A charge density analysis on the proximity effect in dicyanoalkanes

QTAIM atomic and bond properties of 21 linear alkyl dicyanoalkanes of formula NC(CH2)nCN (n = 0-20), and three larger molecules: C32H66, NC(CH2)30CH3, and NC(CH2)30CN, indicate that cyano groups can be considered statistically equivalent to those of a large cyanoalkane when they are separated by at least 14 methylene groups. When n < 19 there is at least one methylene group in the dicyanoalkane that differs significantly from those of NC(CH2)30CH3 or NC(CH2)30CN. Every cyano group produces an effect on the methylenes that is nearly independent of the position of the other one, hydrogens being more sensitive than carbons.