SUBSTITUENT EFFECTS IN THE GAS-PHASE THERMOLYSIS OF ARYL TERT-BUTYL ETHERS AND SULFIDES

The pyrolyses of p‐nitrophenyl t‐butyl ether, p‐methoxyphenyl t‐butyl ether, p‐aminophenyl t‐butyl ether, p‐nitrophenyl t‐butyl sulfide, and propargyl t‐butyl sulfide have been studied in a stirred‐flow reactor over the temperature range 430–530°C and pressures in the range 7–14 torr, using toluene as carrier gas. The reactions yielded between 90 and 99% isobutene plus the corresponding phenol, thiophenol, or thiol as products. The first order rate coefficients for reactant consumption, based on isobutene production, followed the Arrhenius equations p‐nitrophenyl t‐butyl ether (Formula Presented.) p‐methoxyphenyl t‐butyl ether (Formula Presented.) p‐aminophenyl t‐butyl ether: (Formula Presented.) p‐nitrophenyl t‐butyl sulfide (Formula Presented.) propargyl t‐‐butyl sulfide: (Formula Presented.) The results support a unimolecular elimination of the isobutene involving polar, four‐center cyclic transition states. Copyright © 1990 John Wiley & Sons, Inc.