A facile preparation and the crystal structures of N, N′‐dialkyl‐2,6‐ pyridinedimethanaminium halides were described. Direct substitution reactions were convenient to prepare specifically secondary diamines using 2,6‐bis(chloromethyl)‐ pyridine and 10 equivalents molar of primary alkylamines. Hydrogen halide salts were obtained in good yields and the crystal structures of three N, N′‐dialkyl‐2,6‐pyridinedimethanaminium salts were determined by the X‐ray diffraction method. A cancroid structure around the pyridine ring was observed commonly in the three salts. Acidity constants of the three salts were determined. Since the pKa values of the salts were slightly smaller than those of several common triamines previously reported, the acidities did not correlate with the cancroid structure directly. This is probably due to electrostatic interaction of the two protonated amino groups, furthermore the central pyridine nitrogen was not protonated in all the ligands.
