1,4-Cyclohexadiene

1,4-Cyclohexadiene is a highly flammable cycloalkene that occurs as a colorless clear liquid.

1,4-Cyclohexadiene and related compounds may be prepared from benzene using lithium or sodium in liquid ammonia, this process being known as a Birch reduction. However 1,4-cyclohexadiene is easily oxidised to benzene, the driving force being the formation of an aromatic ring. The conversion to an aromatic system may be performed in the laboratory using an alkene such as styrene, along with a hydrogen transfer agent such as palladium metal supported on charcoal.

γ-Terpinene is a naturally occurring derivative of 1,4-cyclohexadiene, found in the essential oils of coriander, lemon, and cumin.