CO at 475*C
further decomposes at 755*C to CaO + CO2

formates does not surprisingly form CO on decomposition and the products depends on if its zinc, lead, lithium formate etc
infact, - sodium formate may be of use

It was shown that after melting at 253°C, sodium formate slowly decomposes by hydrogen loss to Na2CO3, CO and Na2C2O4 at 330°C.

Bonee - 12-7-2022 at 03:23

Why would you want to work with very carcinogenic benzene? its easy peasy with PTC oxidation of benzyl alcohol with hypochlorite

PellePeloton - 12-7-2022 at 04:59

Quote: Originally posted by Bonee  
Why would you want to work with very carcinogenic benzene? its easy peasy with PTC oxidation of benzyl alcohol with hypochlorite


Many things are relative. Put in perspective, benzene is not THAT carcinogenic.

Proof? There is still about 1% of benzene in unleaded gasoline (plus 4% other aromatics). So every time someone fills the tank, he sloshes around with about 500 ml of benzene. No hood, no mask, no big problem.

In a lab, work in a hood.

Texium - 12-7-2022 at 08:28

Quote: Originally posted by PellePeloton  
Proof? There is still about 1% of benzene in unleaded gasoline (plus 4% other aromatics). So every time someone fills the tank, he sloshes around with about 500 ml of benzene. No hood, no mask, no big problem.
And we all know that it's completely harmless to inhale gasoline fumes /s.

Triflic Acid - 12-7-2022 at 20:30

If it were really that bad it would be banned. I'm not saying it's safe, but it's not the liquid cyanide it's portrayed as. It's like asbestos. Don't be stupid and try to drink it, and you're fine.

Keras - 12-7-2022 at 21:44

I think like most carcinogenic substances, the major risk comes from daily, or repeated exposure at relatively low, non-alarming levels. IIRC, benzene in itself is not carcinogenic. But enzymes in the liver oxidise it, and those oxidised products are liable to attack DNA, denature enzymes and cause other disorders. The same thing happen with paracetamol – the molecule is benign, but one of its metabolites is not. The body attempts to render the product more soluble by oxidising it, which makes it more polar, but in this it also makes it quite deleterious.

What is surprising, though, is that toluene is not suspected of being even remotely carcinogenic, albeit differing from benzene by only a single methyl group.

myr - 13-7-2022 at 03:29

Quote: Originally posted by Keras  
I think like most carcinogenic substances, the major risk comes from daily, or repeated exposure at relatively low, non-alarming levels. IIRC, benzene in itself is not carcinogenic. But enzymes in the liver oxidise it, and those oxidised products are liable to attack DNA, denature enzymes and cause other disorders. The same thing happen with paracetamol – the molecule is benign, but one of its metabolites is not. The body attempts to render the product more soluble by oxidising it, which makes it more polar, but in this it also makes it quite deleterious.

What is surprising, though, is that toluene is not suspected of being even remotely carcinogenic, albeit differing from benzene by only a single methyl group.


My understanding is that it is oxidized directly to benzoic acid, which is then eliminated: the methyl is preferentially attacked, so none of the reactive aromatic oxidation products are formed

Keras - 13-7-2022 at 10:51

Quote: Originally posted by myr  

My understanding is that it is oxidized directly to benzoic acid, which is then eliminated: the methyl is preferentially attacked, so none of the reactive aromatic oxidation products are formed


Makes sense. Also, benzoic acid (and other molecules of the same ilk) is metabolised to hippuric acid by reaction with glycine.

bluamine - 14-7-2022 at 07:20

Quote: Originally posted by Keras  
What is surprising, though, is that toluene is not suspected of being even remotely carcinogenic, albeit differing from benzene by only a single methyl group.

What's more surprising is that its derivative TNT is suspected to be carcenogenic

draculic acid69 - 14-7-2022 at 18:40

Quote: Originally posted by bluamine  
Quote: Originally posted by Keras  
What is surprising, though, is that toluene is not suspected of being even remotely carcinogenic, albeit differing from benzene by only a single methyl group.

What's more surprising is that its derivative TNT is suspected to be carcenogenic


Yeah carcinogenic isn't the main problem with tnt.
In fact I'd say it's a minor concern.

Keras - 14-7-2022 at 23:23

Quote: Originally posted by bluamine  

What's more surprising is that its derivative TNT is suspected to be carcenogenic


I would argue not. –NO₂ containing molecules are now suspected to be carcinogenic, proof being the recent classification of nitrites salts as such by the EU.

That being said, yeah, I’m not expected to drink or eat TNT anytime soon, so that’s a minor issue to me. :p

unionised - 15-7-2022 at 01:02

I'd have thought the easy way to get CO was from CO2 and C; pass the gas over hot charcoal.

It's Friday. Like many other people I will be drinking alcohol this evening, even though it's a known carcinogen.


teodor - 15-7-2022 at 01:13

Depression leads to cancer. Do all experiments in a good mood and don't lose interest in chemistry and Nature. CO is far more dangerous than benzene. Buy CO detector and place it somewhere in your room, it can alarm you with a loud sound in case of danger. If you like accurate work do everything in a fume hood a turn it on if you can smell C6H6. If you cannot you are perfectly right with safety.

zed - 15-7-2022 at 02:36

Lots of better ways to make Benzaldehyde. Oxidation of Benzyl Alcohol or Chlorination of Toluene, are both superior to utilizing CO and HCl. Though to be fair, Chlorination of Toluene, followed by hydrolysis... produces some very unpleasant intermediates.

Fantasma4500 - 18-7-2022 at 03:48

i was looking into reactions of ethylbenzene and xylene, xylene can be oxidized into toluic acid which can then be reduced to toluene
toluene may then be oxidized partly into benzaldehyde
there was something about ethylbenzene, acetophenone? i lost track of it but that was also useful
many paint removers contain a mix of xylenes and ethylbenzene so its decently OTC

as for oxidation agents im not sure how to go about it, you might be looking at hot H2CrO4 with the solvent dropped into it carefully, mixing up maybe 3:1 chromic acid and solvent and then heating can make it blow up, very annoying mess.
Na2S2O8 - persulfate maybe, manganate?

lead dioxide can form ozone without falling apart, this could be utilized with a perchlorate solution

bluamine - 21-7-2022 at 17:06

Quote: Originally posted by Keras  

That being said, yeah, I’m not expected to drink or eat TNT anytime soon, so that’s a minor issue to me. :p

I'm wondering if it has a similar odor/taste of something common so you may have it in your food but have any ide :)

[Edited on 22-7-2022 by bluamine]

bluamine - 21-7-2022 at 17:08

Quote: Originally posted by zed  
Lots of better ways to make Benzaldehyde. Oxidation of Benzyl Alcohol or Chlorination of Toluene, are both superior to utilizing CO and HCl. Though to be fair, Chlorination of Toluene, followed by hydrolysis... produces some very unpleasant intermediates.

I guess that reaction is like chlorination of methane, give a lot of byproducts...