Fresh Cyclopentadiene for Diels-Alder

During the next two weeks our students are doing at our Teaching Labs one of the classic reactions in Organic Chemistry, the Diels-Alder reaction. So I had some fun distilling cyclopentadiene from dicyclopentadoene for more than 100 students.

I’m including a protocol to obtain  ~150 mL (2-3 horas of distillation)

The reaction apparatus is assembled by attaching a thermometer, Vigreaux distilling column and a long Liebig condenser to a 500 mL two necked flask.  The receiver is cooled with an ice-water bath (00C) . Dicyclopentadiene (~250 mL) is placed in the two necked flask and heated to about 160°C with an electric heating mantle or oil bath. Thermal decomposition begins at about 150°C and distillates at 38 ~ 46°C can be obtained . Heating is applied slowly, because rapid temperature increases cause dicyclopentadiene to distill prior to undergoing thermal decomposition. In such a case, re-distillation allows narrow boiling-point distillates. Distillation took around 3 hours.The cyclopentadiene was collected at 00C and  was stored at -200C for at least one week.

Cyclopentadiene dimerizes rapidly at room temperature and should be used immediately.

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