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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 35, Number 7
BKCSDE 35(7)
July 20, 2014 

Elimination Reactions of Aryl Furylacetates Promoted by R2NH-R2NH2+ in 70 mol% MeCN(aq). Effects of β–Aryl on the Ketene-Forming Transition-State
Sang Yong Pyun*, Ju Chang Kim, Bong Rae Cho*
Elimination, E2 and E1cb Mechanism, β–Aryl Group effect
Ketene-forming elimination from 2-X-4-nitrophenyl furylacetates (1a-d) promoted by R2NH-R2NH2 + in 70 mol % MeCN(aq) has been studied kinetically. When X = Cl and NO2, the reactions exhibited second-order kinetics as well as Brönsted β = 0.37-0.54 and |βlg| = 0.31-0.45. The Brönsted β decreased with a poorer leaving group and |βlg| increased with a weaker base. The results are consistent with an E2 mechanism. When the leaving group was changed to a poorer one [X= H (1a) and OCH3 (1b)], the reaction mechanism changed to the competing E2 and E1cb mechanisms. A further change to the E1cb mechanism was realized for the reaction of 1a with i-Pr2NH/i-Pr2NH2 + in 70 mol % MeCN-30 mol % D2O. By comparing the kinetic results in this study with the existing data for ArCH2C(O)OC6H3-2-X-4-NO2, the effect of the β-aryl group on the ketene-forming elimination was assessed.
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