287471-39-0Relevant academic research and scientific papers
Kinetics and mechanism of the aminolysis of thiophenyl methylacetates in acetonitrile
Oh, Hyuck Keun,Yang, Jin Hee,Cho, In Ho,Lee, Hai Whang,Lee, Ikchoon
, p. 485 - 490 (2000)
The aminolysis of Z-thiophenyl methylacetates (C2H5C(double bond O)SC6H4Z) with X-benzylamines in acetonitrile has been investigated at 45 °C. The reaction is found to proceed by a stepwise mechanism in which the rate-determining step is the breakdown of the zwitterionic tetrahedral intermediate, T±, with possibly a hydrogen-bonded four-center-type transition state. These mechanistic conclusions are drawn based on (i) the large magnitude of βX (= 1.2 to approximately 2.5) and βz (= -0.9 to approximately -1.5), (ii) the normal kinetic isotope effects (kH/kD?1.2) involving deuterated benzylamines (XC6H4CH2ND2), (iii) a large positive ρxz (= 2.4) and (iv) adherence to the reactivity-selectivity principle in all cases. The extremely large βX (βnuc) values can be accounted for by the loss of a strong localized cationic charge on the N atom of benzylamines in the expulsion from the T±. The pKa° (≥10.0) is high due to a large ratio of the expulsion rates of the amine (k-a) to thiophenolate (kb) (k-a/kb) from the T±.
