Infrared and nuclear magnetic resonance absorption and isomerism of 3-aminocrotonic esters. Part III

Abstract

The i.r. and ¹H n.m.r. spectra of 3-(dialkylamino)crotonates indicate that these substances exist as the isomer with the (E)-configuration; the i.r. spectra also show the presence of minute amounts of the sterically more hindered (Z)-form. The low temperature ¹H n.m.r. spectra reveal the existence of barriers to rotation around the C-N which amount to ca. 11–14 kcal mol^–1. Some complexities in the i.r. spectra suggest in addition the existence of smaller energy barriers to rotation around the C–CO₂R single bond.