Hypochlorous acid

Hypochlorous acid

Hydrogen, H    Oxygen, O    Chlorine, Cl
Names
IUPAC name Hypochlorous acid
Other names Chloranol Chloric(I) acid Chlorine hydroxide Chlorooxidane Hydrogen hypochlorite Hypochloric acid Hydroxidochlorine
Identifiers
CAS Number	7790-92-3  Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:24757  Y
ChemSpider	22757  Y
ECHA InfoCard	100.029.302
EC Number	232-232-5
PubChem CID	24341
UNII	712K4CDC10  Y
CompTox Dashboard (EPA)	DTXSID3036737
InChI InChI=1S/ClHO/c1-2/h2H Y Key: QWPPOHNGKGFGJK-UHFFFAOYSA-N Y InChI=1/ClHO/c1-2/h2H Key: QWPPOHNGKGFGJK-UHFFFAOYAT
SMILES OCl
Properties
Chemical formula	HOCl
Molar mass	52.46 g·mol−1
Appearance	Colorless aqueous solution
Density	Variable
Solubility in water	Soluble
Acidity (pKa)	7.53 [1]
Conjugate base	Hypochlorite
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	corrosive, oxidizing agent
GHS labelling:
Hazard statements	H320, H335
Precautionary statements	P301+P330+P331, P302+P352, P304+P340, P305+P351+P338
NFPA 704 (fire diamond)	3 0 4 OX
Safety data sheet (SDS)	chemfresh.com
Related compounds
Other anions	Hypofluorous acid Hypobromous acid Hypoiodous acid
Related compounds	Dichlorine monoxide Chlorine monoxide Hypochlorite Lithium hypochlorite Sodium hypochlorite Potassium hypochlorite Calcium hypochlorite Barium hypochlorite Silver hypochlorite Methyl hypochlorite tert-Butyl hypochlorite Acetyl hypochlorite Chlorine
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y  verify  (what is  YN ?) Infobox references

Hypochlorous acid is an inorganic compound with the chemical formula Cl O H , also written as HClO, HOCl, or ClHO. ^{[2] [3]} Its structure is H−O−Cl. It is an acid that forms when chlorine dissolves in water, and itself partially dissociates, forming hypochlorite anion, ClO⁻. HClO and ClO⁻ are oxidizers, and the primary disinfection agents of chlorine solutions. ^[4] HClO cannot be isolated from these solutions due to rapid equilibration with its precursor, chlorine.

Because of its strong antimicrobial properties, the related compounds sodium hypochlorite (NaOCl) and calcium hypochlorite (Ca(OCl)₂) are ingredients in many commercial bleaches, deodorants, and disinfectants. ^[5] The white blood cells of mammals, such as humans, also contain hypochlorous acid as a tool against foreign bodies. ^[6] In living organisms, HOCl is generated by the reaction of hydrogen peroxide with chloride ions under the catalysis of the heme enzyme myeloperoxidase (MPO). ^[7]

Like many other disinfectants, hypochlorous acid solutions will destroy pathogens, such as COVID-19, absorbed on surfaces. ^[8] In low concentrations, such solutions can serve to disinfect open wounds. ^[9]

History

Hypochlorous acid was discovered in 1834 by the French chemist Antoine Jérôme Balard (1802–1876) by adding, to a flask of chlorine gas, a dilute suspension of mercury(II) oxide in water. ^[10] He also named the acid and its compounds. ^[11]

Despite being relatively easy to make, it is difficult to maintain a stable hypochlorous acid solution. It is not until recent years that scientists have been able to cost-effectively produce and maintain hypochlorous acid water for stable commercial use.

Uses

• In organic synthesis, HClO converts alkenes to chlorohydrins. ^[12]
• In biology, hypochlorous acid is generated in activated neutrophils by myeloperoxidase-mediated peroxidation of chloride ions, and contributes to the destruction of bacteria. ^{[13] [14] [15]}
• In medicine, hypochlorous acid water has been used as a disinfectant and sanitiser. ^{[6] [9] [5]}
• In wound care, ^{[16] [17] [18]} and as of early 2016 the U.S. Food and Drug Administration has approved products whose main active ingredient is hypochlorous acid for use in treating wounds and various infections in humans and pets. It is also FDA-approved as a preservative for saline solutions.
• In disinfection, it has been used in the form of liquid spray, wet wipes and aerosolised application. Recent studies have shown hypochlorous acid water to be suitable for fog and aerosolised application for disinfection chambers and suitable for disinfecting indoor settings such as offices, hospitals and healthcare clinics. ^[19]
• In food service and water distribution, specialized equipment to generate weak solutions of HClO from water and salt is sometimes used to generate adequate quantities of safe (unstable) disinfectant to treat food preparation surfaces and water supplies. ^{[20] [21]} It is also commonly used in restaurants due to its non-flammable and nontoxic characteristics.
• In water treatment, hypochlorous acid is the active sanitizer in hypochlorite-based products (e.g. used in swimming pools). ^[22]
• Similarly, in ships and yachts, marine sanitation devices ^[23] use electricity to convert seawater into hypochlorous acid to disinfect macerated faecal waste before discharge into the sea.
• In deodorization, hypochlorous acid has been tested to remove up to 99% of foul odours including garbage, rotten meat, toilet, stool, and urine odours.^{[ citation needed ]}

Formation, stability and reactions

Addition of chlorine to water gives both hydrochloric acid (HCl) and hypochlorous acid (HClO): ^[24]

Cl₂ + H₂O ⇌ HClO + HCl

Cl₂ + 4 OH⁻ ⇌ 2 ClO⁻ + 2 H₂O + 2 e⁻

Cl₂ + 2 e⁻ ⇌ 2 Cl⁻

When acids are added to aqueous salts of hypochlorous acid (such as sodium hypochlorite in commercial bleach solution), the resultant reaction is driven to the left, and chlorine gas is formed. Thus, the formation of stable hypochlorite bleaches is facilitated by dissolving chlorine gas into basic water solutions, such as sodium hydroxide.

The acid can also be prepared by dissolving dichlorine monoxide in water; under standard aqueous conditions, anhydrous hypochlorous acid is currently impossible to prepare due to the readily reversible equilibrium between it and its anhydride: ^[25]

2 HClO ⇌ Cl₂O + H₂O, K = 3.55 × 10⁻³ dm³/mol (at 0 °C)

The presence of light or transition metal oxides of copper, nickel, or cobalt accelerates the exothermic^{[ dubious ]} decomposition into hydrochloric acid and oxygen: ^[25]

2 Cl₂ + 2 H₂O → 4 HCl + O₂

Fundamental reactions

In aqueous solution, hypochlorous acid partially dissociates into the anion hypochloriteClO⁻:

HClO ⇌ ClO⁻ + H⁺

Salts of hypochlorous acid are called hypochlorites. One of the best-known hypochlorites is NaClO, the active ingredient in bleach.

HClO is a stronger oxidant than chlorine under standard conditions.

2 HClO(aq) + 2 H⁺ + 2 e⁻ ⇌ Cl₂(g) + 2 H₂O, E = +1.63 V

HClO reacts with HCl to form chlorine:

HClO + HCl → H₂O + Cl₂

HClO reacts with ammonia to form monochloramine:

NH₃ + HClO → NH₂Cl + H₂O

HClO can also react with organic amines, forming N-chloroamines.

Hypochlorous acid exists in equilibrium with its anhydride, dichlorine monoxide. ^[25]

2 HClO ⇌ Cl₂O + H₂O, K = 3.55 × 10⁻³ dm³/mol (at 0 °C)

Reactivity of HClO with biomolecules

Hypochlorous acid reacts with a wide variety of biomolecules, including DNA, RNA, ^{[15] [26] [27] [28]} fatty acid groups, cholesterol ^{[29] [30] [31] [32] [33] [34] [35] [36]} and proteins. ^{[32] [37] [38] [39] [40] [41] [42]}

Reaction with protein sulfhydryl groups

Knox et al. ^[40] first noted that HClO is a sulfhydryl inhibitor that, in sufficient quantity, could completely inactivate proteins containing sulfhydryl groups. This is because HClO oxidises sulfhydryl groups, leading to the formation of disulfide bonds ^[43] that can result in crosslinking of proteins. The HClO mechanism of sulfhydryl oxidation is similar to that of monochloramine, and may only be bacteriostatic, because once the residual chlorine is dissipated, some sulfhydryl function can be restored. ^[39] One sulfhydryl-containing amino acid can scavenge up to four molecules of HClO. ^[42] Consistent with this, it has been proposed that sulfhydryl groups of sulfur-containing amino acids can be oxidized a total of three times by three HClO molecules, with the fourth reacting with the α-amino group. The first reaction yields sulfenic acid (R−S−OH) then sulfinic acid (R−S(=O)−OH) and finally R−S(=O)₂−OH. Sulfenic acids form disulfides with another protein sulfhydryl group, causing cross-linking and aggregation of proteins. Sulfinic acid and R−S(=O)₂−OH derivatives are produced only at high molar excesses of HClO, and disulfides are formed primarily at bacteriocidal levels. ^[28] Disulfide bonds can also be oxidized by HClO to sulfinic acid. ^[43] Because the oxidation of sulfhydryls and disulfides evolves hydrochloric acid, ^[28] this process results in the depletion HClO.

Reaction with protein amino groups

Hypochlorous acid reacts readily with amino acids that have amino group side-chains, with the chlorine from HClO displacing a hydrogen, resulting in an organic chloramine. ^[44] Chlorinated amino acids rapidly decompose, but protein chloramines are longer-lived and retain some oxidative capacity. ^{[14] [42]} Thomas et al. ^[14] concluded from their results that most organic chloramines decayed by internal rearrangement and that fewer available NH2 groups promoted attack on the peptide bond, resulting in cleavage of the protein. McKenna and Davies ^[45] found that 10 mM or greater HClO is necessary to fragment proteins in vivo. Consistent with these results, it was later proposed that the chloramine undergoes a molecular rearrangement, releasing HCl and ammonia to form an aldehyde. ^[46] The aldehyde group can further react with another amino group to form a Schiff base, causing cross-linking and aggregation of proteins. ^[32]

Reaction with DNA and nucleotides

Hypochlorous acid reacts slowly with DNA and RNA as well as all nucleotides in vitro. ^{[26] [47]} GMP is the most reactive because HClO reacts with both the heterocyclic NH group and the amino group. In similar manner, TMP with only a heterocyclic NH group that is reactive with HClO is the second-most reactive. AMP and CMP, which have only a slowly reactive amino group, are less reactive with HClO. ^[47] UMP has been reported to be reactive only at a very slow rate. ^{[15] [26]} The heterocyclic NH groups are more reactive than amino groups, and their secondary chloramines are able to donate the chlorine. ^[28] These reactions likely interfere with DNA base pairing, and, consistent with this, Prütz ^[47] has reported a decrease in viscosity of DNA exposed to HClO similar to that seen with heat denaturation. The sugar moieties are nonreactive and the DNA backbone is not broken. ^[47] NADH can react with chlorinated TMP and UMP as well as HClO. This reaction can regenerate UMP and TMP and results in the 5-hydroxy derivative of NADH. The reaction with TMP or UMP is slowly reversible to regenerate HClO. A second slower reaction that results in cleavage of the pyridine ring occurs when excess HClO is present. NAD⁺ is inert to HClO. ^{[28] [47]}

Reaction with lipids

Hypochlorous acid reacts with unsaturated bonds in lipids, but not saturated bonds, and the ClO⁻ ion does not participate in this reaction. This reaction occurs by hydrolysis with addition of chlorine to one of the carbons and a hydroxyl to the other. The resulting compound is a chlorohydrin. ^[29] The polar chlorine disrupts lipid bilayers and could increase permeability. ^[30] When chlorohydrin formation occurs in lipid bilayers of red blood cells, increased permeability occurs. Disruption could occur if enough chlorohydrin is formed. ^{[29] [35]} The addition of preformed chlorohydrin to red blood cells can affect permeability as well. ^[31] Cholesterol chlorohydrin have also been observed, ^{[30] [33]} but do not greatly affect permeability, and it is believed that Cl₂ is responsible for this reaction. ^[33] Hypochlorous acid also reacts with a subclass of glycerophospholipids called plasmalogens, yielding chlorinated fatty aldehydes which are capable of protein modification and may play a role in inflammatory processes such as platelet aggregation and the formation of neutrophil extracellular traps. ^{[48] [49] [50]}

Mode of disinfectant action

E. coli exposed to hypochlorous acid lose viability in less than 0.1 seconds due to inactivation of many vital systems. ^{[24] [51] [52] [53] [54]} Hypochlorous acid has a reported LD₅₀ of 0.0104–0.156 ppm ^[55] and 2.6 ppm caused 100% growth inhibition in 5 minutes. ^[45] However, the concentration required for bactericidal activity is also highly dependent on bacterial concentration. ^[40]

Inhibition of glucose oxidation

In 1948, Knox et al. ^[40] proposed the idea that inhibition of glucose oxidation is a major factor in the bacteriocidal nature of chlorine solutions. They proposed that the active agent or agents diffuse across the cytoplasmic membrane to inactivate key sulfhydryl-containing enzymes in the glycolytic pathway. This group was also the first to note that chlorine solutions (HClO) inhibit sulfhydryl enzymes. Later studies have shown that, at bacteriocidal levels, the cytosol components do not react with HClO. ^[56] In agreement with this, McFeters and Camper ^[57] found that aldolase, an enzyme that Knox et al. ^[40] proposes would be inactivated, was unaffected by HClO in vivo. It has been further shown that loss of sulfhydryls does not correlate with inactivation. ^[39] That leaves the question concerning what causes inhibition of glucose oxidation. The discovery that HClO blocks induction of β-galactosidase by added lactose ^[58] led to a possible answer to this question. The uptake of radiolabeled substrates by both ATP hydrolysis and proton co-transport may be blocked by exposure to HClO preceding loss of viability. ^[56] From this observation, it proposed that HClO blocks uptake of nutrients by inactivating transport proteins. ^{[38] [56] [57] [59]} The question of loss of glucose oxidation has been further explored in terms of loss of respiration. Venkobachar et al. ^[60] found that succinic dehydrogenase was inhibited in vitro by HClO, which led to the investigation of the possibility that disruption of electron transport could be the cause of bacterial inactivation. Albrich et al. ^[15] subsequently found that HClO destroys cytochromes and iron-sulfur clusters and observed that oxygen uptake is abolished by HClO and adenine nucleotides are lost. It was also observed that irreversible oxidation of cytochromes paralleled the loss of respiratory activity. One way of addressing the loss of oxygen uptake was by studying the effects of HClO on succinate-dependent electron transport. ^[61] Rosen et al. ^[54] found that levels of reductable cytochromes in HClO-treated cells were normal, and these cells were unable to reduce them. Succinate dehydrogenase was also inhibited by HClO, stopping the flow of electrons to oxygen. Later studies ^[52] revealed that Ubiquinol oxidase activity ceases first, and the still-active cytochromes reduce the remaining quinone. The cytochromes then pass the electrons to oxygen, which explains why the cytochromes cannot be reoxidized, as observed by Rosen et al. ^[54] However, this line of inquiry was ended when Albrich et al. ^[37] found that cellular inactivation precedes loss of respiration by using a flow mixing system that allowed evaluation of viability on much smaller time scales. This group found that cells capable of respiring could not divide after exposure to HClO.

Depletion of adenine nucleotides

Having eliminated loss of respiration, Albrich et al. ^[37] proposes that the cause of death may be due to metabolic dysfunction caused by depletion of adenine nucleotides. Barrette et al. ^[58] studied the loss of adenine nucleotides by studying the energy charge of HClO-exposed cells and found that cells exposed to HClO were unable to step up their energy charge after addition of nutrients. The conclusion was that exposed cells have lost the ability to regulate their adenylate pool, based on the fact that metabolite uptake was only 45% deficient after exposure to HClO and the observation that HClO causes intracellular ATP hydrolysis. It was also confirmed that, at bacteriocidal levels of HClO, cytosolic components are unaffected. So it was proposed that modification of some membrane-bound protein results in extensive ATP hydrolysis, and this, coupled with the cells inability to remove AMP from the cytosol, depresses metabolic function. One protein involved in loss of ability to regenerate ATP has been found to be ATP synthetase. ^[38] Much of this research on respiration reconfirms the observation that relevant bacteriocidal reactions take place at the cell membrane. ^{[38] [58] [62]}

Inhibition of DNA replication

Recently it has been proposed that bacterial inactivation by HClO is the result of inhibition of DNA replication. When bacteria are exposed to HClO, there is a precipitous decline in DNA synthesis that precedes inhibition of protein synthesis, and closely parallels loss of viability. ^{[45] [63]} During bacterial genome replication, the origin of replication (oriC in E. coli) binds to proteins that are associated with the cell membrane, and it was observed that HClO treatment decreases the affinity of extracted membranes for oriC, and this decreased affinity also parallels loss of viability. A study by Rosen et al. ^[64] compared the rate of HClO inhibition of DNA replication of plasmids with different replication origins and found that certain plasmids exhibited a delay in the inhibition of replication when compared to plasmids containing oriC. Rosen's group proposed that inactivation of membrane proteins involved in DNA replication are the mechanism of action of HClO.

Protein unfolding and aggregation

HClO is known to cause post-translational modifications to proteins, the notable ones being cysteine and methionine oxidation. A recent examination of HClO's bactericidal role revealed it to be a potent inducer of protein aggregation. ^[65] Hsp33, a chaperone known to be activated by oxidative heat stress, protects bacteria from the effects of HClO by acting as a holdase, effectively preventing protein aggregation. Strains of Escherichia coli and Vibrio cholerae lacking Hsp33 were rendered especially sensitive to HClO. Hsp33 protected many essential proteins from aggregation and inactivation due to HClO, which is a probable mediator of HClO's bactericidal effects.

Hypochlorites

Main article: Hypochlorite

Hypochlorites are the salts of hypochlorous acid; commercially important hypochlorites are calcium hypochlorite and sodium hypochlorite.

Production of hypochlorites using electrolysis

See also: Chloralkali process

Solutions of hypochlorites can be produced in-situ by electrolysis of an aqueous sodium chloride solution in both batch and flow processes. ^[66] The composition of the resulting solution depends on the pH at the anode. In acid conditions the solution produced will have a high hypochlorous acid concentration, but will also contain dissolved gaseous chlorine, which can be corrosive, at a neutral pH the solution will be around 75% hypochlorous acid and 25% hypochlorite. Some of the chlorine gas produced will dissolve forming hypochlorite ions. Hypochlorites are also produced by the disproportionation of chlorine gas in alkaline solutions.

Safety

HClO is classified as Non-Hazardous by the Environmental Protection Agency in the US. As any oxidising agent it can be corrosive or irritant depending on its concentration and pH.

In a clinical test, hypochlorous acid water was tested for eye irritation, skin irritation, and toxicity. The test concluded that it was non-toxic and nonirritating to the eye and skin. ^[67]

In a 2017 study, a saline hygiene solution preserved with pure hypochlorous acid was shown to reduce the bacterial load significantly without altering the diversity of bacterial species on the eyelids. After 20 minutes of treatment, there was >99% reduction of the Staphylococci bacteria. ^[68]

Commercialisation

For disinfection, despite being discovered a long time ago, the stability of hypochlorous acid water is difficult to maintain. In solution, the active compounds quickly deteriorate back into salt water, losing its disinfecting capability, which makes it difficult to transport for wide use. Despite its stronger disinfecting capabilities, it is less commonly used as a disinfectant compared to bleach and alcohol due to cost.

Technological developments have reduced manufacturing costs and allow for manufacturing and bottling of hypochlorous acid water for home and commercial use. However, most hypochlorous acid water has a short shelf life. Storing away from heat and direct sunlight can help slow the deterioration. The further development of continuous flow electrochemical cells has been implemented in new products, allowing the commercialisation of domestic and industrial continuous flow devices for the in-situ generation of hypochlorous acid for disinfection purposes. ^[69]

See also

• Dichlorine monoxide: the corresponding acidic oxide
• Hypofluorous acid
• Perchloric acid

References

1. Harris, Daniel C. (2009). Exploring Chemical Analysis (Fourth ed.). p. 538.
2. "Hypochlorous acid". CAS Common Chemistry. CAS, a division of the American Chemical Society, n.d. CAS RN: 7790-92-3. Retrieved 2022-04-12.
3. "hypochlorous acid". Chemical Entities of Biological Interest . European Bioinformatics Institute. CHEBI:24757. Retrieved 2022-04-12.
4. Sansebastiano, G. et al. Page 262 in Food Safety: A Practical and Case Study Approach (Ed: R. J. Marshall) 2006, Springer Science & Business Media, Berlin.
5. Block, Michael S.; Rowan, Brian G. (September 2020). "Hypochlorous Acid: A Review". Journal of Oral and Maxillofacial Surgery. 78 (9): 1461–1466. doi:10.1016/j.joms.2020.06.029. ISSN   0278-2391. PMC   7315945 . PMID   32653307.
6. "Treating Chronic Wounds With Hypochlorous Acid Disrupts Biofilm". Today's Wound Clinic. Retrieved 2021-02-08.
7. Ghoshal K, et al. (July 2016). "A novel sensor to estimate the prevalence of hypochlorous (HOCl) toxicity in individuals with type 2 diabetes and dyslipidemia". Clinica Chimica Acta. 458: 144–153. doi:10.1016/j.cca.2016.05.006. PMID   27178483.
8. US EPA, OCSPP (2020-03-13). "List N: Disinfectants for Coronavirus (COVID-19)". US EPA. Retrieved 2021-02-08.
9. "Pure Hypochlorous Acid: A Primer on pH and Wound Solutions". WoundSource. 2020-11-05. Retrieved 2021-02-08..
10. See:
    • Balard, A. J. (1834). "Recherches sur la nature des combinaisons décolorantes du chlore" [Investigations into the nature of bleaching compounds of chlorine]. Annales de Chimie et de Physique. 2nd series (in French). 57: 225–304. From p. 246: " … il est beaucoup plus commode … environ d'eau distillée." ( … it is much easier to pour, into flasks full of chlorine, red mercury oxide [that has been] reduced to a fine powder by grinding and diluted in about twelve times its weight of distilled water.)
    • Graham, Thomas (1840). Elements of Chemistry. Vol. 4. London, England: H. Baillière. p. 367.
11. (Balard, 1834), p. 293. From p. 293: "Quelle dénomination … appelées hypochlorites." (What name should one assign to this compound? It's obvious that that of "chlorous acid" can hardly be retained for it, and that it is more appropriate to call it hypochlorous acid, a name that recalls its similarity of composition with hyposulfurous acid, hypophosphorous acid, etc., [which are] formed, like it, from 1 equivalent of their radical and 1 equivalent of oxygen. Its compounds will be called hypochlorites.)
12. Unangst, P. C. "Hypochlorous Acid" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. doi : 10.1002/047084289X.rh073
13. Harrison, J. E.; J. Schultz (1976). "Studies on the chlorinating activity of myeloperoxidase". Journal of Biological Chemistry. 251 (5): 1371–1374. doi: 10.1016/S0021-9258(17)33749-3 . PMID   176150.
14. Thomas, E. L. (1979). "Myeloperoxidase, hydrogen peroxide, chloride antimicrobial system: Nitrogen-chlorine derivatives of bacterial components in bactericidal action against Escherichia coli". Infect. Immun. 23 (2): 522–531. doi:10.1128/IAI.23.2.522-531.1979. PMC   414195 . PMID   217834.
15. Albrich, J. M., C. A. McCarthy, and J. K. Hurst (1981). "Biological reactivity of hypochlorous acid: Implications for microbicidal mechanisms of leukocyte myeloperoxidase". Proc. Natl. Acad. Sci. 78 (1): 210–214. Bibcode:1981PNAS...78..210A. doi: 10.1073/pnas.78.1.210 . PMC   319021 . PMID   6264434.
16. Wang L et al. "Hypochlorous acid as a potential wound care agent. Part I Stabilized hypochlorous acid: a component of the inorganic armamentarium of innate immunity". J Burns and Wounds 2007; April: 65–79.
17. Robson MC et al. "Hypochlorous acid as a potential wound care agent. Part II Stabilized hypochlorous acid: its role in decreasing tissue bacterial bioburden and overcoming the inhibition of infection on wound healing". Journal of Burns and Wounds 2007; April: 80–90.
18. Selkon, JB; et al. (2006). "Evaluation of hypochlorous acid washes in the treatment of venous leg ulcers". J Wound Care. 2006 (15): 33–37. doi:10.12968/jowc.2006.15.1.26861. PMID   16669304.
19. Nguyen, Kate; Bui, Dinh; Hashemi, Mahak; Hocking, Dianna M; Mendis, Priyan; Strugnell, Richard A; Dharmage, Shyamali C (2021-01-22). "The Potential Use of Hypochlorous Acid and a Smart Prefabricated Sanitising Chamber to Reduce Occupation-Related COVID-19 Exposure". Risk Management and Healthcare Policy. 14: 247–252. doi: 10.2147/RMHP.S284897 . ISSN   1179-1594. PMC   7837568 . PMID   33519249.
20. "Disinfection of Facility H₂O" Archived 2019-01-22 at the Wayback Machine .
21. "Water Works: Hyatt's New Disinfectant/Cleaner Comes from the Tap", Bloomberg Businessweek.
22. Gonick, Larry; Criddle, Craig (2005-05-03). "Chapter 9 Acid Basics" . The cartoon guide to chemistry (1st ed.). HarperResource. p.  189. ISBN   9780060936778. Similarly, we add HOCl to swimming pools to kill bacteria.
23. e.g. Raritan Electro Scan device
24. Fair, G. M., J. Corris, S. L. Chang, I. Weil, and R. P. Burden (1948). "The behavior of chlorine as a water disinfectant". J. Am. Water Works Assoc. 40 (10): 1051–1061. doi:10.1002/j.1551-8833.1948.tb15055.x. PMID   18145494.
25. Inorganic chemistry, Egon Wiberg, Nils Wiberg, Arnold Frederick Holleman, "Hypochlorous acid", p. 442, section 4.3.1
26. Dennis, W. H., Jr, V. P. Olivieri, and C. W. Krusé (1979). "The reaction of nucleotides with aqueous hypochlorous acid". Water Res. 13 (4): 357–362. Bibcode:1979WatRe..13..357D. doi:10.1016/0043-1354(79)90023-X.
27. Jacangelo, J. G., and V. P. Olivieri. 1984. Aspects of the mode of action of monochloramine. In R. L. Jolley, R. J. Bull, W. P. Davis, S. Katz, M. H. Roberts, Jr., and V. A. Jacobs (ed.), Water Chlorination, vol. 5. Lewis Publishers, Inc., Williamsburg.
28. Prütz, WA (1998). "Interactions of hypochlorous acid with pyrimidine nucleotides, and secondary reactions of chlorinated pyrimidines with GSH, NADH, and other substrates". Archives of Biochemistry and Biophysics. 349 (1): 183–91. doi:10.1006/abbi.1997.0440. PMID   9439597.
29. Arnhold, J; Panasenko, OM; Schiller, J; Vladimirov, YuA; Arnold, K (1995). "The action of hypochlorous acid on phosphatidylcholine liposomes in dependence on the content of double bonds. Stoichiometry and NMR analysis". Chemistry and Physics of Lipids. 78 (1): 55–64. doi:10.1016/0009-3084(95)02484-Z. PMID   8521532.
30. Carr, AC; Van Den Berg, JJ; Winterbourn, CC (1996). "Chlorination of cholesterol in cell membranes by hypochlorous acid". Archives of Biochemistry and Biophysics. 332 (1): 63–9. doi:10.1006/abbi.1996.0317. PMID   8806710.
31. Carr, AC; Vissers, MC; Domigan, NM; Winterbourn, CC (1997). "Modification of red cell membrane lipids by hypochlorous acid and haemolysis by preformed lipid chlorohydrins". Redox Report: Communications in Free Radical Research. 3 (5–6): 263–71. doi: 10.1080/13510002.1997.11747122 . PMID   9754324.
32. Hazell, L. J., J. V. D. Berg, and R. Stocker (1994). "Oxidation of low density lipoprotein by hypochlorite causes aggregation that is mediated by modification of lysine residues rather than lipid oxidation". Biochem. J. 302 (Pt 1): 297–304. doi:10.1042/bj3020297. PMC   1137223 . PMID   8068018.
33. Hazen, SL; Hsu, FF; Duffin, K; Heinecke, JW (1996). "Molecular chlorine generated by the myeloperoxidase-hydrogen peroxide-chloride system of phagocytes converts low density lipoprotein cholesterol into a family of chlorinated sterols". The Journal of Biological Chemistry. 271 (38): 23080–8. doi: 10.1074/jbc.271.38.23080 . PMID   8798498.
34. Vissers, MC; Carr, AC; Chapman, AL (1998). "Comparison of human red cell lysis by hypochlorous and hypobromous acids: insights into the mechanism of lysis". The Biochemical Journal. 330 (1): 131–8. doi:10.1042/bj3300131. PMC   1219118 . PMID   9461501.
35. Vissers, MC; Stern, A; Kuypers, F; Van Den Berg, J; Winterbourn, CC (1994). "Membrane changes associated with lysis of red blood cells by hypochlorous acid". Free Radical Biology & Medicine. 16 (6): 703–12. doi:10.1016/0891-5849(94)90185-6. PMID   8070673.
36. Winterbourn, CC; Van Den Berg, JJ; Roitman, E; Kuypers, FA (1992). "Chlorohydrin formation from unsaturated fatty acids reacted with hypochlorous acid". Archives of Biochemistry and Biophysics. 296 (2): 547–55. doi:10.1016/0003-9861(92)90609-Z. PMID   1321589.
37. Albrich, JM; Hurst, JK (1982). "Oxidative inactivation of Escherichia coli by hypochlorous acid. Rates and differentiation of respiratory from other reaction sites". FEBS Letters. 144 (1): 157–61. doi: 10.1016/0014-5793(82)80591-7 . PMID   6286355. S2CID   40223719.
38. Barrette Jr, WC; Hannum, DM; Wheeler, WD; Hurst, JK (1989). "General mechanism for the bacterial toxicity of hypochlorous acid: abolition of ATP production". Biochemistry. 28 (23): 9172–8. doi:10.1021/bi00449a032. PMID   2557918.
39. Jacangelo, J; Olivieri, V; Kawata, K (1987). "Oxidation of sulfhydryl groups by monochloramine". Water Research. 21 (11): 1339–1344. Bibcode:1987WatRe..21.1339J. doi:10.1016/0043-1354(87)90007-8.
40. Knox, WE; Stumpf, PK; Green, DE; Auerbach, VH (1948). "The Inhibition of Sulfhydryl Enzymes as the Basis of the Bactericidal Action of Chlorine". Journal of Bacteriology. 55 (4): 451–8. doi:10.1128/JB.55.4.451-458.1948. PMC   518466 . PMID   16561477.
41. Vissers, MC; Winterbourn, CC (1991). "Oxidative damage to fibronectin. I. The effects of the neutrophil myeloperoxidase system and HOCl". Archives of Biochemistry and Biophysics. 285 (1): 53–9. doi:10.1016/0003-9861(91)90327-F. PMID   1846732.
42. Winterbourn, CC (1985). "Comparative reactivities of various biological compounds with myeloperoxidase-hydrogen peroxide-chloride, and similarity of the oxidant to hypochlorite". Biochimica et Biophysica Acta (BBA) - General Subjects. 840 (2): 204–10. doi:10.1016/0304-4165(85)90120-5. PMID   2986713.
43. Pereira, WE; Hoyano, Y; Summons, RE; Bacon, VA; Duffield, AM (1973). "Chlorination studies. II. The reaction of aqueous hypochlorous acid with alpha-amino acids and dipeptides". Biochimica et Biophysica Acta. 313 (1): 170–80. doi:10.1016/0304-4165(73)90198-0. PMID   4745674.
44. Dychdala, G. R. 1991. Chlorine and chlorine compounds, pp. 131–151. In S. S. Block (ed.), Disinfection, Sterilization and Preservation. Lea & Febiger, Philadelphia. ISBN   0-683-30740-1
45. McKenna, SM; Davies, KJ (1988). "The inhibition of bacterial growth by hypochlorous acid. Possible role in the bactericidal activity of phagocytes". The Biochemical Journal. 254 (3): 685–92. doi:10.1042/bj2540685. PMC   1135139 . PMID   2848494.
46. Hazen, SL; D'Avignon, A; Anderson, MM; Hsu, FF; Heinecke, JW (1998). "Human neutrophils employ the myeloperoxidase-hydrogen peroxide-chloride system to oxidize alpha-amino acids to a family of reactive aldehydes. Mechanistic studies identifying labile intermediates along the reaction pathway". The Journal of Biological Chemistry. 273 (9): 4997–5005. doi: 10.1074/jbc.273.9.4997 . PMID   9478947.
47. Prütz, WA (1996). "Hypochlorous acid interactions with thiols, nucleotides, DNA, and other biological substrates". Archives of Biochemistry and Biophysics. 332 (1): 110–20. doi:10.1006/abbi.1996.0322. PMID   8806715.
48. Albert, Carolyn J.; Crowley, Jan R.; Hsu, Fong-Fu; Thukkani, Arun K.; Ford, David A. (June 2001). "Reactive Chlorinating Species Produced by Myeloperoxidase Target the Vinyl Ether Bond of Plasmalogens". Journal of Biological Chemistry. 276 (26): 23733–23741. doi: 10.1074/jbc.M101447200 . PMID   11301330.
49. Yu, Hong; Wang, Meifang; Wang, Derek; Kalogeris, Theodore J.; McHowat, Jane; Ford, David A.; Korthuis, Ronald J. (January 2019). "Chlorinated Lipids Elicit Inflammatory Responses in vitro and in vivo". Shock. 51 (1): 114–122. doi:10.1097/SHK.0000000000001112. PMC   6070441 . PMID   29394241.
50. Palladino, ElisaN.D.; Katunga, Lalage A.; Kolar, Grant R.; Ford, David A. (August 2018). "2-Chlorofatty acids: lipid mediators of neutrophil extracellular trap formation". Journal of Lipid Research. 59 (8): 1424–1432. doi: 10.1194/jlr.M084731 . PMC   6071778 . PMID   29739865.
51. Rakita, RM; Michel, BR; Rosen, H (1990). "Differential inactivation of Escherichia coli membrane dehydrogenases by a myeloperoxidase-mediated antimicrobial system". Biochemistry. 29 (4): 1075–80. doi:10.1021/bi00456a033. PMID   1692736.
52. Rakita, RM; Michel, BR; Rosen, H (1989). "Myeloperoxidase-mediated inhibition of microbial respiration: damage to Escherichia coli ubiquinol oxidase". Biochemistry. 28 (7): 3031–6. doi:10.1021/bi00433a044. PMID   2545243.
53. Rosen, H.; S. J. Klebanoff (1985). "Oxidation of microbial iron-sulfur centers by the myeloperoxidase-H2O2-halide antimicrobial system". Infect. Immun. 47 (3): 613–618. doi:10.1128/IAI.47.3.613-618.1985. PMC   261335 . PMID   2982737.
54. Rosen, H., R. M. Rakita, A. M. Waltersdorph, and S. J. Klebanoff (1987). "Myeloperoxidase-mediated damage to the succinate oxidase system of Escherichia coli". J. Biol. Chem. 242: 15004–15010. doi: 10.1016/S0021-9258(18)48129-X .
55. Chesney, JA; Eaton, JW; Mahoney Jr, JR (1996). "Bacterial glutathione: a sacrificial defense against chlorine compounds". Journal of Bacteriology. 178 (7): 2131–5. doi:10.1128/jb.178.7.2131-2135.1996. PMC   177915 . PMID   8606194.
56. Morris, J. C. (1966). "The acid ionization constant of HClO from 5 to 35 °". J. Phys. Chem. 70 (12): 3798–3805. doi:10.1021/j100884a007.
57. McFeters, GA; Camper, AK (1983). Enumeration of indicator bacteria exposed to chlorine. Vol. 29. pp.  177–93. doi:10.1016/S0065-2164(08)70357-5. ISBN   978-0-12-002629-6. PMID   6650262.{{cite book}}: |journal= ignored (help)
58. Barrette Jr, WC; Albrich, JM; Hurst, JK (1987). "Hypochlorous acid-promoted loss of metabolic energy in Escherichia coli". Infection and Immunity. 55 (10): 2518–25. doi:10.1128/IAI.55.10.2518-2525.1987. PMC   260739 . PMID   2820883.
59. Camper, AK; McFeters, GA (1979). "Chlorine injury and the enumeration of waterborne coliform bacteria". Applied and Environmental Microbiology. 37 (3): 633–41. Bibcode:1979ApEnM..37..633C. doi:10.1128/AEM.37.3.633-641.1979. PMC   243267 . PMID   378130.
60. Venkobachar, C; Iyengar, L; Prabhakararao, A (1975). "Mechanism of disinfection☆". Water Research. 9 (1): 119–124. Bibcode:1975WatRe...9..119V. doi:10.1016/0043-1354(75)90160-8.
61. Hurst, JK; Barrette Jr, WC; Michel, BR; Rosen, H (1991). "Hypochlorous acid and myeloperoxidase-catalyzed oxidation of iron-sulfur clusters in bacterial respiratory dehydrogenases". European Journal of Biochemistry. 202 (3): 1275–82. doi: 10.1111/j.1432-1033.1991.tb16500.x . PMID   1662610.
62. Rosen, H; Klebanoff, SJ (1982). "Oxidation of Escherichia coli iron centers by the myeloperoxidase-mediated microbicidal system". The Journal of Biological Chemistry. 257 (22): 13731–35. doi: 10.1016/S0021-9258(18)33509-9 . PMID   6292201.
63. Rosen, H; Orman, J; Rakita, RM; Michel, BR; Vandevanter, DR (1990). "Loss of DNA-membrane interactions and cessation of DNA synthesis in myeloperoxidase-treated Escherichia coli". Proceedings of the National Academy of Sciences of the United States of America. 87 (24): 10048–52. Bibcode:1990PNAS...8710048R. doi: 10.1073/pnas.87.24.10048 . PMC   55312 . PMID   2175901.
64. Rosen, H; Michel, BR; Vandevanter, DR; Hughes, JP (1998). "Differential effects of myeloperoxidase-derived oxidants on Escherichia coli DNA replication". Infection and Immunity. 66 (6): 2655–9. doi:10.1128/IAI.66.6.2655-2659.1998. PMC   108252 . PMID   9596730.
65. Winter, J.; Ilbert, M.; Graf, P.C.F.; Özcelik, D.; Jakob, U. (2008). "Bleach Activates a Redox-Regulated Chaperone by Oxidative Protein Unfolding". Cell. 135 (4): 691–701. doi:10.1016/j.cell.2008.09.024. PMC   2606091 . PMID   19013278.
66. Migliarina, Franco; Ferro, Sergio (December 2014). "A Modern Approach to Disinfection, as Old as the Evolution of Vertebrates". Healthcare. 2 (4): 516–526. doi: 10.3390/healthcare2040516 . PMC   4934573 . PMID   27429291.
67. Wang, L; Bassiri, M; Najafi, R; Najafi, K; Yang, J; Khosrovi, B; Hwong, W; Barati, E; Belisle, B; Celeri, C; Robson, MC (2007-04-11). "Hypochlorous Acid as a Potential Wound Care Agent". Journal of Burns and Wounds. 6: e5. ISSN   1554-0766. PMC   1853323 . PMID   17492050.
68. Stroman, D. W; Mintun, K; Epstein, A. B; Brimer, C. M; Patel, C. R; Branch, J. D; Najafi-Tagol, K (2017). "Reduction in bacterial load using hypochlorous acid hygiene solution on ocular skin". Clinical Ophthalmology. 11: 707–714. doi: 10.2147/OPTH.S132851 . PMC   5402722 . PMID   28458509.
69. "In situ generation: Active substances vs biocidal products". www.hse.gov.uk. Retrieved 2021-07-12.

External links

• National Pollutant Inventory – Chlorine
• Reuters – Mystery solved: How bleach kills germs
• "From Ground to Tap": a summary of the municipal tapwater treatment process