Decarboxylation

[YT2095]

does anyone know of a simple effective method for this to be done to Benzoic Acid, to make Phenol?

 

I`ve googled till my fingers are sore, and can`t find a usable method, and yet 90% of Phenol is produced this way (damn their trade secrets!).

maybe I`m missing something?

the best I can come up with so far is: http://www.chemguide.co.uk/organicprops/acids/decarbox.html

 

giving me Benzene.

[jdurg]

Couldn't you esterify the benzoic acid and then reduce it with LiAlH4?

[YT2095]

I could make an ester sure, maybe a methyl or ethyl benzoate, I just don`t have any lithium alu hydride

 

I tried the link above (using straight NaOH prills), I did get my benzene gas without a problem, although I think I overdid it on the hydroxide a little, so I Know that part works, I need to rip the COOH from the R and idealy leave just the OH.

[jdurg]

What about sodium borohydride? That would work as well, albeit a bit slower than with lithium aluminum hydride.

[YT2095]

I have no Hydrides at all here.

[jdurg]

Then i'm afraid that the reaction of turning benzoic acid to phenol simply cannot happen. In order to remove the COOH group you need a good reducing agent. The only other methods of reduction won't cleave the entire COOH group off of there. Instead you'll get a toluene with an OH group on the -CH3 appendage.

[YT2095]

there has to be Another path though! I`m sure of it.

if you can get phenol from aspirin and sulphuric acid, there`s got to be a way to either replace the COOH with something else that can be replaced again easily.

ok stripping down to Benzene works but it`s a little extreme

but it does demonstrate that there are many OTHER pathways and routes that can be taken, surely?

[jdurg]

Wait a minute. I just thought of another method. First off, do you have any hydroxylamine? (H2N-OH). If you do, then you can esterify your benzoic acid with some benzene that you say you have produced. At this point, add some hydroxylamine to your benzyl-benzoate ester. If this is done in the presence of sodium hydroxide, you'll wind up with phenol and the benzene derivative of hydroxamic acid.

[YT2095]

aint that just a pi$$er, I don`t have any of that either, ammonium hydroxide is as good as it gets, well that and Other Ammonium salts (nitrate, perchlorate, chloride).

[jdurg]

Okay, I just thought of another method. How about the hydrolysis of chlorobenzene? First off, take your benzoic acid and convert it all to benzene. Then take your benzene and subject it to chlorine gas and Iron (III) Chloride. This will give you mono-chlorobenzene. Take this chlorobenzene and reflux at about 350 degrees Celcius with sodium hydroxide and water. This will result in sodium phenoxide. Add some acd to this (probably HCl would work) and you'll get phenol and sodium chloride!

[YT2095]

Hmmm... how do you reflux at 350c with Water in it, without Breaking something?

[jdurg]

Not too sure about that. (Organic was never a major strong point). I'm sure that just heating strongly with NaOH and some water would work just fine. The gist of it is, you need to heat the chlorobenzene with NaOH in order to replace the -Cl with an -O:Na+ group. Then neutralize that with acid to get the phenol. Perhaps 'reflux' wasn't the word I was looking for.

[YT2095]

Not too sure about that. (Organic was never a major strong point). I'm sure that just heating strongly with NaOH and some water would work just fine. The gist of it is, you need to heat the chlorobenzene with NaOH in order to replace the -Cl with an -O:Na+ group. Then neutralize that with acid to get the phenol. Perhaps 'reflux' wasn't the word I was looking for.

 

I`m with ya

and Orgo is kinda new to me also, that`s why I`m doing this stuff, hopefully I`ll learn a bit as I go along

 

IIRC, it`s all about replacements of the funtional group, the actualy benzene itself it quite secure in most synths and so can be more or less ignored. That in a way makes things a little more simple (my way of looking at it).

now I only have a limited supply of this Sodium benzoate (and subsequent benzoic acid), so all experiments will be done at test tube level until I find a good product and method of production, to make it en mass and then use THAT as the precursor (base/starting point) for other orgo experiments, I figured Phenol was a good place to start as it`s quite simple and basic, and stores well as opposed to Benzene liquid when you have a small child in the same building.

[YT2095]

ok I`ve had another thought, what if I go Back a step, to the point before benzoic acid, when it was sodium benzoate. could something be workable from That point onwards?

[jdurg]

Sodium benzoate is the exact same structure as benzoic acid, it's just that you have a sodium ion in place of the hydrogen ion. So in a sense, you still have the exact same problem with sodium benzoate as you do with benzoic acid.

[YT2095]

yeah, I`ve been studying up on it since, and basicly it`s just Not gunna happen, not unless I get some lithium alu hydride, and I don`t fancy my chances trying to synth some.

I`m giving it up as a bad idea anyway, even the benzene route is really tricky, the yeild is low and it comes out as a gas.

I`ve decided to work With the carboxyl group instead, maybe make a few esters, I also like the idea of making Benzocaine, I just gotta find a way to attatch an amine to #4 position in the benzene ring ?

nothing lost though, I`ve learned a little more

[woelen]

....then you can esterify your benzoic acid with some benzene...

Are you sure? Esterification is between an alcohol and an acid. So I can imagine esterification between phenol and benzoic acid, but not between benzene and benzoic acid.

 

R-OH + HO-(O)C-R' <---> R-O-(O)C-R' + H2O

 

The problem is that benzoic acid has a -COOH group attached to the benzene ring. You can reduce the -COOH group with a strong reductor like LiAlH4, but that still leaves the C atom on the benzene-ring.

 

I can imagine that making phenol from benzoic acid can best be done via the benzene route, by first taking off the -COOH group, then substituting one of the H's on the benzene ring (e.g. with Cl) and then replacing that with -OH. But I'm not an organiker, so there may be easier routes to phenol.

 

@YT: You know that benzene is a proven carcinogen? Please do not breathe the vapors from your hot NaOH/benzoic acid mix.

[YT2095]

@YT: You know that benzene is a proven carcinogen? Please do not breathe the vapors from your hot NaOH/benzoic acid mix.

 

Hmmm.. that`s a bit late. when I did it I saw the gas coming off, wated a little in my direction and Identified it as benzene (it`s a smell I don`t like and I rem it well), the rest I lowered the test tupe opening to the flame, and it burned down the tube in a second (sooty smoke), there was literaly on milligrams of the 2 ingredients to start with, so there was even less benzene. besides, I smoke about 30 a day anyway, it`s unlikely the few PPM of benzene will have a significant effect in comparison

 

as for the benzene and the benzoic acid combo, wouldn`t that stand a good chance of making the Anhydride of the acid?

I know for the ester it Needs the `OL` with the acid to work.

[jdurg]

My bad. I can't believe I goofed on that part there. It's been a rough week.

 

Anyway, the best method would be through the chlorobenzene route, or even the bromobenzene route as I believe bromine can substitue for chlorine in that step.

[woelen]

I figured Phenol was a good place to start as it`s quite simple and basic, and stores well as opposed to Benzene liquid

No, phenol is a real pain to store and to my opinion it is worse on storage than benzene. I have 100 ml of 80% phenol solution in water and it is a real pain. It is extremely corrosive to the skin. I had a single drop on my skin and rinsed it away immediately, but it gave a really nasty tinging feeling and strong irritation. The skin became white. The smell also is a real pain and sickening if you smell it all the time. Now I store my phenol in a double container:

 

Glass bottle with phenol, wrapped in a plastic food bag, put in a glass jar with a tight metal screw cap. Only with this type of storage, the smell is not coming out anymore.

 

The phenol also is very prone to oxidation and subsequent formation of condensation products. Pure phenol is colorless, but it quickly turns red/brown on storage, due to oxidation. The oxidation products condense to large molecules of varying composition and give a kind of brown crap.

 

I already have the phenol for several weeks now (I received it from a friend, with whom I exchanged some chemicals), but I still only did one experiment with it, due to its annoying properties.

 

An interesting chemical though is hydroquinone. It is used as a photo developer and can be purchased easily as the pure compound at many places. This is a phenolic compound. It is benzene with two -OH groups attached to the benzene ring, in para-positions. Hydroquinone does store well, has many of the chemical properties of phenol, but not its highly irritating odour and corrosivity towards the skin. It is an off-white water-soluble solid, which can be oxidized easily and forms interesting complexes with many metals. It can also serve as the basis for all kinds of organic chemistry experiments and is relatively safe. Just an idea ??

[YT2095]

lol, don`t worry about it, I`m doing that all the time

 

I could Possibly synth some of that, although I`ve not 100% perfected the benzene extraction het, I`m sure I`ll need to condense it quickly as I don`t want any gasses to escape, pity I only have 150 grams of this sodium benzoate, if I`m going to go to the trouble of making it work perfectly, it would be nice to scale it up and actualy have a decent amount of product for my efforts, 100ml would be nice!

anyway, Benzocaine and the likes, still keeping it as benzoic acid, How does one go about attatching to the other positions in the ring?

 

edit: Aha, we posted at same time, Woelen that sounds Ideal! I`ll have to get some of that