Production mechanism of active species on the oxidative bromination following perhydrolase activity

Abstract

Hypobromous acid and molecular bromine have been described as the active species involved in the oxidative bromination using perhydrolase, which catalyzes the reaction from acetic acid and hydrogen peroxide to peracetic acid (AcOOH). However, the brominating activity of them in a chemical model system was lower than that of the active species produced by the spontaneous reaction between AcOOH and Br À . Consequently, acetyl hypobromite (AcOBr) was suggested as new active species on the bromination by detection of the decarboxylation in the reaction between AcOOH and Br À and the strong brominating power with some tolerance against H 2 O 2 . Its production mechanism was explained as the ionic reaction involving the protonated intermediate of AcOOH by kinetic analysis.

Revealing the nature of covalently tethered distonic radical anions in the generation of heteroatom-centered radicals: evidence for the polarity-matching PCET pathway

“…3a) and did not show the broad features between 400 and 500 nm, which completely excluded the initial formation of Br 2 (l max = 415 nm) (Section S5.3 †). 36 The clearly decreased absorption intensity and slight blue-shi were observed in the UV-vis spectrum when the PPO/TBAB system was illuminated for 60 min, thus revealing again that the key active species was unstable and photosensitive (Fig. S25 †).…”

Bromide Oxidation: A Safe Strategy for Electrophilic Brominations

“…[28a,42] However, some research suggests that this formation of peracetic acid can lead to the subsequent formation of AcOBr, a more potent brominating agent. [43] Solid 4Na 2 SO 4 • 2H 2 O 2 • NaCl crystals can also be used to produce peracetic acid, which can then be used for oxidative bromination or immediately as an oxidant. [23] Caution has to be taken with peracetic acid, since it can also epoxidise a double bond rather than brominating it.…”

“…This will then in turn oxidise the bromide in a reaction similar to Equation (9) [28a,42] . However, some research suggests that this formation of peracetic acid can lead to the subsequent formation of AcOBr, a more potent brominating agent [43] . Solid 4Na 2 SO 4 ⋅ 2H 2 O 2 ⋅ NaCl crystals can also be used to produce peracetic acid, which can then be used for oxidative bromination or immediately as an oxidant [23] .…”

Halogens in Seaweeds: Biological and Environmental Significance

“…When the structure of a related bromoperoxidase from Streptomyces aureofaciens was elucidated, it was found to contain a catalytic triad with a nucleophilic serine residue, like the hydrolases to which it is related [87]. For haloperoxidation, a carboxylic acid is needed, that is proposed to react with the serine to form an ester, which is attacked by H 2 O 2 to form a peracid, so that the enzyme could also be called a perhydrolase [88]; the peracid reacts with the halide to produce the halogenating intermediate, which is not known with certainty, but must be electrophilic. The perhydrolase activity is considered by some to be a side activity of hydrolases, such as lipases and esterases [89].…”