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Gas‐phase thermolysis of N ‐methyl‐ N ‐phenyl‐ tert ‐butylsulfenamide and morpholinyl‐ tert ‐butylsulfenamide
Author(s) -
Martin Gonzalo,
Ascanio Julian,
Rodriguez Jesus
Publication year - 1998
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/(sici)1099-1395(199806)11:6<407::aid-poc5>3.0.co;2-g
Subject(s) - chemistry , toluene , thermal decomposition , arrhenius equation , yield (engineering) , gas phase , medicinal chemistry , decomposition , molecule , activation energy , stereochemistry , organic chemistry , thermodynamics , physics
N ‐Methyl‐ N ‐phenyl‐tert‐butylsulfenamide (MPSA) and morpholinyl‐tert‐butylsulfenamide (MOSA) were thermolyzed in a stirred‐flow reactor at temperatures of 340–390 °C and pressures of 7–13 Torr, using toluene as carrier gas, at residence times of 0.3–1.3 s. Isobutene was formed in 99% yield through first‐order reactions having the following Arrhenius parameters (A,s −1 , E a , kJ mol −1 ): MPSA, log A = 12.41 ± 0.02, E a = 158.8 ± 0.2; MOSA, log A = 12.91 ± 0.22, E a = 159 ± 3. It is proposed that the elimination of isobutene takes place by unimolecular reaction mechanisms involving polar, four‐center cyclic transition states, forming S ‐unsubstituted thiohydroxylamines as co‐products. Thermochemical parameters, estimated by semiempirical AM1 calculations, are reported for the latter and for the parent molecules. © 1998 John Wiley & Sons, Ltd.