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Properties and Structure
- Boiling point of hydrogen peroxide is 150.2°C (302.4°F)
- Forms stable adducts with urea and sodium carbonate
- Can be used as a carrier in some reactions with triphenylphosphine oxide
- Has a nonplanar molecular structure with twisted C symmetry
- Exhibits chiral properties and enantiomerism
- O−O bond is a single bond with high rotational barriers for enantiomers
- Dihedral angle between O–H bonds is approximately 100°
- Molecular structures differ in gaseous and crystalline states due to hydrogen bonding
- Crystals of hydrogen peroxide are tetragonal with space group P422
- Enantiospecific interactions may have led to homochirality in RNA world
- Hydrogen peroxide has higher boiling point and melting point compared to analogues
- Analogues adopt similar skewed structures due to repulsion between lone pairs
- Hydrogen disulfide and diphosphane have weak hydrogen bonding and little chemical similarity
- Hydroxylamine crystallizes more readily due to strong hydrogen bonding
- Hydrogen peroxide exhibits unique properties among analogues
Aqueous solutions
- Forms eutectic mixture with freezing-point depression down to -56°C
- Boiling point of mixture is depressed in relation to pure water and pure hydrogen peroxide
- Density of aqueous solutions varies with concentration
- Most commonly available as solutions in water at 3% and 6% concentrations
- Commercial grades range from 70% to 98% and require special care in storage
Natural occurrence
- Produced by biological processes mediated by enzymes
- Detected in surface water, groundwater, and atmosphere
- Sea water contains 0.5 to 14μg/L of hydrogen peroxide, freshwater contains 1 to 30μg/L
- Concentrations in air vary depending on conditions such as season and altitude
- Assay can be used to measure hydrogen peroxide in biological systems
Production
- Hydrogen peroxide is manufactured using the anthraquinone process.
- The process involves reduction of an anthraquinone to anthrahydroquinone, followed by autoxidation.
- Most commercial processes use compressed air for oxidation.
- Effective recycling of extraction solvents and catalysts is crucial for the economics of the process.
- The net reaction for the anthraquinone-catalyzed process is: anthrahydroquinone + oxygen -> hydrogen peroxide + anthraquinone.
- In the past, hydrogen peroxide was prepared by hydrolysis of ammonium persulfate.
- Ammonium persulfate was obtained through the electrolysis of ammonium bisulfate in sulfuric acid.
- This method is no longer used industrially.
- Small amounts of hydrogen peroxide can be formed through electrolysis, photochemistry, and electric arc.
- A commercially viable route for hydrogen peroxide production involves the reaction of hydrogen with oxygen.
- However, direct processes often result in a dilute solution that is uneconomical for transportation.
- None of these alternative routes have reached industrial-scale synthesis yet.
Reactions
- Hydrogen peroxide is a stronger acid than water. Its pK value is 11.65.
- Hydrogen peroxide disproportionates to form water and oxygen.
- The reaction has a negative enthalpy change and a positive entropy change.
- Decomposition is accelerated by temperature, concentration, and pH.
- Alkaline conditions make hydrogen peroxide unstable.
- Various redox-active ions and compounds catalyze the decomposition.
- In acidic solutions, hydrogen peroxide is a powerful oxidizer.
- It can oxidize sulfite ions to sulfate ions.
- The oxidation potentials of hydrogen peroxide are dependent on the specific oxidizing agent.
- Under alkaline conditions, hydrogen peroxide acts as a reductant.
- It can reduce sodium hypochlorite and potassium permanganate, producing oxygen gas.
- This reduction reaction is a convenient method for preparing oxygen in the laboratory.
Hydrogen peroxide is a chemical compound with the formulaH2O2. In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3%–6% by weight) in water for consumer use, and in higher concentrations for industrial use. Concentrated hydrogen peroxide, or "high-test peroxide", decomposes explosively when heated and has been used both as a monopropellant and an oxidizer in rocketry.
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| Names | |||
|---|---|---|---|
| IUPAC name Hydrogen peroxide | |||
| Systematic IUPAC name Peroxol | |||
| Other names Dioxidane Oxidanyl Perhydroxic acid 0-hydroxyol Oxygenated water Peroxaan | |||
| Identifiers | |||
3D model (JSmol) | |||
| ChEBI | |||
| ChEMBL | |||
| ChemSpider | |||
| ECHA InfoCard | 100.028.878 | ||
| EC Number |
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| KEGG | |||
PubChem CID | |||
| RTECS number |
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| UNII | |||
| UN number | 2015 (>60% soln.) 2014 (20–60% soln.) 2984 (8–20% soln.) | ||
CompTox Dashboard (EPA) | |||
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| Properties | |||
| H2O2 | |||
| Molar mass | 34.014 g·mol−1 | ||
| Appearance | Very light blue liquid | ||
| Odor | slightly sharp | ||
| Density | 1.11 g/cm3 (20 °C, 30% (w/w) solution) 1.450 g/cm3 (20 °C, pure) | ||
| Melting point | −0.43 °C (31.23 °F; 272.72 K) | ||
| Boiling point | 150.2 °C (302.4 °F; 423.3 K) (decomposes) | ||
| Miscible | |||
| Solubility | soluble in ether, alcohol insoluble in petroleum ether | ||
| log P | -0.43 | ||
| Vapor pressure | 5 mmHg (30 °C) | ||
| Acidity (pKa) | 11.75 | ||
| −17.7·10−6 cm3/mol | |||
Refractive index (nD) | 1.4061 | ||
| Viscosity | 1.245 cP (20 °C) | ||
| 2.26 D | |||
| Thermochemistry | |||
Heat capacity (C) | 1.267 J/(g·K) (gas) 2.619 J/(g·K) (liquid) | ||
Std enthalpy of formation (ΔfH⦵298) | −187.80 kJ/mol | ||
| Pharmacology | |||
| A01AB02 (WHO) D08AX01 (WHO), D11AX25 (WHO), S02AA06 (WHO) | |||
| Hazards | |||
| GHS labelling: | |||
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| Danger | |||
| H271, H302, H314, H332, H335, H412 | |||
| P280, P305+P351+P338, P310 | |||
| NFPA 704 (fire diamond) | |||
| Flash point | Non-flammable | ||
| Lethal dose or concentration (LD, LC): | |||
LD50 (median dose) | 1518 mg/kg[citation needed] 2000 mg/kg (oral, mouse) | ||
LC50 (median concentration) | 1418 ppm (rat, 4 hr) | ||
LCLo (lowest published) | 227 ppm (mouse) | ||
| NIOSH (US health exposure limits): | |||
PEL (Permissible) | TWA 1 ppm (1.4 mg/m3) | ||
REL (Recommended) | TWA 1 ppm (1.4 mg/m3) | ||
IDLH (Immediate danger) | 75 ppm | ||
| Safety data sheet (SDS) | ICSC 0164 (>60% soln.) | ||
| Related compounds | |||
Related compounds | Water Ozone Hydrazine Hydrogen disulfide Dioxygen difluoride | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |||
Hydrogen peroxide is a reactive oxygen species and the simplest peroxide, a compound having an oxygen–oxygen single bond. It decomposes slowly into water and elemental oxygen when exposed to light, and rapidly in the presence of organic or reactive compounds. It is typically stored with a stabilizer in a weakly acidic solution in an opaque bottle. Hydrogen peroxide is found in biological systems including the human body. Enzymes that use or decompose hydrogen peroxide are classified as peroxidases.
hydrogen peroxide (uncountable)
