Neighbouring group participation in the gas-phase pyrolysis kinetics of 4-(N-methyl-N-phenylamino)-1-butyl acetate and 4-(N-phenylamino)-1-butyl acetate

✍ Scribed by Gabriel Chuchani; Nouria Al-Awadi; Rosa M. Domínguez; Alexandra Rotinov; Armando Herize; Kamini Kaul

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 64 KB
• Volume: 13
• Category: Article
• ISSN: 0894-3230
• DOI: 10.1002/1099-1395(200005)13:5<266::aid-poc240>3.0.co;2-q

✦ Synopsis

The pyrolysis kinetics of two phenylaminobutyl acetates were determined in a static system over the temperature range 359.7-399.6 °C and the pressure range 23.8-95 Torr. The reactions, in vessels seasoned with allyl bromide and in the presence of the free radical inhibitor toluene, are homogeneous and unimolecular, and obey a firstorder rate law. The overall rate coefficients are expressed by the following equations: for 4-(N-methyl-Nphenylamino)-1-butyl acetate, log[k 1 (s À1 )] = (13.92 AE 0.36) À (210.4 AE 4.5) kJ mol À1 (2.303RT) À1 ; and for 4-(Nphenylamino)-1-butyl acetate, log[k 1 (s À1 )] = (12.03 AE 0.43) À (188.3 AE 5.3) kJ mol À1 (2.303RT) À1 . The decomposition of these substrates undergoes a parallel reaction. The predominant primary product, the corresponding heterocyclic product, appears to be the result of an anchimeric assistance of the amino substituent for a back-side displacement. This suggests that an incipient ion-pair type of mechanism may be operating during the process of elimination. The Arrhenius expressions for the parallel decomposition of each of the aminobutyl acetate substrates are presented and discussed.