Tandem GC/MS: A useful tool for studying end‐capping reactions of oligo(styryl)lithium anions

Anionic living polymerization methods, using organometallic initiators such as butyllithium reagents, have proven useful for, inter alia, styrene polymerization and are amenable to subsequent functionalization of poly(styryl)lithium in the termination step. In this study, general methods for the selective preparation of small styrene oligomers and termination of the intermediate oligo(styryl)lithium anions were investigated. The crude reaction mixtures were analyzed directly by tandem gas chromatography/mass spectrometry (GC/MS). Of the carbon‐ and silicon‐based electrophiles tested, chloro(chloroalkyl)silanes, Cl‐SiR₂(CH₂)_nCl in particular, were shown by GC/MS to be regioselective end‐capping reagents, thus allowing subsequent transformation to the primary amine. The combined GC/MS data allow not only an estimate of the degree of functionalization, but also the identification of by‐products, thus providing insight into the end‐capping process that otherwise might be difficult to access. © 1995 John Wiley & Sons, Inc.