249938-85-0Relevant articles and documents
A new, "elongated" oxo ketene intermediate in the dissociative hydrolysis of 2,4-dinitrophenyl (2E,4E)-5-(4′-hydroxyphenyl)pentadienoate
Cevasco, Giorgio,Vigo, Daniele,Thea, Sergio
, p. 1165 - 1167 (1999)
(matrix presented) Reactivity comparison, Arrhenius parameters, and trapping of the above-depicted unsaturated intermediate strongly suggest that the alkaline hydrolysis of the title ester follows a mechanism of the E1cB type. This is the first observation of the occurrence of a dissociative route in the hydrolysis of an acyl derivative with three π-systems interposed between the hydroxyl group (the internal nucleophile upon ionization) and the reaction center. Comparison with the hydrolysis of 2,4-dinitrophenyl 4′-hydroxybenzoate shows that interposition of the vinylenic groups is beneficial to the dissociative route.
Occurrence of an elongated p-oxo ketene intermediate in the dissociative alkaline hydrolysis of aryl (2E,4E)-5-(4'-hydroxyphenyl)pentadienoates
Cevasco,Vigo,Thea
, p. 7833 - 7838 (2007/10/03)
The alkaline hydrolysis of title esters possessing acidic leaving groups follows an E1cB mechanism involving the participation of an 'extra extended' p-oxo ketene intermediate. For the hydrolysis of the 2,4-dinitrophenyl ester kinetic data, activation parameters and trapping of the intermediate clearly indicate that the dissociative pathway carries the reaction flux. Break in the Bronsted plot of the apparent second-order rate constants versus the pK(a) of the leaving group suggests that the reaction mechanism changes from E1cB to B(Ac)2 for esters having pK(a) higher than about 6.
