ENTROPY EFFECT OF CHELATION

A detailed analysis of the entropy change of chelation of a typical reaction [M(NH2CH3)2n(H2O)N-2n]m+(aq)+nen(aq)=[M(en)n(H2 O)N-2n]m+(aq)+2nNH2CH3(aq) reveals five entropy factors as significant. The magnitudes of these factors have been evaluated by statistical mechanical methods. Combining these contributions yields the entropy change of chelation which agrees satisfactorily with the experimental values. In general, the entropy effect of chelation in the gas phase can be described as a combined effect of the three positive contributions ΔStran8ktion, ΔSintrinsic rotation, and ΔSsymmetry and isomer and a negative contribution, ΔSin,ernal rotation The entropy change of chelation in aqueous solution will differ significantly from that in the gas phase or in organic solvents. © 1979, American Chemical Society. All rights reserved.