Is there a catalytic effect of HBr on the bromination of aromatics?

Recently, much attention has been paid to the theoretical study of the catalytic action of HCl in the chlorination of aromatics.
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What about the catalytic action of HBr in bromination reactions?

Experimental data

AV Shernyukov, AM Genaev, GE Salnikov, HS Rzepa, VG Shubin. Noncatalytic bromination of benzene: A combined computational and experimental study. J. Comput. Chem. 2016, 37 (2), 210-225. DOI: 10.1002/jcc.23985

C₆H₆ + Br₂ → C₆H₅Br + C₆H₄Br₂ + HBr
(0.032 ml of benzene, 0.37 ml of bromine, 0.11 ml of CD₂Cl₂ in sealed NMR tube at 0 °C)

¹H NMR (600 MHz) monitoring

According to these kinetic data, the hydrogen bromide formed during the reaction has no effect on the rate constant of benzene bromination. The catalytic effect of HBr is absent.

A Genaev, HS Rzepa, AV Shernyukov, G Salnikov, V Shubin. Elevated Reaction Order of 1,3,5-tri-tert-butylbenzene Bromination as Evidence of a Clustered Polybromide Transition State: a Combined Kinetic and Computational Study. Org. Biomol. Chem., 2019, 17, 3781-3789. DOI: 10.1039/C9OB00607A

Scheme of the reaction

Kinetics plot

It has been found that hydrogen bromide affects the rate of the bimolecular debromination reaction III+HBr→I+Br₂, but has no effect on the rate constants of the bromination reactions I→III and II→IV. There is no catalytic effect of HBr.

DFT calculations

Geometry optimization by DFT/PBE/Λ1 (PRIRODA program [Chem. Phys. Lett. 1997, 281, 151; Russ. Chem. Bull. 2005, 54, 820])
with thermochemical ΔG (298.15 K) and Grimme's D3(BJ) dispersion corrections [J.Chem. Phys. 2010, 132, 154104; J. Comp. Chem. 2011, 32, 1456] for the energy of optimized geometry

Basis Λ1 [Chem. Phys. Lett. 2005, 416, 116; Theor Chem Acc (2019) 138: 40]: H (6s,2p)→[2s,1p]; C (10s,7p,3d)→[3s,2p,1d]; Br (19s,15p,11d)→[5s,4p,2d]

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Calculations show that the addition of HBr to the PhH+Br₂ system leads to a significant decrease in the barrier of the bromination reaction. But if we involve in the consideration the trimolecular reaction PhH+Br₂+HBr, then we cannot ignore another trimolecular reaction, PhH+Br₂+Br₂. Under conditions of excess bromine, the statistical probability of the formation of a pre-reaction complex comprising two Br₂ molecules is higher than that of Br₂+HBr. And the reaction barrier is lower. Therefore, the catalytic effect of HBr should not manifest itself. As observed in the experiment.

03.07.2019