Mechanisms of condensation of biaryl hydrocarbons

Abstract

Results of kinetic studies of the condensed phase thermal reactions of the following biaryl hydrocarbons are reported; 1,l'-binaphthyl, 1,2'-binaphthyl, 1-phenylnaphthalene, and 9-phenylanthracene. Condensation generally occurred in parallel with both isomerization and dissociation and rates depended on concentrations of hydrogen donors. In order to simplify mechanisms, detailed studies used donors capable of providing just one H atom.These were xanthene, fluorene, and diphenylmethane. Condensation of 1,l'-binaphthyl in the presence of xanthene, the most effective donor, followed a second-order rate law (first order in both xanthene and binaphthyl concentration), k/M-' s-l = 106.9*0.6 exp(-36.0 f 2.0 kcal/RT) (360-560 "C). Fluorene was one-fifth as effective as xanthene while diphenylmethane was nearly inert. A mechanism is proposed in which the key intermediates in all reactions are radicals created by H-atom transfer to the biaryls. In the condensation of naphthyl-containing biaryls, it is suggested that reactions are initiated by H transfer to a position next to the condensation site. Details of the unimolecular steps leading to condensation and isomerization, however, remain unclear. Over the conditions studied, the reaction order with respect to donor varied between one and zero. It is proposed that this variability is a result of competition between two pathways for H transfer, one involving a simple, selective H transfer from the donor t o a biaryl molecule, the other involving a free H-atom intermediate.

A ReaxFF molecular dynamics (MD) simulation for the hydrogenation reaction with coal related model compounds

“…The model compounds, which can represent the structural features of coal molecules, are usually selected to study the hydrogenation reaction [1,2]. So far, there have been many reports on the hydrogenation reaction mechanism of coal [3][4][5].…”

Mitigating crosslinking reactions through preconversion strategies. Final report

“…We suggest that initially reactions are dominated by the H-abstraction, f3-scission Rice-Henfeld sequence that is known (19) to dominate long-chain alkylbenzene pyrolysis. This sequence results in the generation of alkyl fragments and terminal olefins, either connected to or free from the pyrene.…”

Theoretical Study on the Potential Energy Surface of Decarbonylation of the Acetaldehyde by Ni2+

“…2, the reaction starts with the association of Ni 2+ with acetaldehyde leading to encounter complex M1, which is the first step. M1 is the first the intermediates, the 1 M1and M2 are connected through the multicenter transition state (TS1), which is formed by the metal ion insertion into the C-C bond of acetaldehyde. A striking feature of the transition state is Ni 2+ binds concomitantly to the O, H and C atom, both the carbon atoms of the breaking C-C bond, and one of the H atoms of the migrating methyl group.…”

“…2+ center interacts with these atoms closely. Although the transition state TSl is the first saddle between the intermediate M1 and M2, the bond distance is closed to the M2, so it is the late transition state of potential energy surface, from the bond distance and the angle, it can be seen that TS1 has an overall Cs symmetry with the symmetry plane defined by 1 Ni- 4 O-2 C-5 C, This transition state is expected to be stabilized to some extent by an agnostic interaction between the 2C -H1 bond and the Ni 2+ center as evident by the stretched bond length of 2 C-5 C, As a consequence, it lies below the entrance channel by 11.2 kcal/mol, which translates into an energy barrier of 37.1 kcal/mol with respect to M1. Figure.2 the diagram of relative energies along the channels for the decarbonylation Transition state TS2 connects M2 and products, which was carefully confirmed by IRC calculations.…”

“…In this field, understanding the mechanisms of C-C and C-H activation of decarbonylation by transition metal ions are of particular interest. Researchers made a significant efforts the concerning these aspects [1][2][3][4][5][6][7] . Many experimental techniques have been used to study the mechanism of the bond activation of decarbonylation by transition metal ions.…”