A Kinetic Study on Michael-type Reactions of 1-(X-Substituted Phenyl)-2-propyn- 1-ones with Amines: Effect of Amine Nature on Reactivity and Mechanism

摘要: Second-order rate constants have been measured spectrophotometrically for the Michael-type reaction of 1-(Xsubstituted phenyl)-2-propyn-1-ones (2a-f) with amines in H2O at 25.0 ± 0.1 °C. A linear Bronsted-type plot is obtained β nuc = 0.25 0.02, a typical value reactions which proceed through stepwise mechanism attack amine on electrophilic center being rate-determining step. Secondary alicyclic are found to be more reactive than isobasic primary amines. The Hammett 2a-f morpholine not linear, i.e., substrate strong electron-donating group (e.g., 4-MeO) exhibits negative deviation from plot. However, Yukawa-Tsuno same an excellent correlation ρ 0.62 and r 0.82. Thus, it has proposed that nonlinear due change step but ground-state stabilization resonance interactions.