This preparation is an example of Schiff base formation leading to an aromatic compound. The reactio — Organic Chemistry Chemistry Question

This preparation is an example of Schiff base formation leading to an aromatic compound. The reaction scheme for the preparation of 2,5-diphenylquinoxaline is as follows:

[VISUAL]

Chemicals
- Benzyl, 240 mg,
- 1,2-diaminobenzene, 250 mg,
- Methanol,
- Water.

Procedure
Benzil (240 mg) and and 216 mg of 1,2-diaminobenzene (ortho-phenylenediamine) are mixed in a regular test tube and the mixture is heated in a hot water bath for 20 minutes. The mixture will first melt and then change into a light tan-coloured solid. The solid is dissolved in hot methanol (ca 10 cm 3 ) and the solution is left undisturbed until crystallization starts. If crystallization fails to start, reheat the solution and add small amount of water using a Pasteur pipette to the point of turbidity. Crystallization will then begin and will be completed on cooling to ambient temperature. The crystals should be filtered off as soon as they are formed, otherwise brown oxidation by-product may accumulate on standing too long. The product should appear as colourless needles. Weigh the product, calculate the yield and determine the melting point.

Record the following data:
1. The mass of the product.
2. The yield of product as percentage of the theoretical yield. (Show your calculation.)
3. The appearance and colour of your product.
4. The meting point.

Note: The starting material 1,2-diaminobenzeneis often coloured and its purification by sublimation prior to this experiment may be necessary.