A Theoretical Investigation on the Reaction Mechanism of the C₈H₁₀^+· Side‐Chain Decomposition Processes

Abstract

The dissociation of ethylbenzene cation C8H10+· served as a prototype to investigate the decompasition mechanisms of alkylbenzene cations. The reactions of C8H10+· decomposition reaction system have been studied extensively at the B3LYP/6‐311++G∗︁ ∗︁ level with Gaussion 98 package. The chain reaction of C8H10+· dissociation is initiated by C–H bond rupture. All reaction channels were fully investigated with the vibrational mode analysis to confirm the transition states and reveal the reaction mechanism. The energetically most favorable pathway is C8H10+·→TS4→P2+H· and the channel leading to C8H10+· and C2H4 is also competitive.

A Theoretical Investigation on the Reaction Mechanism of the C9H12+· Side‐chain Decomposition

“…The imaginary value (198i cm -1 , 10.4211 km•mol -1 ) was assigned to the stretch mode of the breaking C(12)-H (14) bond, which is extended to 0.2556 nm. From Figure 1 it can be seen that in TS4 a 6 7 Π delocalized bond is forming, and H (14) atom is almost perpendicular to this plane.…”

“…For TS3, considerable electrons concentrate on C (13) and C (16), so this C(13)-C(16) bond will be ruptured and C(13) and C(16) will capture an electron to leave; but C(3)-C(12) bond does not break like the C(12)-C(16) bond in TS1, for C(12) atom (-0.881e) is actually the negative charge center and it is the electrostatic attraction that makes C(12) still link to C(3) atom. As to TS4 and TS5, Table 2 shows that the leaving hydrogen atoms are attracting electrons and the total atomic charges of the leaving H (14) and H(18) are decreased to 0.078e and 0.074e, respectively.…”

“…Compared with the C 8 H 10 i ＋ decomposition system, 14 there is a direct decomposition pathway via TS3 in C 9 H 12…”

“…C 9 H 12 i ＋ is an ideal model compound for studying the complex decomposition processes of alkylbenzene cations, and a theoretical study on the reaction mechanism of this unique radical can help us to understand the decomposition processes. Recently, our team carried out a theoretical investigation on the reaction mechanisms of the alkylbenzene cation C 8 H 10 i ＋ , 14 and found that the thermal decomposition of aromatic heterocyclic radicals could be interpreted as a chain reaction initiated by C-H bond scission, so maybe the degradation processes of these activated phenylpropane cations also begin with the departure of hydrogen atoms. In this paper, we will carry out a theoretical investigation to elucidate the reaction mechanism for the C 9 H 12 i ＋ decomposition reaction system.…”