Melting behaviour of a series of monoamides

The melting behaviour of the monoamides of general formula (n-C_pH_2p+1)CONH-(n-C_qH_2p+1) is investigated by differential scanning calorimetry (DSC) and infrared spectroscopy. The lower values of melting entropies, compared to those for linear hydrocarbons with the same number of conformationally flexible chain bonds, is attributed to a reduction in the number of conformations available to the hydrocarbon portion of the molecule, because of the large amount of hydrogen bonding maintained in the melt. The melting behaviour of the monoamides is compared with that of the diamides discussed in a previous paper 1]. The persistence of a network of hydrogen bonds in the melt of the diamides reduces the conformational freedom of the chain segments more than for the monoamides.