[Luminol's Synthesis]


Be sure all flammable solvents are removed from the fume hood before beginning this experiment.

On a steam bath, heat a flask containing 15 mL of water. Place 1 g of 3-nitrophthalic acid and 2 mL of an 8% aqueous solution of hydrazine (toxic! cancer suspect agent) in a 20 x 150 mm side-arm test tube.

Heat the mixture at an angle over a Bunsen burner flame (hold the test tube in a clamp) until the solid is dissolved. Turn off the burner, add 3 mL of triethylene glycol and clamp the tube in a vertical position above the burner.

Add a boiling chip and insert a thermometer through the rubber part of a thermometer adapter placed on a neoprene adapter in the mouth of the test tube as shown in the diagram on the next page. Position the bulb such that it is immersed in the middle of the liquid and not touching the sides or bottom of the test tube. Connect the side-arm to the vacuum outlet. Open the valve and using the Bunsen burner, boil the solution vigorously under vacuum to evaporate the excess water (110-130).

After the water has been removed, the temperature will increase rapidly over 3 to 4 minutes until it reaches 215. At this point, the Bunsen burner should be used to warm the test tube intermittently, keeping the temperature at 215-220 for 2 minutes.

Allow the reaction mixture to cool to about 100C, then add the 15 mL of hot water. Cool the tube under running water, and collect the solid nitro compound on a Buchner funnel. [Note: The solid is obtained in a more easily filterable form if hot water is added followed by cooling, rather than if cold water is simply added.] You may use an ice bath to aid in the crystallization.

Place the moist nitro compound back into the uncleaned side-arm test tube in which it was prepared. Add 5 mL of 3 M sodium hydroxide solution and stir with a glass rod. Add 3 g of fresh sodium dithionite, washing the solid down the walls with a little water. Heat the mixture over a Bunsen burner until it boils. Continue to heat with stirring for 5 minutes. Add 2 mL of acetic acid, cool under running water, then on ice. Stir the mixture and collect the solid luminol by vacuum filtration.

[Luminol's Synthesis]