Subcritical solvent effects on a parallel Diels-Alder reaction network

The effect of pressure on the measured bimolecular rate constants of a para llel Diels-Alder reaction network in subcritical propane at 80 degrees C is determined. The network consists of maleic anhydride reacting simultaneous ly with isoprene and 1,3-cyclohexadiene. A phase behavior observation is ma de for each reaction to ensure the homogeneity of the system. Ratios of the bimolecular rate constants measured simultaneously in the parallel reactio n network are compared to the ratios obtained when the two reactions are ca rried out independently. Also, a comparison of the experimental pressure ef fect for each independent reaction and the reaction network to predictions of the thermodynamic pressure effect using transition-state theory and the Peng-Robinson equation of state is made. Furthermore, an attempt is made to correlate the normalized rate constants of the individual reactions with t he density of the solution. The results of the investigations are interpret ed in the context of local reactant concentrations about the maleic anhydri de and solvent-solute/cosolvent-solute interactions.