MELTING BEHAVIOR OF A SERIES OF DIAMIDES

The melting behaviour of diamides of general formula (n - CpH2p+1)CONH-(CH2)qNHCO(n - CpH2p+1) has been investigated by calorimetric, dilatometric and IR techniques. The conformational contribution to the melting entropy, calculated from the hypothesis of complete conformational freedom of the molecules at the melting point, has been compared with the experimental data. The higher melting points of the diamides, as compared with those of the linear hydrocarbons having the same number of conformationally flexible chain bonds, are attributed to a reduction of conformational freedom of the chain segments in the liquid state (caused by the large fraction of hydrogen bonds maintained in the melt). © 1979.