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Superacids and Their Derivatives. III. Kinetics of the Oxonium Ion Formation from Superacid Esters and Tetrahydropyran. Oxonium-Ester Equilibria

1974; Oxford University Press; Volume: 47; Issue: 5 Linguagem: Inglês

10.1246/bcsj.47.1233

1348-0634

Shiro Kobayashi, Tadashi Ashida, Takeo Sàegusa,

Organic and Inorganic Chemical Reactions

Abstract Kinetic studies on the oxonium formation reaction between superacid esters (ROSO2X) and tetrahydropyran (THP) were carried out by means of NMR spectroscopy. The reaction was found to be an equilibrium process. (Remark: Graphics omitted.) The rate constant (k) of Sn2 reaction and the equilibrium constant (1⁄K=k⁄k′) were determined. The solvent effect was examined and k was found to be in the order: nitrobenzene>chlorobenzene≈CH2Cl2>liquid SO2. The effects of R and X in ROSO2X were studied. Relative reactivities of primary alkyl series in the reaction of ROSO2C1 with THP were: Me: Et: n-Pr=4.63: 1.0: 0.294 in CH2Cl2 and Me: Et: n-Pr=3.19: 1.0: 0.452 in nitrobenzene. The effect of X on k was in the order Cl≈CF3>F, the 1⁄K value being also extremely low when X=F. The result was discussed in relation to the kinetics of the polymerization of tetrahydrofuran (THF) by ROSO2X.