Kinetics and mechanism for the phase transfer catalyzed cycloaddition of dichlorocarbene to <i>cis</i>‐1,4‐polybutadiene

Abstract

Abstract The kinetics for the cycloaddition of dichlorocarbene to cis ‐1,4‐polybutadiene (BR) have been examined for aqueous and solid sodium hydroxide–chloroform mixtures containing 350 molecular weight α‐methyl‐ω‐hydroxy‐poly(oxy‐1,2‐ethanediyl) (Carbowax 350) as a phase transfer catalyst. This study describes the influence of reaction variables on rate and the partitioning of dichlorocarbene between dichlorocyclopropanation and hydrolysis. The results are consistent with a kinetic model derived for the case where mass transfer is not rate limiting. However, this does not apply at high conversions where mass transfer control occurs due to large increases in viscosity. Higher BR concentrations can be achieved by replacing chloroform with methylene chloride containing stoichiometric amounts of chloroform. This mass action effect causes more favorable partitioning toward cyclopropanation; otherwise, chloroform and methylene chloride behave similarly as solvents. Water is an essential component in this reaction because it greatly increases the ability of the catalyst to extract sodium hydroxide into the organic phase.