Question

Construct a flow chart on the production and isolation of diphenylacetylene, starting from 1,2-dibromo-1,2-diphenylethane, KOH and ethylene glycol

Answer 1

1. Take 200 mg (1,2- dibromo-1,2-diphenylethane) in a 10 ml pear shaped flask.

2. Add 1 ml Triethylene glycol

3. Add 1 pellet of KOH.

4. Prepare a sand bath with a thermometer.

5. As temperature of sand bath reaches 185-190 degree celcius.

6. Place the flask in the sand bath for 1-2 minutes.

7. Remove the flask as it turns dark brown.

8. Again place the flask on sand bath for 5 minutes.

9. Now remove the flask and cool for few minutes with air.

10. Now give a ice bath for 5 minutes.

11. Add 6 ml water & stir.

12. Filter by suction with a small hirsch funnel.

13. Rinse 2-3 times with water (2-3 ml).

14. Allow the diphenylacetylene formed to suck dry for few minutes.

15. Air dry to give brownish but largely crystalline crude product.

16. Product can be recrystallized by 95% methanol to get off-white tan crystals.