A comparison of the urea inclusion compound forming ability of butanedioic, butenedioic and butynedioic acids esters

Abstract

The ease of formation of urea inclusion compounds of the dialkyl esters of succinic, fumaric, maleic and acetylenedicarboxylic acids has been determined using the size of the smallest chain length including all the chain atoms except the terminal hydrogens, which in the diester proved capable of forming a urea complex. The shorter the chain length required, the greater the ease of complex formation. The following are the shortest diesters forming a complex (in parenthesis the cross-sectional diameter which determines the chain length required): diethyl succinate (5 · 0 Å), diethyl fumarate (5·1 Å), di-n-propyl acetylenedicarboxylate (5·2 Å) and di-n-butyl maleate (5·3 Å). The formation of urea inclusion compounds was established by X-ray powder diffraction patterns.