Lithium Salt Effect on the Ring-Opening Reactions of Propylene Oxide with Dichloroacetic Acid

Abstract

The reaction of propylene oxide (PO) with dichloroacetic acid (DCA) in the presence of lithium dichloroacetate was studied kinetically in ethereal solvents, dioxane and diglyme. The ring-opening of PO obeyecl the following kinetics,
ν=k3(a-x)²(b-x)+k2(a-x)(b-x)
k2=k′3C0
where a-x, b-x, and C0 are the concentration of DCA, PO, and lithium dichloroacetate, respectively. The reaction was accelerated to a considerable extent by the addition of lithium dichloroacetate. The linear relationship between k2 and C0 was not observed, and the higher the common salt concentration, the less the extent of acceleration of the reaction, which is presumably due to the association of the lithium salt. Then the rate constant k′3 was estimated from the slope of the above curve at C0=0. The acceleration of the reaction could be accounted for by the activation entropy rather than the activation enthalpy.