Effects of the Substituents on the Energy Flow of Toluene Derivatives in Collisions with N₂ and O₂

Abstract

The effects of the substituents in the energy flow in four toluene derivatives (o-chloro-, o,-bromo-, α-chloro-, and α-bromotoluene) on collision with N 2 and O 2 were investigated by classical trajectory methods. The energy loss by the α-derivatives of toluene is significantly higher than that of the o-derivatives. Furthermore, the substituent, Cl or Br, does not affect the energy loss. The dominant pathways for the vibrational decay of the excited o-derivatives are the vibration-translation (V-T) and vibrationvibration (V-V) energy transfers to N 2 /O 2 . In contrast, the vibrational relaxation of the excited α-derivatives occurs mainly through the V-T energy transfer. The efficiency of the intermolecular V-V energy transfer of the o-derivatives is significantly higher than that of the α-derivatives. In the o-derivatives, as the excited energy (E T ) increases, the excited C-H m bond frequency decreases; thus, the energy transfer via the V-V pathway increases. In the α-derivatives, the V-V energy transfer is not efficient for both N 2 and O 2 , although the C-H r and N 2 /O 2 vibrations are near resonance.

Isotope Effects on the Energy Flow and Bond Dissociations of Excited α‐Chlorotoluene in Collisions with H2/D2

“…The results reveal that the vibrational decay of α‐CT by H 2 are much greater than that of toluene by H 2 over the entire E T range. This enhancement in the vibrational relaxation of α‐CT compared to that of toluene has also been reported in α‐CT + N 2 /O 2 collision systems by Lee et al 27 . Furthermore, the energy loss of α‐CT in the α‐CT + H 2 collision system is also greater than that in the o ‐CT + H 2 collision system 33 .…”

“…Figure 2(b) presents the sum of the three pathways compared to the experimental values of a toluene + H 2 collision system reported by Toselli et al 12 The results reveal that the vibrational decay of α-CT by H 2 are much greater than that of toluene by H 2 over the entire E T range. This enhancement in the vibrational relaxation of α-CT compared to that of toluene has also been reported in α-CT + N 2 /O 2 collision systems by Lee et al 27 Furthermore, the energy loss of α-CT in the α-CT + H 2 collision system is also greater than that in the o-CT + H 2 collision system. 33 Moreover, the computed vibrational decay of α-CT is found to increase gradually with increasing E T .…”

“…The total energy loss of α-CT via D 2 collisions is seen to overtake that of the α-CT via H 2 collisions, when E T is greater than 30 000 cm −1 . It is interesting to note that the vibrational decay of α-CT in the α-CT + N 2 /O 2 collision systems 27 is much greater than that in the α-CT + D 2 system shown in Figure 3(a). When E T is 30 000 cm −1 , the vibrational decays of α-CT in the α-CT + N 2 and α-CT + O 2 collision systems are 483 and 527 cm −1 , respectively, compared to 282 cm −1 in the α-CT + D 2 system.…”

“…The potentials and spectroscopic constants of α-CT are obtained from Ref. 27. In the term representing London interactions, I i is the ionization potential and α i (i = 1, 2) is the polarizability of α-CT and H 2 , respectively; these are listed in Table 1.…”