fresher_007
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veratric acid
which is the best route for preparation of veratric acid????????
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JohnWW
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If you already have veratrole, it would be by some sort of oxidation, the reagent chosen depending on the functional groups to be considered.
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fresher_007
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i have veratrole......
but what will be the reagent
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not_important
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Veratrole is just 1,2-Dimethoxybenzene, you need to get a carbon on the ring at the 4- position.
You might do easier by oxidising vanillin to vanillc acid, and the methylating that; or methylating vanillin and oxidising it.
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fresher_007
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ok.....
i will try......
but any other route.... available......
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JohnWW
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Veratrole is 1,2-dimethoxybenzene, C6H4(OCH3)2, see http://en.wikipedia.org/wiki/1,2-Dimethoxybenzene. It is slightly soluble in water, but miscible in all organic solvents.
HOWEVER, despite the nomenclature, veratric acid, which is 3,4 dimethoxybenzoic acid, CANNOT be directly made from veratrole by oxidation; instead, it
has to be via "veratrole alcohol", which is 3,4-dimethoxybenzylalcohol, see http://en.wikipedia.org/wiki/Veratrole_alcohol , or veratraldehyde, which is 3,4-dimethoxybenzaldehyde, http://en.wikipedia.org/wiki/Veratraldehyde , or by some other suitable oxidizable substituted derivative of veratrole, and then by oxidation.
This would require a -CH2OH or -CHO or alkyl group to be added to the benzene ring, meta to one of the -OCH3 groups and para to the other.
A way of doing this, to obtain the aldehyde, appears to be by Friedel-Crafts acylation, using chloroformaldehyde, HClC=O, with usually AlCl3 or FeCl3,
in a polar organic solvent at about 80ºC:
C6H4(OCH3)2 + HClC=O ---[AlCl3]----> C6H3(OCH3)2CHO + HCl
However, HClC=O is likely to be, like COCl2, very volatile (probably a gas at reaction conditions) and highly poisonous, and not easy to come by or to
generate in situ.
Alternatively, and much more conveniently, an alkyl group, theoretically any such group, could be added by Friedel-Crafts alkylation, using any alkyl
chloride RCH2Cl:
C6H4(OCH3)2 + RCH2Cl ---[AlCl3]----> C6H3(OCH3)2CH2R + HCl
Then this product can be oxidized in high yield with KMnO4 to obtain veratric acid:
C6H3(OCH3)2CH2R ---[KMnO4--> CH3(OCH3)2COOH
Another problem is that some of the isomer with the -CHO or alkyl group ortho to one of the -OCH3 group is likely to be produced by the Friedel-Crafts
reaction, but it is not clear how much. The isomeric alkyl derivatives, or the acids, may require chromatographic separation. There is also the
possibility of more than one such -CHO or alkyl group being introduced to the ring.
[Edited on 12-3-10 by JohnWW]
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UnintentionalChaos
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Use vanillin. It's cheap, easy to get, and most of the work is already done.
5 seconds on google found this: http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv2...
A similar procedure is probably applicable with methyl iodide, methyl tosylate, or the methyl ethanesulfonate that we have a prep somewhere on this
forum for.
Oxidation of an aldehyde to a carboxylic acid is an easy transformation in the scheme of things. Most people would prefer to go the opposite direction
with such ease, I imagine. Any moderately strong oxidizing agent will do the job for you. Even bleach would probably be fine if that's really all that
you had.
JohnWWW- formyl chloride is unknown except under extreme conditions (and maybe not even then, it's been a while since I looked), IIRC. It prefers to
exist as a mixture of CO and HCl and is thus worthless for synthesis.
Due to sterics, FC acylation of o-dimethoxybenzene with methyl chloroformate would probably furnish the desired acid as the methyl ester. methyl
chloroformate is not quite as horrible as phosgene, but still not a walk in the park. Heavier alcohols would be even more advantageous to strap the
chloroformyl moiety to, decreasing volatility. Avoid tert-butyl as hydrolysis is rather more difficult.
[Edited on 3-12-10 by UnintentionalChaos]
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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entropy51
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Quote: Originally posted by UnintentionalChaos  | JohnWWW- formyl chloride is unknown except under extreme conditions (and maybe not even then, it's been a while since I looked), IIRC. It prefers to
exist as a mixture of CO and HCl and is thus worthless for synthesis.
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Well, it's not useless. It's the Gatterman aldehyde synthesis, wherein the aromatic hydrocarbon and AlCl3
is indeed gassed with CO and HCl. A modification uses zinc cyanide instead of CO. Only certain aromatics will react. No matter how you do them, they
are a pain in the tush.
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not_important
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And then there's chloromethylation, using HCl, formaldehyde, and a catalyst - ZnCl2 for benzene and toluene. Chloromethylether can be used instead,
as in The Chloromethylation of Veratrole
http://pubs.acs.org/doi/abs/10.1021/ja01170a508
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DJF90
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Formylation by Freidel crafts Acylation can be achieved by formyl fluoride or pehaps even formic-acetic anhydride. However I would expecct a
mix of two isomers to form. Friedel Crafts Alkylation is limited in so far as it's hard to control and generally gives a peralkylated product; I'd
expect this problem to be escalated by the fact that all of the unsubstituted positions on the ring are activated by the methoxy groups.
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smuv
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Methylation of eugenol followed by oxidation with chromic acid or permanganate is also an option
"Titanium tetrachloride…You sly temptress." --Walter Bishop
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