STOPPED-FLOW INVESTIGATION OF THE CATIONIC OLIGOMERIZATION OF TRANS-1,3-DIPHENYL-1-BUTENE INITIATED BY TRIFLUOROMETHANESULFONIC ACID IN DICHLOROMETHANE

Reaction of trans 1,3-diphenyl-1-butene (D), the trans ethylenic dimer of styrene, with trifluoromethanesulfonic acid in dichloromethane has been performed at temperatures lower than room temperature using a st opped-flow technique with real time UV-visible spectroscopic detection . The main product of the reaction was the indanic dimer of D. A trans ient absorption at 340 nm has been assigned to 1,3-diphenylbutylium, a model for the polystyryl cation. Other absorptions at 349 nm and 505 nm have also been observed and were assigned to an allylic cation, 1,3 -diphenyl-1-buten-3-ylium, resulting from hydride abstraction from D. This species was very stable at temperatures lower than -30 degrees C. A general mechanism was proposed based on a kinetic study of the invo lved reactions.