Collective dynamical properties of molten salts: molecular dynamics calculations on sodium chloride

Absorbance measurements have shown that the ligand exchange which occurs when tetrakis (triphenyl phosphite)nickel(0) (NiP$_{4}$) is dissolved in styrene (St) is the result of a rate-determining dissociation of NiP$_{4}$ followed by rapid complexing of NiP$_{3}$ with the monomer to form NiP$_{4}$(St). The enthalpy and entropy of activation for the dissociation have been determined, and agree with those deduced for the reaction in methyl methacrylate. Standard enthalpy and entropy changes for the overall process have also been evaluated. NiP$_{3}$(St) reacts with carbon tetrachloride, yielding radicals which initiate polymerization of the styrene. Kinetic evidence indicates a two-stage process, producing successively Ni$^{\text{I}}$ and Ni$^{\text{II}}$ derivatives. The rate constants of these reactions have been deduced, that of the first stage $(k_{3})$ from direct observations on the reaction between NiP$_{3}$(St) and CCl$_{4}$ and that of the second $(k_{4})$ by computation from the conversion-time relation for the polymerization. At 25$^{\circ}$C, $k_{3}$ is almost an order of magnitude higher than the corresponding constant for methyl methacrylate, and the reaction has a higher activation energy and frequency factor. On the other hand, $k_{4}$ is relatively small. With carbon tetrabromide the rate of the second stage is much higher, and the two processes cannot be separated. The Ni-monomer bond is stronger with methyl methacrylate than with styrene; in the latter case the dissociation energy is probably less than 20% of that of the Ni-P bond broken on dissociation of NiP$_{4}$. The entropy decrease associated with the formation of the NiP$_{3}$- monomer species is greater with methyl methacrylate.