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Author: Subject: Heumann indigo synthesis help
mackolol
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[*] posted on 25-2-2019 at 08:27
Heumann indigo synthesis help


For quite a long time I'm struggling with synthesis of indigo dye. When I figured out that o benzaldehyde syntheses are nearly impossible for amateur chemist and very impractical I prepared anthranilic acid and purchased chloroacetic acid but unfortunately I don't have access to any references. Can somebody help me with paper describing synthesis of indigo in that way? Preferably heumann process as it seems to be the simplest (only naoh chloroacetic acid and anthranilic are used)
Thanks

[Edited on 25-2-2019 by mackolol]
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Waffles SS
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[*] posted on 25-2-2019 at 08:50



Quote:

To a 2-L flask equipped with a condenser were added 137 g anthranilic acid (1 mol),94.5 g chloroacetic acid (1 mol), and 1 L water; the mixture was heated for 3 h. On cooling,crystals of phenylglycine-o-carboxylic acid were separated out. These were filtered off and recrystallized from hot water to give∼1000 g of such acid.The mixture of 1 eq. phenylglycine-o-carboxylic acid, 3 eq. NaOH, and 1 eq. water was heated at 235–265◦C in the absence of air until the alkaline mass assumed an intense orange color, whereupon it was allowed to cool and subsequently dissolved in water. Passing a stream of air through the aqueous solution resulted in the precipitation of indigo. No yield was given


Heumann Indigo Process
https://doi.org/10.1002/9780470638859.conrr312


[Edited on 25-2-2019 by Waffles SS]




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mackolol
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[*] posted on 25-2-2019 at 09:33


Thank you very much Waffles
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NotBismuth
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[*] posted on 27-2-2019 at 23:42


Seeing that Chloroacetic Acid is considered an extremely hazardous substance, would it be possible to substitute MCA with Glacial Acetic Acid?
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Texium (zts16)
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[*] posted on 28-2-2019 at 05:36


No. If you draw out the reaction, you'll see why.



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Waffles SS
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[*] posted on 23-5-2019 at 07:54


Another example of Heumann indigo synthesis

44J9w.png - 344kB

But i am interested in Pfleger's synthesis of indigo and i want to know this is possible to use Sodium Methoxide or ethoxide instead of Sodium amide?

970px-Indigo_Synthesis_V.1.svg.jpg - 18kB

[Edited on 23-5-2019 by Waffles SS]




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