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Organic : 2-carboxyazobenzene
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 Message 1 of 5 in Discussion 
From: MSN NicknameX1095  (Original Message)Sent: 10/14/2005 2:01 AM
Hello

Does anybody know how to synthesize 2-carboxyazobenzene (a.k.a. p-phenylazobenzoic acid)? The method that is used for 4- and 3-carboxyazobenzoic acid does not work for the para version because of steric hindrance.

Thanks, X1095


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 Message 2 of 5 in Discussion 
From: MSN Nickname·Steve·Sent: 10/14/2005 7:01 AM
This would be o-phenylazobenzoic acid?  The ortho isomer of Ph-N=N-Ph-COOH if I understand correctly.  A possible strategy is hinted on an organic review page at http://www.wpbschoolhouse.btinternet.co.uk/page07/Aromatics.htm.  It mentions that the diazonium chloride can be formed from 2-aminobenzoic acid.  Coupling of this diazonium salt with aniline should give 2-(p-aminophenylazo)benzoic acid.  Then perhaps the aniline NH2 group can be removed by subsequent diazotization and treatment with H3PO2 without affecting the azo and carboxy groups.  Just a guess!  I'm not familar with the methods used to prepare the other isomers.

Steve

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 Message 3 of 5 in Discussion 
From: MSN Nickname·Steve·Sent: 10/14/2005 7:11 AM
(I mean the ortho isomer of Ph-N=N-C6H4-COOH, writing this a little more clearly.)

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 Message 4 of 5 in Discussion 
From: MSN NicknameX1095Sent: 10/16/2005 3:15 AM
Yes, of course, o-phenylazobenzoic acid. My apologies.

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 Message 5 of 5 in Discussion 
From: MSN NicknameX1095Sent: 10/16/2005 3:22 AM
Thanks, Steve. I'll look into it, although I'm afraid that steric hindrance will interrupt the reaction again.

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