The Acid Ionization Constant of HOCl from 5 to 35°

Morris, J. Carrell

doi:10.1021/j100884a007

Cited by 883 publications

(489 citation statements)

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“…Chlorine exhibits a pH and temperature dependent-equilibrium between the hypochlorous acid (HOCl) and the hypochlorite ion (OCl -), with the sum of the two commonly known as free chlorine (White, 1992). At 25°C and pH = 7.54 both species are found in equal concentrations (pKa 25°C = 7.537; (Morris, 1966)), but the concentration of HOCl is reduced to 35.3% of the added chlorine at pH 25°C =7.8 and to17.8% at pH 25°C =8.2. HOCl is the main active specie responsible for the disinfection effect of chlorine.…”

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confidence: 98%

Effect of pH on the formation of disinfection byproducts in swimming pool water – Is less THM better?

et al. 2012

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This study investigated the formation and predicted toxicity of different groups of disinfection byproducts (DBPs) from human exudates in relation to chlorination of pool water at different pH values. Specifically, the formation of the DBP groups trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs) and trichloramine (NCl 3 ), resulting from the chlorination of body fluid analog, were investigated at 6.0 ≤ pH ≤ 8.0. Either the initial concentration of active chorine or free chlorine was kept constant in the tested pH range. THM formation was reduced by decreasing pH but HAN, and NCl 3 formation increased at decreasing pH whereas the formation of HAAs remained constant. Under our experimental conditions, the formation of NCl 3 (suspected asthma inducing compound) at pH = 6.0 was an order of magnitude higher than at pH = 7.5. Furthermore, the effect of the presence of bromide on DBP formation was investigated and found to follow the same pH dependency as without bromide present, with the overall DBP formation increasing, except for HAAs. Estimation of genotoxicity and cytotoxicity of the chlorinated human exudates showed that among the quantified DBP groups, HAN formation were responsible for the majority of the toxicity from the measured DBPs in both absence and presence of bromide.

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confidence: 98%

Effect of pH on the formation of disinfection byproducts in swimming pool water – Is less THM better?

et al. 2012

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“…Solutions were prepared in chelex-treated buffers of 0.1 M phosphate (pH 6.5 to 8.5) allowing sufficient time to fully hydrate the glycosaminoglycans. Hypochlorous acid (Sigma) solutions were prepared freshly and the concentrations of stock solutions determined using the extinction coefficient of the hypochlorite ion of 350 M -1 cm -1 at pH values 10 or above [25].…”

Section: Methodsmentioning

confidence: 99%

“…HOCl has a pKa value of 7.59 [23,25] and therefore at physiological pH there is approximately a 50:50 mixture of the acid and its anion OCl -. In principle therefore, both species can participate in the substitution reaction to form chloramides.…”

Section: Introductionmentioning

confidence: 99%

Chlorination and oxidation of heparin and hyaluronan by hypochlorous acid and hypochlorite anions: effect of sulfate groups on reaction pathways and kinetics

Akeel

Sibanda

Martin

et al. 2013

Free Radical Biology and Medicine

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Hypochlorous acid (HOCl), produced in inflammatory conditions by the enzyme myeloperoxidase, and its anion, perchlorite ( OCl -) exist in vivo at almost equal concentrations. Their reactions with hyluronan and heparin (as a model for sulphated glycosaminoglycans in the extracellular matrix), have been studied as a function of pH. The major product in these reactions is the chloramide derivative of the glycosaminoglycans. Spectral, chloramide yield and kinetic measurements show sharply contrasting behaviour of heparin and hyaluronan and the data allow the calculation of second-order rate constants for the reactions of both HOCl and OCl -for all reaction pathways leading to the formation of chloramides and also oxidation products . By comparison with hyaluronan, it can be demonstrated that both N-sulphate and O-sulphate groups in heparin influence the proportions of these pathways in this glycosaminoglycan. Evidence is also given for further oxidation pathways involving a reaction of HOCl with the chloramide product of hyaluronan but not with heparin. The significance of these results for mechanisms of inflammation, particularly for fragmentation of extracellular matrix glycosaminoglycans is discussed.

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“…2 shows the experimental k values in correspondence to different pH conditions. This pH-dependent variation was ascribed to the speciation of both DPD and FC on the basis of their dissociation constants (pK DPD,1 ¼ 2.95, pK DPD,2 ¼ 8.46; pK HOCl ¼ 7.54, 25 C) (Morris, 1966;Moore et al, 1984). The kinetic model could be simplified based on the following facts:…”

Section: Determination Of Chlorination Rate Constants Of Dpd By Sfs Tmentioning

confidence: 99%

Determination of rapid chlorination rate constants by a stopped-flow spectrophotometric competition kinetics method

et al. 2014

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a b s t r a c tFree chlorine is extensively used for water and wastewater disinfection nowadays. However, it still remains a big challenge to determine the rate constants of rapid chlorination reactions although competition kinetics and stopped-flow spectrophotometric (SFS) methods have been employed individually to investigate fast reaction kinetics. In this work, we proposed an SFS competition kinetics method to determine the rapid chlorination rate constants by using a common colorimetric reagent, N,N-diethyl-p-phenylenediamine (DPD), as a reference probe. A kinetic equation was first derived to estimate the reaction rate constant of DPD towards chlorine under a given pH and temperature condition. Then, on that basis, an SFS competition kinetics method was proposed to determine directly the chlorination rate constants of several representative compounds including tetracycline, ammonia, and four a-amino acids. Although Cl 2 O is more reactive than HOCl, its contribution to the overall chlorination kinetics of the test compounds could be neglected in this study. Finally, the developed method was validated through comparing the experimentally measured chlorination rate constants of the selected compounds with those obtained or calculated from literature and analyzing with Taft's correlation as well.This study demonstrates that the SFS competition kinetics method can measure the chlorination rate constants of a test compound rapidly and accurately.ª 2014 Elsevier Ltd. All rights reserved. IntroductionChlorine is the most widely used chemical disinfectant around the world. It is cheap, stable and effective against many pathogens including bacteria and viruses. Hence, despite the formation of harmful chlorinated disinfection byproducts, chlorine will still act as a primary disinfectant in many countries. In recent years, the transformation and fate of various organic micropollutants during water chlorination have attracted increasing attentions (Deborde and von Gunten, 2008;Sharma, 2008;Sedlak and von Gunten, 2011). As a prerequisite, the kinetic rate constants of a micropollutant reacting towards chlorine should be determined, * Corresponding author. Tel.: þ86 10 62849128; fax: þ86 10 62923541. E-mail address: hjliu@rcees.ac.cn (H. Liu).Available online at www.sciencedirect.com ScienceDirect journal homepage: www.else vier.com/locate /wa tres w a t e r r e s e a r c h 5 5 ( 2 0 1 4 ) 1 2 6 e1 3 2 0043-1354/ ª

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The Acid Ionization Constant of HOCl from 5 to 35°

Cited by 883 publications

References 2 publications

Effect of pH on the formation of disinfection byproducts in swimming pool water – Is less THM better?

Effect of pH on the formation of disinfection byproducts in swimming pool water – Is less THM better?

Chlorination and oxidation of heparin and hyaluronan by hypochlorous acid and hypochlorite anions: effect of sulfate groups on reaction pathways and kinetics

Determination of rapid chlorination rate constants by a stopped-flow spectrophotometric competition kinetics method

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