THE PROTON BOUND ASSOCIATION OF LARGE MULTIFUNCTIONAL GROUP MOLECULES - TARTARIC ACID-ESTERS

The kinetics of production of proton-bound dimers of dimethyl- and diisopropyl-tartrate were analyzed by the method of initial slopes. From the pressure dependence of the apparent bimolecular rate constant, the back-dissociation rate and radiative stabilization of the intermediate excited collision complex was calculated. The back-dissociation (10.3 and 2.8 x 10(3) s-1) and radiative (8.2 and 7.1 s-1) rates are compared to literature values for functionally similar acetone. In contrast to acetone these dimers exhibit a back-dissociation reaction to regenerate the monomer species. These results can be taken to imply a lower binding energy in these dimers due to steric effects. Competing reactions to form ions of m/z 145 and 235 were also observed for the dimethyl and diisopropyl ester, respectively.