22719-89-7Relevant articles and documents
Kinetics and mechanism of the aminolysis of ethyl aryl carbonates in acetonitrile
Koh, Han Joong,Lee, Ji-Won,Lee, Hai Whang,Lee, Ikchoon
, p. 710 - 716 (2007/10/03)
The aminolysis reactions of ethyl aryl carbonates with benzylamines in acetonitrile at 25.0°C are investigated. The base-catalyzed path, k2, disappears when strong nucleophiles (X = p-CH3O and p-CH3) react with a substrate activated by a strong nucleofuge (Z = p-NO2). The large magnitude of ρ(x) (-1.7 to -2.5), ρ(z) (3.4 to 4.3), and ρ(xz) (1.4) values, and relatively large k(H)/k(D) (1.6 to 1.8) found for the uncatalyzed path (k1) can be accounted for in terms of a stepwise mechanism with rate-limiting expulsion of the phenoxide leaving group. The catalyzed process (k2) is characterized by the much smaller magnitude of ρ(x) (-1.0 to -1.7), ρ(z) (0.4 to 0.7), and ρ(xz) (0.2), the larger k(H)/k(D) (2.1 to 2.5) values, and the lower ΔH(+) values (1.8-1.9 kcal mol-1) than those of the uncatalyzed process (k1) with large negative ΔS(+) values (-65 to -67 cal K-1 mol- 1). These results are consistent with four- and six-centered transition states for the two processes, k1 and k2, respectively.
