Figure 13. Flexible scan of the C(8)–C(7)–O(14)–H(30)
dihedral.
Study of the gas-phase reaction mechanism.
The biggest difference between the gas- and liquid-phase reactions is
that there are solvent molecules in the latter. For the same reaction,
there are different reaction rates and likely different reaction
processes. This is because the dielectric constant, polarity, ionic
strength, and solvation have different effects on the reaction rate. For
the system we studied, the solvent molecules themselves are involved in
the reaction. Therefore, the reaction mechanism under the gas-phase
condition is discussed, and the similarities and differences from the
solution-phase condition were analyzed.
For elementary reactions 1–3, the gas-phase reaction follows the same
reaction paths as the liquid-phase reaction. Intermediates1a’ _gas, 2a’ _gas, med1_gas, and med2_gas, were
formed during the reaction, as well as transition states TS1_gas,
TS2_gas, and TS3_gas. The optimized structures of the stationary
points are basically similar, as shown in Figure 14.