Kinetics and mechanism of the aminolysis of O-ethyl S-aryl dithiocarbonates in acetonitrile

✍ Scribed by Hyuck Keun Oh; Jun Yong Lee; Jeong Hwan Yun; Young Sook Park; Ikchoon Lee

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 139 KB
• Volume: 30
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/(sici)1097-4601(1998)30:6<419::aid-kin4>3.0.co;2-v

✦ Synopsis

The aminolysis reactions of O-ethyl S-(Z-phenyl) dithiocarbonates ( H, Z ϭ p-CH , 3 p-Cl, and p-NO 2 ) with anilines (AN) and N,N-dimethylanilines (DMA) in acetonitrile at 30.0ЊC are investigated. Relatively small values of and for ␤ (␤ ,0.4 ca. 0.7) ␤ (␤ Ϫ0.1 ca. Ϫ0.4) X n u c Z l g both ANs and DMAs, significantly large values (1.1 ca. 1.9) involving deuterated anilines, k /k H D and large negative values for ANs (Ϫ0.56) are interpreted to indicate a concerted mech-XZ anism for both ANs and DMAs but with a hydrogen bonded four-center type transition state (TS) for ANs. The relative leaving ability, is smaller for ANs than k(Z ϭ p-NO )/k(Z ϭ p-CH ), 2 3

for DMAs, especially for a weaker nucleophile (1.9 and 4.7 for AN and DMA, respectively, with ). This suggests that the rate enhancement by the hydrogen-bond formation in the X ϭ p-Cl four-center type TS for AN is greater for a weaker nucleofuge especially when the (Z ϭ p-CH ), 3 nucleophile is weaker.