Premium
Kinetics and mechanism of the aminolysis of thiophenyl methylacetates in acetonitrile
Author(s) -
Oh Hyuck Keun,
Yang Jin Hee,
Cho In Ho,
Lee Hai Whang,
Lee Ikchoon
Publication year - 2000
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/1097-4601(2000)32:8<485::aid-kin6>3.0.co;2-x
Subject(s) - aminolysis , chemistry , kinetic isotope effect , acetonitrile , cationic polymerization , deuterium , amine gas treating , reactivity (psychology) , medicinal chemistry , selectivity , kinetics , stereochemistry , organic chemistry , catalysis , physics , quantum mechanics , medicine , alternative medicine , pathology
The aminolysis of Z‐thiophenyl methylacetates (C 2 H 5 C(O)SC 6 H 4 Z) 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 β X (= 1.2 ∼ 2.5) and β z (= −0.9 ∼ −1.5), (ii) the normal kinetic isotope effects ( k H / k D ≅ 1.2) involving deuterated benzylamines (XC 6 H 4 CH 2 ND 2 ), (iii) a large positive ρ xz (= 2.4) and (iv) adherence to the reactivity‐selectivity principle in all cases. The extremely large β X (β nuc ) 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 pK a o (≥ 10.0) is high due to a large ratio of the expulsion rates of the amine ( k −a ) to thiophenolate ( k b ) ( k −a / k b ) from the T ± . © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 485–490, 2000