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Author: Subject: Benzene synthesis
madscientist
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[*] posted on 28-11-2002 at 17:40
Benzene synthesis


Synthesis of benzene seems to be a topic of interest and value, considering that benzene has now been labeled as an "evil scary carcinogen of inevitable death".

There's several routes that come to mind. First, is a Friedel-Crafts reaction that Osmonium suggested: AlCl3 will catalyze the conversion of toluene into benzene and mesitylene. A second route would be decarboxylating benzoic acid by strongly heating it. A third route would be reacting 1,3,5-trichlorocyclohexane with a strong base. And a fourth route, which I am not completely certain would work, would be aldol condensation - involving adding a strong base to acetaldehyde, which should catalyze conversion into benzene.

Any thoughts?




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shocked.gif posted on 28-11-2002 at 18:55


Do you have more information on the decarboxylation of benzoic acid?
Decomposition temp. and similar things?

I think the decarboxylation of benzoic acid would be very attractive for the home chemist due to the widespread use of benzoic acid in the food industry, and therefor it should be easy to get and not that expensive.
I still have some 100-200g of benzoic acid from a drug store.

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[*] posted on 28-11-2002 at 19:19


I do not know at what temperature benzoic acid decarboxylates. If I remember correctly, salicylic acid decarboxylates at a tad above 200C, so I suppose that benzoic acid would decarboxylate at a temperature somewhere above 200C.

On a side note, is anyone aware of any sources of any cyclohexanes, especially 1,3,5-trichlorocyclohexane?




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[*] posted on 29-11-2002 at 08:27


If I remeber right, it does'nt have to be benzoic acid, the sodium salt will do. Mix it with waterfree sodium carbonate and heat it gently. Benzene will distill over. You can also have some sand mixed in to have a more "smooth" reaction.
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[*] posted on 29-11-2002 at 09:15
sodium benzoate instead of benzoid acid


Yes, benzene is an interesting subject.
I think I remember that I saw an experiment in a basic experimental chemistry book which advised to react benzoic acid with sodium hydroxide at first and decomposing the resulting sodium benzoate by heating it.

Madscientist, do you have further information about toluene / AlCl3?
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[*] posted on 29-11-2002 at 14:13
Benzene from tolulene


if i recall correctly megalomania mentioned that he was working on a synthesis route for benzene from tolulene using KMnO4 to oxidize it. Using KMnO4 has the advantage of being fairly easily found OTC or it too can be made from OTC chemicals. I don't think he ever published this route completely but refered to it in a thread on E&W about KMnO4 synthesis.
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[*] posted on 29-11-2002 at 14:44


He was probably thinking of benzoic acid decarboxylation, then. The KMnO4 would be used to oxidize the toluene to benzoic acid.
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[*] posted on 2-12-2002 at 15:02


It seems that this reaction would work.

NaC6H5COO + NaOH --(heat)--> Na2CO3 + C6H6

I haven't any more information on preparing benzene from toluene and aluminum trichloride.




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[*] posted on 2-12-2002 at 17:04
hmmm


Quote:
It seems that this reaction would work.

NaC6H5COO + NaOH --(heat)--> Na2CO3 + C6H6


That seems reasonable. Calcium hydroxide might be preferrable, since it won't fuse very easily and is cheaper. One could presumably use other aromatic carboxylic acids, such as phthalic acid. That's not a major improvement, but one could start with the slightly-more-common xylene instead of toluene. Another improvement would be finding an alternative to KMnO4 for the oxidation; its availability and price vary to much to always suggest it.
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[*] posted on 6-12-2002 at 13:50


Permanganates can always be recycled though, which is a big advantage.
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[*] posted on 6-12-2002 at 20:53


Recycled? What method did you have in mind? I've seen electrochemical syntheses of permanganates, and ones that use fused oxidizers + MnO2. Neither method is exactly a recycling in my book...
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[*] posted on 13-12-2002 at 16:27


Potassium permanganate is available as a cleaner for water softeners. I purchase it at a home improvement store for $15.00 per 5 lbs. It seems to be of a reasonably good purity.
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[*] posted on 4-2-2003 at 12:14


Hi there,

The following might also work to gain benzene. Try to protonate phenol and heat it. Probably the benzene will lose the water. What do you guys think. I never tried it before.

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[*] posted on 7-3-2003 at 07:12


Sorry to dig-up an old post but i found that during search on Furan and Pyrrole Ring and it said (vaguely) that Benzoic Acid can be Decarboxyled by heat and the addition of Calcium Oxide (CaO) wich is Lime....

If the link intereset you: http://www.cem.msu.edu/~reusch/VirtualText/react3.htm
but it doesn't say much about quantities...

Edit: Url bogus

[Edited on 7-3-2003 by Blind Angel]




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[*] posted on 25-3-2003 at 12:45


I seem to be bad at replying, sorry Polverone.

MnO2 can be fused with hydroxide, and this will air oxidise to Manganate(VI), acidify and it disproportionates to manganate(VII) and MnO2.

I'm very interested in the production of benzene from acetone, the main step being cyclisation with sulphuric acid to sym trimethylbenzene. Outside of industrial conditions this is only 25% yeild though.
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[*] posted on 26-3-2003 at 06:33


i´m quite interested too in the production of bencene from acetone, if you know something else please let me know thanks!:)
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[*] posted on 26-3-2003 at 07:41


Even trimethylbenzene/mesitylene could be useful after some careful nitration to TNTMB. I would expect slightly more power and slightly higher density than trinitronapthalene, which is intermediate in power to DNB and DNT. Not very strong, but would be good with a bit of AN. I'll see what I can find out about making mesitylene from acetone...

Hmm, just remembered something. I think I remember someone saying that nitration of mesitylene is/can be dangerous. In that case oxidising it to 3,5-dimethylbenzoic acid before nitration will help the nitration go nice and calmly. It would probably decarboxylate either during the reaction, or afterwards if you boil it in water, to give TNm-xylene, and from there further oxidations/decarboxylations will lead to TNT then TNB.
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[*] posted on 26-3-2003 at 13:23


The third nitration of mesitylene is what makes it dangerous - it must not be conducted at elevated temperatures, or an explosion may result.



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[*] posted on 27-3-2003 at 10:25


Initial report of formation of mesitylene from acetone and sulphuric acid.
KANE, J. prakt. Chem. [l], 15, 131 (1838).

Investigation of maximum yeild (27%)
V. E. TISHCHENKO and L. I. ANTZUS, Zh. prikl. khim. 4, 806 (1931).

Using HCl at 100 atmospheres 36% Yeild,
V. IPATIYEV, B. DOLGOV and J. VOLNOR, Ber. 63, 3072 (1930).

Using HCl, sealed tubes, 145 to 195C up to 47% yeild.
E. SUCHARDA and H. KUCZYNSKI, Roczniki Chem. 14, 1182 (1934)

If anyone has access to a university library, Id be very interested to read these myself.

No prizes for guessing where these refs come from,
It does also state that explosive power of trinitromesitylene is about the same as DNT, but the sensitivity to impact is high, about the same as TNX, probably becuase of the high substitution of the ring.

One of my older organic chemistry books simply states that benzene can be made by distilling 1 part of benzoic acid with 2 parts lime, though its unclear if this is refering to quicklime or slaked lime. I suspect a little extra water in the mixture would not hurt. If the amount of benzoic acid is too high, or if calcium benzoate is used on its own then it forms benzophenone instead (from memory).

From mesitylene the toluene process seems like it would work just as well, alkaline permanganate oxidation (for example) followed by distillation with x6 (or x4 depending on how it scales) of lime.

Nice the edit feature works now.

[Edited on 27-3-2003 by Marvin]
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[*] posted on 30-3-2003 at 12:12


Benzene by reverse Friedl-Crafts acetylation from toluene with AlCl3 or better AlI3 and a efficient column with very high reflux/distill ratio (suggested 500/1).
Practical: Toss a lot Al foil in a flask add toluene and I2 and distill.
(Rhodium and Osmium merits)


from gasoline by distillation usng a "Podbielniak still" whatever this maybe. Someone a idea?
(Osmium and lugh merits)
here is to add that it is told that aviation fuel for the Cessnas contains much more benzene which is so easier to distill also.


Benzene from benzoic acid.
patents:
DE 936,036 (1952)
DE 958,920 (1956)
(I can upload these to the FTP if requested)

The mentioned process of heating benzoic acid with lime/NaOH seems to be problematic was told. At least a copper catalyst is needed (copper/cupric sulfate) and the temperatures needed are very high so there are reasonable problems to catch and condense the produced benzene.


Benzene from acetylene, see the attached file please.
(200°C, Cr/Al catalyst, high yields and purity)

hope this helps
ORG

Attachment: acetylene _to_benzene.pdf (354kB)
This file has been downloaded 3133 times

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[*] posted on 3-5-2003 at 06:30


i atualy saw the benzene from acetylene a few years ago in a kiddy chemistry book i have(a thing one with lots of pics). sometimes those little books have some cool reactions

also, i woudl ike to make some benzene, i was thinking about ttakeing some Al and putting it in a flask and heat it as i pump chlorine in that was generated by HCl + KMnO4 ---> through tube or something that has prilled CaCl2 to dry and then reflux the anhydrouse AlCl3 with toluene and distill off the benzene

is this good?

[Edited on 5/4/03 by Madog]




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[*] posted on 3-5-2003 at 19:31


The following reaction caught my eye;

7.CO + 6.CH4 ==(AlCl3)==> C6H6 + C6H5-CH3 + 15/2.H2O

This is an experimental process for the conversion of synthesis gas and methane to benzene and toluene. Synthesis gas can be made one of two ways;

  • super high pressure controlled oxidation,


  • leading steam over hot carbon in the absence of air


  • I would say the second would be of interest to the amateur chemist. :)

    I'm sure that with a little invention and some piping, this could be pulled off.




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    [*] posted on 6-5-2003 at 11:08
    Zinc + phenol


    another possibility:

    When the vapours of Phenol are passed over red-hot zinc dust, then reduction takes place, as a result benzene is formed.

    C6H5OH + Zn ® C6H6 + Zn0

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    [*] posted on 21-5-2003 at 23:47
    Chloramin-B


    I stumbled over a fragment where was mentioned theat benzene can be made very easily from Chloramin-B (B stands for the benzenering).
    Formula: C6H5SO2NNaCl
    By heating (if a catalyst has to be present wasn´t mentioned, a fragment, as told...)

    As Chloramin-B is readily available for water desinfection this could be a very interesting way to benzene so it works.




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    [*] posted on 22-5-2003 at 10:46
    threads


    I was searching some time back and came up with these sites- the temperature seems to be the stumbling block.

    http://www.orica.com/resource/chemfact/pdffiles/benzene.pdf

    http://web.mit.edu/10.551/www/Archives/Project97.1.pdf

    Is this do-able?
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