Reaction of 1,1-diphenylpropene with stannic chloride and hydrogen chloride

Abstract

SnCl4 and HCl have been found to react with 1,1-diphenylpropene to form a small equilibrium amount of the diphenylethylcarbenium ion. No further reaction is detectable, and the equilibrium between the three reactants may be determined from the uv absorption of the ion. The electrical conductances of the solutions have also been measured. The results are consistent with the formation of the salt of this carbenium ion with the SnCl5− anion. The salt in the concentrations formed in these experiments (ca. 10−5–10−4 M) was nearly all dissociated into free ions in methylene chloride solution. The equilibrium constant for formation of the salt was 2.0 M−2 at −30 °C, and the dissociation constant into ions 4.4 × 10−4 M. The overall heat of reaction to the carbenium ion salt was 8.8 kcal, most of which is attributed to the initial formation of the undissociated salt.