CESIUM ION-PAIR ACIDITIES OF SOME N,N-DIALKYLACETAMIDES AND AGGREGATION OF THEIR CESIUM ENOLATES IN TETRAHYDROFURAN

Cesium ion pair acidities are reported of some N,N-dialkylacetamides a t 25 degrees C in tetrahydrofuran. The cesium enolates of alpha-arylac etamides are essentially monomeric at concentrations of about 10(-4) N T, but small amounts of dimers are present for the enolates of N,N-dim ethyl- and N,N-diethyl(4-biphenylyl)acetamide (K-dimer is approximatel y 400 M(-1)). The cesium enolate of N,N-dimethyl-diphenylacetamide for ms small amounts of dimers, but the dimerization constant of <100 M(-1 ) is near the limit of detection of our methods. The enolate of N,N-di ethylacetamide has an average aggregation number of 3.3, consistent wi th a mixture of dimers and tetramers. The cesium ion pair pKs of the a lpha-arylacetamides are about 25-26, and that of N,N-diethylacetamide is greater than 33.7. The acidity data are in good agreement with meas urements that have been reported in the literature for similar systems .