Abstract: An alkene is coupled with an aromatic hydrocarbon having an active hydrogen on a saturated alpha-carbon in the presence of an unsupported alkali metal as a catalyst under high shear agitation conditions. In preferred embodiments of the invention, the alkene is an alkene of 2-20 carbons, such as ethene or propene; the active hydrogen-containing aromatic hydrocarbon is an alkyl-benzene, such as toluene; the alkali metal is potassium or a potassium alloy; and the high shear agitation conditions are attained by operating a turbine-type impeller at a tip speed of at least about 5 m/sec.