pbmineral
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naphtalene to phthalic anhydride ?
Hi,
I've seen it was possible to get phthalic anhydride from naphtalene by oxidaton of one of the 2 benzene rings.
I'd like to do that vry simply. I've seen information with K permangate but don't know how to lead the experiment and the quantities to use. They also
advise to use alcaline solution of permanganate why ??
Waiting for your thoughts
Thanks
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not_important
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If you would use the site's search, and correct spelling, you would find the topic has come up before. For example
http://www.sciencemadness.org/talk/viewthread.php?tid=6573&a...
expect no further responses on this thread.
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DerAlte
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@ not_important – I feel you may have been unduly abrupt in your reply. Certain linguistic constructs in pbmineral’s make me suspect that English
is not his (her) first language (e,g. to lead from conduire = conduct). The error in the title of naphthalene may be a typo but that’s how it’s
pronounced in French. And I know, being new myself, how it takes time to feel your way around a new forum. I’ve made errors due to ineffective
searches and have replicated old info. The thread you suggested was a good one to read. PS – I tried to make a quote box but failed – what did I
do wrong? Tried to follow your instructions but didn’t work.
That said, one of my few masterpieces in organic chem. was the (successful) production of flourescein and eosin from naphthalene. I am not an organic
guy, and am amateur even at inorganic.
As far as memory can tell (this was 52 years ago!, when I was at college as an EE student, but done in my home lab) the initial step was the
conversion of naphthalene to (ortho) phthalic acid to the anhydride. It was done with fuming sulphuric acid (containing SO3) and a small bit of
mercury metal as catalyst. The temp involved was high, near the boiling point IIRC. Whether this was effectively an oxidation or a dehydration I am
not sure. SO2 and SO3 ( probably) were evolved. The main product seemed to be anhydride, IIRC. How I knew or purified escapes me, but it was a lengthy
process. To get fluorescein involved anhydride fusion with 1,3 dihydroxy benzene (resorcinol). Eosin (red) resulted from bromination.
Pbmineral specifically stated he wanted a simple process and suggested permanganate. I know of no such process but he has obviously read of one. All I
can suggest is that alkaline permanganate, being less potent an oxidant than in acid solution, avoids too drastic an oxidation of the naphthalene.
Also the product is reasonably acidic (ph ~2.5 first H, CRC) much more so than phenol or benzoic acid, other possible products of oxidation.
I believe I am correct in stating that in general naphthalene is considerably more reactive than benzene.
@pbmineral: Si vous etes, comme je crois, sur la plupart francophone, restez assure qu’ily a plusiers ici qui ne parle l’anglais assez bien que
vous! Votre anglais est mieux que mon francais. (Je regrette, pas d’accents ici.)
Regards,
DerAlte
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DerAlte
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A quick addendum. Search www.acros.com in the literature section. A very good synopsis of organic oxidations by permanganate can be found there – also Cr compounds and
much else.
Also, from Encyclopedia Britannica, 1945ed., PHTHALONIC acid (2-oxalobenzoic acid) is produced in Alkaline permanganate – for phthalic acid one
needs an acid solution… Again, I am no expert at organic.
Regards,
DerAlte
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