Synthesis of Luminol

Creating a chemiluminescent compound from 3-nitrophthalic acid

Organic Synthesis Professional (Lab) 120 min ~$30.00

Objective

Synthesize luminol (3-aminophthalhydrazide) and demonstrate its chemiluminescent reaction with hydrogen peroxide.

Background

Luminol is a chemiluminescent compound used in forensic science to detect trace amounts of blood. It is synthesized by reacting 3-nitrophthalic acid with hydrazine, followed by reduction of the nitro group with sodium dithionite. When oxidized by hydrogen peroxide in the presence of a catalyst, luminol emits blue light.

Safety Warnings

  • Hydrazine is toxic and a suspected carcinogen — handle with extreme care in fume hood
  • Sodium dithionite generates SO₂ — use in fume hood
  • NaOH is corrosive
  • Wear nitrile gloves and goggles throughout

Required PPE

goggles gloves lab_coat

Materials

  • 3-Nitrophthalic acid (1 g)
  • Hydrazine hydrate (10%) (3 mL)
    Toxic
  • Triethylene glycol (5 mL)
    High-boiling solvent
  • Sodium dithionite (Na₂S₂O₄) (3 g)
    Reducing agent
  • Sodium hydroxide (NaOH) (5 mL)
    10% solution
  • Hydrogen peroxide (H₂O₂) (10 mL)
    3% for chemiluminescence test
  • Potassium ferricyanide (0.1 g)
    Catalyst for glow test

Equipment

Round-bottom flask (50 mL) Reflux condenser Hot plate Buchner funnel Filter flask Darkened room Test tubes

Procedure

1

Dissolve 1 g 3-nitrophthalic acid in 5 mL triethylene glycol in the round-bottom flask. Heat to 100°C.

5 min Fume hood required
2

Add 3 mL of 10% hydrazine hydrate. Attach the reflux condenser and heat at 130-140°C for 30 minutes.

35 min Hydrazine is toxic — fume hood essential
3

Cool the mixture. Add 15 mL hot water and 3 mL 10% NaOH.

5 min
4

Add 3 g sodium dithionite to reduce the nitro group. Heat at 80°C for 10 minutes.

12 min SO₂ released — fume hood
5

Acidify the solution with glacial acetic acid until luminol precipitates.

5 min
6

Collect the luminol by vacuum filtration. Wash with cold water and dry.

10 min
7

Test chemiluminescence: dissolve a small amount of luminol in 5 mL of dilute NaOH. In a darkened room, add H₂O₂ and a trace of potassium ferricyanide.

5 min
8

Observe the blue glow. Record intensity and duration.

3 min

Expected Results

A pale yellow solid (luminol). When tested with H₂O₂ and ferricyanide catalyst in a dark room, an intense blue chemiluminescent glow should last for 15-30 seconds. The glow confirms successful synthesis.

Cleanup

Dispose of hydrazine waste in designated hazardous waste container. Neutralize acids and bases. Rinse all glassware thoroughly. Decontaminate work area.

Details

Category
Organic Synthesis
Difficulty
Professional (Lab)
Duration
120 min
Est. Cost
$30.00
Steps
8
Materials
7

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Frequently Asked Questions

What is the objective of Synthesis of Luminol?
Synthesize luminol (3-aminophthalhydrazide) and demonstrate its chemiluminescent reaction with hydrogen peroxide.
How difficult is Synthesis of Luminol?
This experiment is rated as Professional (Lab). It takes approximately 120 minutes to complete.
What safety precautions are needed for Synthesis of Luminol?
Key safety precautions include: Hydrazine is toxic and a suspected carcinogen — handle with extreme care in fume hood; Sodium dithionite generates SO₂ — use in fume hood; NaOH is corrosive.
What materials are needed for Synthesis of Luminol?
The main materials required are: 3-Nitrophthalic acid, Hydrazine hydrate (10%), Triethylene glycol, Sodium dithionite (Na₂S₂O₄), Sodium hydroxide (NaOH).
What results should I expect from Synthesis of Luminol?
A pale yellow solid (luminol). When tested with H₂O₂ and ferricyanide catalyst in a dark room, an intense blue chemiluminescent glow should last for 15-30 seconds. The glow confirms successful synthesis.