Chain conformation of aliphatic α,ω-diamines in aqueous solutions

Potentiometric titration of aliphatic α,ω-diamines such as 1.3-, 1,4-, and 1,6-diamines was carried out in aqueous solutions with and without added salt to study the effect of electrostatic interactions on the chain conformations. The ratios of first to second association constants of proton K₁/K₂ were larger than 4 indicating the effects of electrostatic interactions on the second association constant in a similar manner as α,ω-diacids. These data were analyzed by the theories of Bjerrum and Kirkwood-Westheimer, and the resulting charge distances were compared with the end-to-end distances of various chain models.