Kinetic studies of Lewis acidity. Part 2. Catalysis by tin(IV) chloride, by some organotin(IV) chlorides, and by tin(II) chloride of the anionotropic rearrangement of 1-phenylprop-2-en-1-ol in tetramethylene sulphone solution

Abstract

The kinetics have been measured for the rearrangement of 1-phenylprop-2-en-1-ol (1) to 3-phenylprop-2-en-1-ol (2) in tetramethylene sulphone solution, catalysed by various tin(IV) chloride species. The rate coefficients, k_n′ at 313.2 K, per unit concentration of the catalyst, were: SnCl₄, 305; PhSnCl₃, 86.4; p-MeC₆H₄SnCl₃, 18.7; MeSnCl₃, 6.60; PrⁿSnCl₃, 5.36; EtSnCl₃, 4.69; BuⁿSnCl₃, 1.62; (p-CIC₆H₄)₂SnCl₂, ca. 3 × 10^–2; Ph₂SnCl₂, 5.1 × 10^–3; Et₂SnCl₂, 1.4 × 10^–3, Me₂SnCl₂, 4.3 × 10^–4 dm³ mol^–1 s^–1. The reaction catalysed by SnCl₄ was studied with a range of added compounds, viz. H₂O, LiCl, LiCIO₄, and 1,8-bis(dimethylamino)naphthalene. Evidence was obtained for the involvement of both anhydrous SnCl₄ and its monohydrate as catalysts for the rearrangement. Tin(II) chloride has been found to be an effective catalyst for the rearrangement, with k_n(313.2 K)= 3.51 dm³ mol^–1 s^–1. Addition of phosphoryl chloride to SnCl₂ causes a sharp increase in rate, with a maximum corresponding to the species SnCl₂·POCl₃. The value of k_n(303.5 K)≃ 1 200 dm³ mol^–1 s^–1 makes this catalyst the most powerful yet found for the rearrangement.