I am going to perform the synthesis of indigo via Heumann's methods which uses anthranilic or aniline as a starting materials. I am looking for the indigo synthesis procedure which includes all chemicals and the amounts needed but hopeless to find one.

Can anyone help me ?


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Synthesis of indigo: In place of anthranilic acid or aniline, you can simply use 2-nitrobenzaldehyde (see: Baeyer–Drewson indigo synthesis). For the mechanism of the reaction see: WIKIPEDIA.

Method: Place about $\pu{0.1 g (\pu{100 mg})}$ of 2-nitrobenzaldehyde solid into a test tube and, using a $10$-$\mathrm{mL}$ graduated cylinder, add $\pu{2 mL}$ of reagent acetone to the test tube. Swirl the tube to dissolve the solid completely. Now, add $25$ drops of distilled water to the acetone solution, and swirl again gently. Then, slowly add $15$ drops of $\pu{3.0 M \ce {NaOH}}$ solution. Your solution should rapidly darken and a deep purple solid (indigo) should precipitate from the solution. Place the test tube in a rack to stand until precipitation completed. Filter the solution using a Büchner funnel ($30$-$\mathrm{mL}$) and a filter flask ($125$-$\mathrm{mL}$). Wash the solid with distilled water several times until no more color washes from the solid, and finally by two portions of $95\%$ ethanol.

Also see: http://slb.faculty.arizona.edu/sites/slb.faculty.arizona.edu/files/152/Indigo1.pdf


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