Gas-phase thermolysis of allyl propargyl amine,allyl cyanomethyl propargyl amine,allyl propargyl 2-thiapropyl amine,and allyl methanesulfonyl propargyl amine

The title amines have been pyrolyzed in a stirred-flow reactor, at temperatures of 360–500°C, pressures of 7–16 torr, and residence times of 0.5–2.9 s, using toluene as carrier gas. The reaction products were allene, propene, and the corresponding imines. The ratio allene:propene varied in the range 6.7–1.6. The amines with CH₂CN and SO₂CH₃ substituents also formed HCN and SO₂. These appear to arise from complex free radical decomposition of the imine product. The first-order rate coefficients for the production of allene plus propene followed the Arrhenius equations: Allyl propargl amine: Allyl cyanomethyl propargyl amine: Allyl propargyl 2-thiapropyl amine: Allyl methanesulfonyl propargyl amine: Nonconcerted mechanisms, involving polar six center cyclic transition states, are suggested for the elimination of allene and propene. © 1994 John Wiley & Sons, Inc.