Synthesis of Indigo

This is based on Nile Red's Video Of Indigo Synthesis and some of my inference
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(Step 1 of the traffic light experiment)

Material:

1)    Acetone

2)    Diethyl ether

3)    NaOH

4)    2-Nitrobenzaldehyde

5)    Ethanol (95%)

Prepare 1M of NaOH

Prepare solution of 2-Nitrobenzaldehyde with acetone first. Then after stirring, add water of equal amount (Cloudiness Expected to happen)

Add the NaOH slowly to solution

Baeyer–Drewson indigo synthesis:

Note: Due to Presences of Na⁺ ions, Reaction:

CH₃COOH+Na⁺⇌CH₃COO^(-)Na⁽⁺⁾+H⁺

Add acetone as reaction takes place

Note: Reaction is Exothermic

After this put solution in Ice Bath and let it cool and stir

After this Gravity filter through filter paper

Note: To make filtration fast, one can use a vacuum filter

It is then washed with little distilled water

After water goes through

Use Ethanol to wash again, then repeat with diethyl ether

Then leave for a day to dry of any excess solvent

Final Product: Indigo

Synthesis of Indigo Carmine

(Part 2 of the traffic light experiment)

Materials:

1)    Indigo

2)    Conc. H₂SO₄

3)    Non-Iodized Salt

Dissolve Indigo in conc. H₂SO₄

Then place in a boiling water bath at 70℃-90℃ but preferably 85℃ to 80℃

Wait for about 30 minutes

Pour Solution to cold water

Filter solution and wash with water

Then to solution excess of NaCl is added

2NaCl(aq)+H₂SO₄(aq)àNa₂SO₄+2HCl

Due to common ion effect:

Indigo Carmine precipitates out of solution

Filter solution through Filter paper and wash with as little water as possible

Its is then leave it to dry

When it turns into a slimy form, put it to a bowl for crystallization

The Traffic Light Experiment and a variation

Materials:

1)    Glucose(Dextrose)

2)    NaOH

3)    Indigo Carmine

4)    Na₂CO₃

Traffic Light Experiment

First prepare a solution of NaOH and Glucose

Then the solution Indigo Carmine solution is made

Note: Only a little Indigo is required

The 2 Solutions are mixed

Note: Indigo Carmine Yellow Form has weak documentation no resource I could find

Variation:

To near boiling water add Na₂CO₃ and Glucose

And prepare indigo carmine solution is made

Due to Sodium Carbonate low pH, it does through more colour change and it is more gradual

Sources:

1)  https://www.youtube.com/watch?v=6yhR242MnwA

2)  https://www.youtube.com/watch?v=jBZ8ly4erzs

3)  https://patents.google.com/patent/WO2017093866A2/en :Example 3,4

4)  https://www.youtube.com/watch?v=1ueSa6-UqYo

Best Path Taken:

1)  Indigo Preparation:

1)  5g of NaOH add to 125mL of Distilled Water

2)  25g of 2-Nitro Benzaldehyde and 250mL of Acetone

3)  250mL of Water added

4)  Add NaOH solution

2)  Indigo Carmine Preparation:

1)  30mL of Conc. H₂SO₄ and 2.5g of Indigo

2)  Boil at 80-85℃

3)  Follow steps and add 30g of Non-Iodized Salt

3)  Traffic Light Experiment:

1)  150mL of Water, add 3g of Glucose and 5g of NaOH

2)  100mL of Water and 20mg of Indigo Carmine

3)  Solution added to Carmine solution

4)  Variation:

1)8g of Na₂CO₃ and 3g of Glucose and dissolve all of this in 150mL of boiling water

2)100mL of Water and 15mg of Indigo Carmine

3) Solution added to Carmine solution

Notes:

In my preparation, I wasn't able to cool due to my school not having a fridge nor ice so putting in water does work granted the yield is very very bad.

My final yield on my attempts for Part 1 were 3.8% and 44.8% by weight