The Dipole Moments of the Oligomer of Ethylenediamine

Abstract The dipole moments of ethylenediamine (N=1), diethylenetriamine (N=2), triethylenetetramine (N=3), and tetraethylenepentamine (N=4) were measured in a benzene solution at 25°C and 45°C. The observed dipole moments of N=1, N=2, N=3, and N=4 are 1.89 D, 2.22 D, 2.37 D, and 2.56 D respectively at 25°C, and 1.84 D, 2.22 D, 2.36 D, and 2.58 D respectively at 45°C. The dipole moments were theoretically calculated on the assumptions that; (i) the dipole moments of these chain molecules are given by the vector sum of the dipole moments of the polar groups of amine, and (ii) all internal rotations about single bonds are free. The calculated values of N=1, N=2, N=3, and N=4 are 1.84 D, 2.15 D, 2.43 D, and 2.68 D respectively. The agreement between the observed values and the calculated values is satisfactory. It may, therefore, be expected that the molecular chains will be in the random coil state. The intramolecular hydrogenbonding is very weak, as there is no temperature dependence of the observed dipole moments.