Kinetics and mechanism of the aminolysis of aryl propanedithioates in acetonitrile

Citation
Hk. Oh et al., Kinetics and mechanism of the aminolysis of aryl propanedithioates in acetonitrile, NEW J CHEM, 25(2), 2001, pp. 313-317
Citations number
34
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Chemistry
Journal title
NEW JOURNAL OF CHEMISTRY
ISSN journal
1144-0546 → ACNP
Volume
25
Issue
2
Year of publication
2001
Pages
313 - 317
Database
ISI
SICI code
1144-0546(2001)25:2<313:KAMOTA>2.0.ZU;2-E
Abstract
The kinetics and mechanism of the aminolysis of aryl proanedithioates with benzylamines are investigated in acetonitrile at -35.0 degreesC. A large ma gnitude of the Hammett (rho (X) and rho (Z)) and Bronsted (beta (X) and bet a (Z)) coefficients and exceptionally large cross-interaction constant rho (XZ)(=3.5) are consistent with a stepwise mechanism in which leaving group expulsion from an intermediate, T+/-, is the rate-determining step. The fas ter rates observed for dithio esters (II) than for thio esters (I), and the validity of the reactivity-selectivity principle (RSP) are also in line wi th the mechanism proposed. The k(H)/k(D) values (=1.0-1.8) determined with deuterated benzylamines (XC6H4CH2ND2) and the activation parameters, DeltaH (similar or equal to8 kcal mol(-1)) and DeltaS(not equal)(=-16 to -23 e.u.) , suggest that proton transfer occurs concurrently with leaving group depar ture in the transition state.