GAS-PHASE-LIKE BEHAVIOR IN SOLUTION CHEMISTRY

Using data from this work and from the literature, the standard free-energy changes for reactions i and ii, DELTA-G(H+)(g) and DELTA-G-degrees-I2(soln), are compared: B(g) + H+(g) reversible BH+(g) (i); B(soln) + I2(soln) reversible B...I2(soln) (ii). B's are S(sp3) and N(sp2 and sp3) n-donor bases (all compounds for which data sets are extensive and reliable), spanning a range of DELTA-G(H+)(g) of ca. 65 kcal.mol-1. Within families, DELTA-G(H+)(g) and DELTA-G-degrees-I2(soln) are linearly related. Thus, a pattern of reactivity similar to that prevailing in the gas phase can be found in acid-base reactions in solution, provided charge dispersal through hydrogen bonding to the solvent is minimized.