In the "Preparation of Benzene," Chromium states that benzene can be prepared in a dry distillation of a sodium benzoate with a strong base such as sodium
hydroxide. I can't identify the orange/yellow byproduct that Chromium and many others consistently notice when synthesizing benzene by this route.
The simple decarboxylation reaction at the bottom of this ChemGuide page cannot account for the orange/yellow byproduct, so it must be produced in a side reaction. This conclusion agrees nicely with
Chromium's observation that the amount of the byproduct is inversely proportional to the amount of benzene.
One plausible identity of the byproduct is sodium peroxide. It certainly has the proper color, and there is a source of sodium and oxygen. However,
this compound decomposes before it boils, so I can't imagine how any observable quantities would make it through the distillation setup. Any ideas or
links?Magpie - 13-5-2013 at 20:32
here's some earlier discussion of this yellow colored material:
Magpie, that link doesn't work... At least not for me. I get the error.
It's on p. 7 of the thread titled "Benzene synthesis"
by madscientist
[Edited on 14-5-2013 by Magpie]
[Edited on 14-5-2013 by Magpie]Organikum - 14-5-2013 at 09:45
Thats no "byproduct" but something what complexes with the benzene. At least thats my only explanaition. When I distilled directly into a dry flask I
got mainly this stinky stuff and almost no benzene, even not after washes and whatever.
When I distiled into water I got lots of benzene and the stink.
Redistillation yielded very clean and pure benzene.
Its in the named thread IIRC.
/ORGtomatl - 14-5-2013 at 17:01
Magpie, thank you for the link. I apologize for creating an unnecessary thread. I certainly tried searching the forum. Next time my search will be
more thorough.Boffis - 21-5-2013 at 05:51
No idea what the smelly stuff is but the yellow-orange colour could be due to anthraquinone which is surprisingly volatile and may pass over with the
benzene to a small extent but careful fractionation should resolve this contaminent. The anthraquinone is formed by dimerisation of the benzoic acid
at high temperatures or in the presence of such chemicals as conc sulphuric acid. I haven't tried this out with benzoic acid as I have access to
substancial amounts of anthraquinone but I have tried it with gallic acid to produce hexahydroxyanthraquinone.
Attached is page 159 from Chemistry of Anthraquinone,
If sodium benzoate is distilled without alkali present, will benzophenone form?
Also I want to ask - is there any difference between distillation of Ca organic acid salts and sodium salts for example? Can one distill acetone from
CH3COONa ?
[Edited on 23-6-2013 by papaya]papaya - 24-6-2013 at 13:03
but still got no clue on exact procedure, also don't want to deal with benzene, isn't it possible to reduce benzoic acid to phenol some way?
Didn't want to create a new topic, thank you.
[Edited on 24-6-2013 by papaya]12AX7 - 24-6-2013 at 19:46
What about biphenol? Pretty common byproduct from radical reactions (geez, I forget if decarboxylation even involves a radical).
Timpapaya - 24-6-2013 at 20:10
Do you mean biphenyl ? Don't know honestly, decomposed a little powder of Na benzoate on Al foil and it gave a suffocating smoke reminding burning
plastic to some extent. But lets concentrate on the second question about making phenol please, any ideas?papaya - 26-6-2013 at 12:53
Something from wikipedia (benzoic acid page)
"Benzoic acid is mainly consumed in the production of phenol by oxidative decarboxylation at 300−400 °C:[13]
C6H5CO2H + 1/2 O2 → C6H5OH + CO2
The temperature required can be lowered to 200 °C by the addition of catalytic amounts of copper(II) salts. "
200C seems easy, is there any lab scale procedure for this ?
