In Situ Generation of Strong Bases from Alkaline and Alkaline–Earth Carbonates

Abstract

Strong bases from alkaline and alkaline-earth metal carbonates were generated in situ by adding a small amount of acetic acid at reflux in toluene under water-free conditions. Their basic strength reached superbasicity thus changing the color of 4-chloroaniline (H−=26.5). The high conversion of ethyl acetate in its self-condensation over decomposed carbonates, which require strong basicity to abstract protons from ethyl acetate (pKa=25), also confirmed the formation of strong bases. Adding acetic acid during the reaction indicated that metal oxides—decomposed materials from carbonates—were responsible for their high catalytic activity. The lack of sufficient coordination of in situ generated metal oxides was considered to be a plausible cause for their strong basicity.