Modeling Gas-Phase Unimolecular Dissociation for Bond Dissociation Energies: Comparison of Statistical Rate Models within RRKM Theory

The
Rice–Ramsperger–Kassel–Marcus (RRKM) theory
provides a simple yet powerful rate theory for calculating microcanonical
rate constants. In particular, it has found widespread use in combination
with gas-phase kinetic experiments of unimolecular dissociations to
extract experimental bond dissociation energies (BDEs). We have previously
found several discrepancies between the computed BDE values and the
respective experimental ones, obtained with our empirical rate model,
named L-CID. To investigate the reliability of our rate model, we
conducted a theoretical analysis and comparison of the performance
of conventional rate models and L-CID within the RRKM framework. Using
the previously published microcanonical rate data as well as reaction
cross-section data, we show that the BDE values obtained with the
L-CID model agree with the ones from the other rate models within
the expected uncertainty bounds. Based on this agreement, we discuss
the possible rationalization of the good performance of the L-CID
model.