Fluorescein Experiment

Introduction: One equivalent of an aromatic aldehyde, two equivalent of an ethyl acetoacetate, and one equivalent of ammonia on refluxing in an alcohol to give Hantzsch ester.

The first step, the condensation of acetoacetate with the aryl aldehyde,known as the Knoevenagel reaction. In the second step, the other half of the molecule can be assembled from ammonia and the second equivalent of acetoacetate; the product is an enamine, which is known as Stork enamine reaction. The third step is conjugate Michael addition and the final tautomerization have the driving force of a stable ring size and extended cross-conjugation in the final Hantzsch ester.

Reaction:

Procedure: Add 7.5 mL 40% formaldehyde to 0oC cooled 25.5 mL 0.2 mole ethyl acetoacetate

It can be prepared from phthalic anhydride and resorcinol in the presence of zinc chloride by the Friedel-Crafts reaction. Eosin is a fluorescent red dye produce by bromination of fluorescein. Reaction: Phthalic anhydride Resorcinol Fluorescein

Fluorescein Eosin

Procedure: Preparation of fluorescein Grind 1.5 g. Phthalic anhydride and 2.2 g. of resorcinol and heat the mixture in oil bath to 180°C. Meanwhile fuse 0.7 g of zinc chloride in china dish. Now add this powder ZnCl2 into the molten mass during the course of ten minutes using constant stirring. Transfer this solid in china dish and add 20 ml water and 1 ml conc. HCl and boil for 10 minutes. In this way the unchanged starting materials and the basic zinc salt are dissolved. Separate the fluorescein from the aqueous liquid by filtration, wash with water until the filtrate is no longer acid. Dissolve a particle of the preparation in a little ammonia and dilute in a beaker with one liter of water. Determine the weight and melting point of the solid. Calculate the % yield of the product. Obtain and interpret an infrared spectrum of the

Then add 0.8g NaOH to the cold Alclorite solution. Cool the NaOH/Alclorite solution to -10°C in the freezer. Grind 1.5 g phthalimide to a fine powder. Now add this to the cold (-10°C) Alclorite solution, plug the flask and mix with magnetic stirrer (or shake). The phthalimide will dissolve within 5 minutes. Place in the freezer again for at least 30 minutes. Now add the cold NaOH solution prepared above to the cold (not over +5°C) Alclorite solution. Allow to stand at room temperature until temperature reaches 20°C. Now heat to 80-85°C over 10 minutes and hold there for at least two minutes but not more than five. Cool in water to room temperature. Transfer the solution to a 100 mL beaker, keep some (~2-3 mL) in the Conical flask. Stir at medium speed on a magnetic stirrer. Now add 30% hydrochloric acid drop by drop till pH of the solution become 7 and filter it. Now add about 1.5 mL glacial acetic acid to this reaction mixture. Maintain temperature 200C or below and stir it. The anthranilic acid precipitated. Filter and dry it. Determine the weight and melting point of the solid. Calculate the % yield of the