SOLVATOCHROMIC COMPARISON METHOD SERIES .13. LINEAR SOLVATION ENERGY RELATIONSHIPS .5. CORRELATIONS BETWEEN INFRARED DELTA-NU-VALUES AND THE BETA-SCALE OF HYDROGEN-BOND ACCEPTOR BASICITIES

Infrared Av values (free minus hydrogen bonded) of X-H bonds are shown to be linear with β values within families of hydrogen bond acceptor (HBA) bases having similar bonding sites, but not between families. Classes of HBA bases considered are (in order of increasing Δv's) double-bonded oxygen, single-bonded oxygen, pyridine bases, and trialkylamines. Reasons suggested for the nonlinearity of Δv with β between families involve differing geometries of the hydrogen bonds (angles between axis of vibrating X-H bond and direction of acceptor dipole) and differing hybridizations on the acceptor atoms. Linear relations between Δv and β within families are used to amend and expand the scale of HBA basicities. © 1979, American Chemical Society. All rights reserved.