INVESTIGADORES
GRANADOS Alejandro Manuel
artículos
Título:
Hydrolysis of Fischer Carbene Complexes. Steric Effects of the pi-donor group
Autor/es:
MARTIN E. ZOLOFF MICHOFF; RITA H. DE ROSSI; ALEJANDRO M. GRANADOS
Revista:
JOURNAL OF ORGANIC CHEMISTRY
Editorial:
American Chemical Society
Referencias:
Año: 2006 vol. 71 p. 2395 - 2401
ISSN:
0022-3263
Resumen:
Rate constants for the hydrolysis of Fischer carbenes (CO)5CrdC(OR)Ph (R ) n-propyl, neopentyl,
isopropyl, and menthyl) in 50% MeCN-50% water (v/v) at 25 °C are reported. The rate constants for
the addition of -OH to the carbene carbon are 5.3, 3.7, 0.84, and 0.01 M-1 s-1, respectively. These rate
constants give linear correlations with the corresponding rate constants for the hydrolysis of esters such
as acetate, benzoate, and formiate. The slopes of the plots of the observed rate constants for the carbenes
vs the rate constants for the esters are 1.4 and 1.2 for acetate and benzoate, respectively, indicating that
the factors that decrease the reactivity of the two types of compounds are similar, but the carbenes show
higher sensitivity. The rate constants are well correlated with several steric parameters giving a value of
-3.84 for the Chartons parameter. The results show that the steric bulkiness of the R group is the
main factor determining the reactivity differences for these carbene complexes.