isopropenyl

Isopropenyl is a three-carbon alkenyl substituent derived from propene. Its structural formula is CH2=C(CH3)-, and it is attached to a parent molecule through the CH2 end of the double bond. In systematic nomenclature it is often called 1-methylethenyl (or propen-2-yl). The group is commonly encountered in organic synthesis as a reactive vinylidene substituent that conveys a double bond and a methyl substituent to the rest of the molecule.

Isopropenyl groups occur in a variety of derivatives, including isopropenyl esters and isopropenyl aryl compounds. A well-known example is isopropenyl acetate, used as an acetylating agent and as a monomer unit in certain polymers. Isopropenyl benzene, also called alpha-methyl styrene, is used as a monomer for specialty polymers.

Reactivity and properties: As an alkene, the isopropenyl group participates in typical alkene reactions, including electrophilic addition and radical polymerization. Because of the terminal vinylidene motif, derivatives can undergo polymerization or addition reactions at the double bond, and the group can be introduced or removed by standard organic synthesis methods to yield esters, ethers, or substituted hydrocarbons.

See also: vinyl group, allyl group, propenyl.