160. The kinetics of aromatic halogen substitution. Part IX. Relative reactivities of monosubstituted benzenes

Robertson, P. W.; Mare, P. B. D. de la; Swedlund, B. E.

doi:10.1039/jr9530000782

Cited by 30 publications

(13 citation statements)

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“…Since N -CH 3 -BA decay occurred in both cases, albeit to different extents, these results confirmed that such brominating agents could degrade this compound even when the amide N-H functional group was not present. These brominating agents were expected to directly brominate the ring at the ortho - and para -positions . Although these byproducts were not directly measured, their formation was observed in a previous study when N -CH 3 -BA was exposed to Br 2 .…”

Section: Resultsmentioning

confidence: 93%

“…These brominating agents were expected to directly brominate the ring at the ortho-and para-positions. 54 Although these byproducts were not directly measured, their formation was observed in a previous study when N-CH 3 -BA was exposed to Br 2 . 54 Again, this evidence strongly implies that the Orton rearrangement pathway is not required for ring bromination to occur.…”

Section: ■ Materials and Methodsmentioning

confidence: 93%

“…Second, the decay of N-CH 3 -BA was slower than that of BA under both these experimental conditions, as previously observed when these two model compounds were exposed to free chlorine, 20 Cl 2 , 20,34 and when acetanilide and N-CH 3 -acetanilide were exposed to Br 2 . 54 One of these studies included our own prior study where this reduced reactivity of N-CH 3 -BA compared to BA was hypothesized to be driven by the steric inhibition of resonance. 20,34,54 Since both BA and N-CH 3 -BA were solely brominated at the ring and no other reactive sites or pathways were involved (see discussions above), a similar phenomenon is assumed here for the reduced reactivity of N-CH 3 -BA as compared to BA during bromination (Figure 3).…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

“…54 One of these studies included our own prior study where this reduced reactivity of N-CH 3 -BA compared to BA was hypothesized to be driven by the steric inhibition of resonance. 20,34,54 Since both BA and N-CH 3 -BA were solely brominated at the ring and no other reactive sites or pathways were involved (see discussions above), a similar phenomenon is assumed here for the reduced reactivity of N-CH 3 -BA as compared to BA during bromination (Figure 3).…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

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Reactivity of the Polyamide Membrane Monomer with Free Chlorine: Role of Bromide

Huang

Reber

Toomey

et al. 2021

Environ. Sci. Technol.

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Aromatic polyamide-based membranes are widely used for reverse osmosis (RO) and nanofiltration (NF) treatment but degrade when exposed to free chlorine (HOCl/OCl–). The reaction mechanisms with free chlorine were previously explored, but less is known about the role of bromide (Br–) in these processes. Br– may impact these reactions by reacting with HOCl to form HOBr, which then triggers other brominating agents (Br2O, Br2, BrOCl, and BrCl) to form. This study examined the reactivities of these brominating agents with a polyamide monomer model compound, benzanilide (BA), and a modified version of it, N-CH3-BA. The results indicated that all these brominating agents only attacked the aromatic ring adjacent to the amide N, rather than the amide N, different from the previously examined chlorinating agents (HOCl, OCl–, and Cl2) that attacked both sites. Orton rearrangement was not observed. Species-specific rate constants (k i , M–1 s–1) between BA and HOBr, Br2O, Br2, BrOCl, and BrCl were determined to be (5.3 ± 1.2) × 10–2, (1.2 ± 0.4) × 101, (3.7 ± 0.2) × 102, (2.2 ± 0.6) × 104, and (6.6 ± 0.9) × 104 M–1 s–1, respectively, such that k BrCl > k BrOCl > k Br2 > k Br2O > k HOBr. N-CH3-BA exhibited lower reactivity than BA. Model predictions of BA loss during chlorination with varied Br– and/or Cl– concentrations were established. These findings will ultimately enable membrane degradation and performance loss following chlorination in mixed halide solutions to be better predicted during pilot- and full-scale NF and RO treatment.

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Section: Resultsmentioning

confidence: 93%

Section: ■ Materials and Methodsmentioning

confidence: 93%

Section: ■ Materials and Methodsmentioning

confidence: 99%

Section: ■ Materials and Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Reactivity of the Polyamide Membrane Monomer with Free Chlorine: Role of Bromide

Huang

Reber

Toomey

et al. 2021

Environ. Sci. Technol.

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“…Second, it is also unclear whether Nchlorination is ever required for ring chlorination to occur. 8,9,20,21 Several studies found that the ring could be directly chlorinated or brominated by HOCl, Cl 2 , or Br 2 when the amide hydrogen was replaced by methyl, ethyl, or phenyl moieties within various polyamide-based compounds, 8,20,21 while another study did not observe a reaction. 9 Interestingly, further uncertainty regarding this mechanism arises from Orton and colleagues' own work published in the early 1900s.…”

Section: ■ Introductionmentioning

confidence: 99%

Reactivity of the Polyamide Membrane Monomer with Free Chlorine: Reaction Kinetics, Mechanisms, and the Role of Chloride

Huang

Reber

Toomey

et al. 2019

Environ. Sci. Technol.

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Aromatic polyamide thin-film composite membranes are widely used in reverse osmosis (RO) and nanofiltration (NF) due to their high water permeability and selectivity. However, these membranes undergo biofouling and can degrade and eventually fail during free chlorine exposure. To better understand this effect, the reactivity of the polyamide monomer (benzanilide (BA)) with free chlorine was tested under varying pH and chloride (Cl − ) conditions. The kinetic results indicated that the current existing mechanisms, especially the Orton rearrangement, were invalid. Revised reaction pathways were proposed where BA chlorination was driven by two independent pathways involving the anilide ring and amide nitrogen moieties. The ability for one moiety to be chosen over the other was highly dependent on the pH, Cl − concentration, and the resulting chlorinating agents (e.g., Cl 2 , HOCl, OCl − , and Cl 2 O) generated. Species-specific rate constants for BA with Cl 2 , OCl − , and HOCl equaled (7.6 ± 0.19) × 10 1 , (1.7 ± 1.5) × 10 1 , (2.1 ± 0.71) × 10 −2 M −1 s −1 , respectively. A similar value for Cl 2 O could not be accurately estimated under the tested conditions. The behavior of these chlorinating agents differed for each reactive site such that OCl − > HOCl for N-chlorination and Cl 2 > HOCl > OCl − for anilide ring chlorination. Experiments with modified monomers indicated that substituent placement largely affected which reactive site was kinetically favorable. Overall, such findings provide a predictive model of how the polyamide monomer degrades during chlorine exposure and guidance on how chlorine-resistant polyamide membranes should be designed.

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Directing and activating effects

Happer

Vaughan

1975

PATAI'S Chemistry of Functional Groups

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160. The kinetics of aromatic halogen substitution. Part IX. Relative reactivities of monosubstituted benzenes

Cited by 30 publications

References 0 publications

Reactivity of the Polyamide Membrane Monomer with Free Chlorine: Role of Bromide

Reactivity of the Polyamide Membrane Monomer with Free Chlorine: Role of Bromide

Reactivity of the Polyamide Membrane Monomer with Free Chlorine: Reaction Kinetics, Mechanisms, and the Role of Chloride

Directing and activating effects

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