MODEL COINITIATION REACTION IN CATIONIC P OLYMERIZATION - ANALYSIS OFTHE REACTION-PRODUCTS OF TICL4 WITH 2-ISOTHIOCYANO-2,4,4-TRIMETHYLPENTANE

The reaction of TiCl4, with 2-isothiocyano-2,4,4-trimethylpentane (ITP ) was studied at -50 degrees in CH2Cl2. The products were analysed by various techniques: gas phase chromatography coupled with mass spectro metry using either electronic impact or chemical ionization modes, pro ton NMR spectroscopy at 300 MHz and i.r. spectroscopy. It is shown tha t ITP is ionized and that 2-chloro-2,4,4-trimethylpentane and 2-thiocy ano-2,4,4-trimethylpentane are produced. Elimination reactions are als o observed leading to the in situ production of 2,4,4-trimethylpentene which can furtherly react with ionized ITP. The structure of the addi tion products does not correspond to the classical initiation reaction . This finding is qualitatively explained by the stabilization effect of the pseudohalide containing counteranion on the carbenium ion resul ting from ionization, combined to steric hindrance of the olefinic sub strate.