Aqua-regia1
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o-nitroaniline by orthoselektive nitration from acetanilide or sulfanilic acid
Does someone know how to nitrate (and then separate the two isomers) acetanilide or sulfanilic acid to become o- nitroaniline ? Vogel and orgsyn
dont have a description. I have plenty of both precursors. I take it that the nitration goes without H2SO4, to eliminate the formation of p-isomers.
(Solvent: Acetic anhydride+glac. acetic acid?) Thank"s!!
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DJF90
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From my perspective, starting with acetanilide and nitrating this should yieild both the ortho and para isomers (as the amide group is electron
donating when joined to the aryl ring via the nitrogen atom). This mixture of isomers can then be hydrolysed (amide=> amine) and fractionally
distilled under reduced pressure to avoid decomposition. Under atmospheric pressure, o-nitroaniline boils at 284C (decomposes), whereas p-nitroaniline
boils at 332C (not sure about decomposition here). I was able to put together this rough outline of a synthesis (which I hope is a valid route) using
just google to find the required information. Reagents and conditions could maybe be provided by other members, but I believe experimentation is the
best way here.
Why would not using H2SO4 during the nitration eliminate the formation of the p-isomer?
EDIT: Just looked at the wikipedia page for p-nitroaniline, and there is a reaction scheme using the mixed acids for the nitration of acetanilide, and
acetic acid for what I presume to be a solvent. It also says "After this reaction, a separation must be performed to remove 2-nitroaniline, which is
also formed in a small amount during the reaction". That is the isomer that is wanted though 
[Edited on 28-9-2008 by DJF90]
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Aqua-regia1
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If you nitrate acetanilide with 100% nitric acid without H2SO4 in dry 50-50% acetic acid+ acetic anhydride solvent mixture, issues in situ
acetyl-nitrate. By this agent produces over 90% yield the 2- isomer. The remains are 4, and slight 2,6 isomers.
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DJF90
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Are there not any 3 isomer produced?
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Nicodem
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Most examples of acetanilide nitration in literature report a para/ortho regioselectivity of 4 to 5. There are a couple of exotic methods published
which claim higher ortho regioselectivity (for example: Tetrahedron, 57 (2001) 1793-1799; J. Org. Chem., 60 (1995) 3445-3447;
J. Chem. Soc., Perkin 1 (1995) 339-343; J. Chem. Soc., Perkin 1 (1998) 1589-1590).
The preparation of o-nitroaniline from sulfanilic acid is described in Berichte der Deutschen Chemischen Gesellschaft [Abteilung] B: Abhandlungen,
58B (1925) 2286-2288 (DOI: 10.1002/cber.19250581008):
| Quote: | Abstract
Anhyd. sulfanilic acid (173 g.) dissolved with the aid of 69 g. K2CO3 is treated at 50 with 112 g. Ac2O at such a rate that the temp. is kept at
65-70; on standing in the cold for several hrs. the soln. deposits 230 g. K acetylsulfanilate (the mother liquors yield another 22 g. on concn.). The
salt (506 g.) is slowly added to 1500 g. H2SO4 (66 B.acte.e.) and treated dropwise at 5 with 150 g. of 85% HNO3 and 150 g. H2SO4 (66 B.acte.e.),
stirred 3-4 hrs., allowed to stand overnight, poured in a thin stream upon 7 kg. ice, treated with 138 g. K2CO3, neutralized with marble, boiled,
filtered hot, concd. over a free flame and treated with KCl, giving 550 g. 2,4-O2N(AcNH)C6H8SO8K, 299 g. of which, refluxed 1 hr. in 1500 cc. of 67%
H2SO4, and poured into ice H2O yields 110 g. o-O2NC8H4NH2. |
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Aqua-regia1
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Thank you Nikodem. Can you send me this german article? I dont have acces to Wiley (I speak german very well)
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Sauron
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Just go to References, Wanted References thread, and request the Ber. article using the information Nicodem provided. Don't forget to include the DOI.
If you don't have References PW it's a good time to ask for it.
This prep is described in Fundamental of Dye Chemistry in forum library downloadable for free.
Various parts of the sequence are in Org.Syn., Vogel, etc. It is not a tough prep and does not require heroic nitration conditions like 100% HNO3 and
Ac2O. Ordinary mixed acid will work fine with the 4-position blocked, removing the sulfonic acid group is trivial as is removal of the N-acetyl.
Sic gorgeamus a los subjectatus nunc.
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Aqua-regia1
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Ok, I know it. Thank you. But the german paper can't dowloading. Maybe I am too stupid.
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