QUANTITATIVE SEPARATION OF ELECTRONIC AND STERIC SUBSTITUENT EFFECTS IN REACTIONS BETWEEN ALIPHATIC-AMINES AND ELECTRON-ACCEPTORS

The effects of three N substituents on reactivities of aliphatic amines were analyzed by means of freeenergy-related substituent constants and regression analysis. In hydrogen-bond formation with CHCl3 and charge-transfer-complex formation with I2, electronic and steric effects of three N substituents were quantitatively separated by means of the equation log K=ρ*Σρ*+alEsc(R1)+a2Esc(R2)+a3Esc(R3)+c, where K is the equilibrium constant, ρ*, a1, a2, and a3 are susceptibility constants, and c is the intercept. Σσ* is the sum of the Taft σ* values of three N substituents. Esc(R1), Ecs(R2), and Ecs(R3) are, respectively, the Hancock corrected steric constants of N-substituents R1, R2, and R3, where Esc(R1) > Eac(R2) > Esc(R3). Examination of literature data seems to suggest a general applicability of the present procedure to various reactivities of aliphatic amines. © 1979, American Chemical Society. All rights reserved.