1,5-Hexadiene

1,5-Hexadiene is the organic compound with the formula (CH$2$)$2$(CH=CH$2$)$2$. It is a colorless, volatile liquid. It is used as a crosslinking agent and precursor to a variety of other compounds.

Synthesis
1,5-Hexadiene is produced commercially by the ethenolysis of 1,5-cyclooctadiene:
 * (CH$2$CH=CHCH$2$)$2$ +  2 CH$2$=CH$2$   →  2 (CH$2$)$2$CH=CH$2$

The catalyst is derived from Re$2$O$7$ on alumina.

A laboratory-scale preparation involves reductive coupling of allyl chloride using magnesium:
 * 2 ClCH$2$CH=CH$2$ +  Mg  →   (CH$2$)$2$(CH=CH$2$)$2$  +  MgCl$2$