Determination of the relative reactivities of cis and trans isomers of b-bromostyrene towards polystyryllithium by Raman spectroscopy

The relative reactivities of cis and trans isomers of b-bromostyrene towards polystyryllithium have been determined by Raman spectroscopy. Polystyryllithium was prepared by the anionic polymerisation of styrene in cyclohexane using sec-butyllithium as initiator and subsequently reacted with mixtures of isomers of b-bromostyrene. The end groups of the resultant polymers were analysed by Raman spectroscopy in the spectral region 1550–1700 cm21 which contains the bands due to cis and trans n(CyC) stretching vibrations. The cis isomer of b-bromostyrene has been found to be about 14 times more reactive to polystyryllithium than the trans isomer which correlates well with theoretical predictions of lower stability for the cis isomer. q 2004 Elsevier B.V. All rights reserved.