DIFFERENTIAL SCANNING CALORIMETRY STUDIES ON UREA - CARBOXYLIC-ACID INCLUSION COMPLEXES

Inclusion complexes of urea with several long chain fatty acids (of up to 30 C atoms) were prepared and their thermal behavior was investiga ted by differential scanning calorimetry (DSC). The host-guest ratios in these complexes were determined by titration against standard NaOH solution using pH to determine the end point. The DSC thermograms show ed that complexes of the higher saturated acids (with 23 or more C ato ms) rue stable even above the melting point of urea. This is contrary to the currently accepted view that for complexes of urea and fatty ac ids, the outer urea lattice simply melts when the melting point of ure a is reached, causing the complex to decompose.