MONOMER SHIFT, DIMER SHIFT AND DIMERIZATION CONSTANT FOR SELF-ASSOCIATION DETERMINED GRAPHICALLY FROM THE NMR DILUTION SHIFT - PYRROLIDONE IN CDCL3 AS AN EXAMPLE

We describe a graphical method for analysis of dilution NMR shift data , which permits the self-consistent determination of the monomer shift , dimer shift, and dimerization constant for systems involving a monom er-dimer equilibrium. The new method specifically avoids the manual ex trapolation to zero concentration conventionally used to obtain the mo nomer shift. In addition, it provides quantitative measures for both t he consistency and error of the determination. Measurements of the dil ution shift for pyrrolidone in CDCl3 over a series of temperatures are used to demonstrate the applicability of the graphical method. The en thalpy and entropy of the dimerization reaction are determined via a v an't Hoff plot of the temperature dependence of the dimerization const ant.