 | |||
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| Names | |||
|---|---|---|---|
| IUPAC name Hydrogen selenide | |||
| Other names Hydroselenic acid selane selenium hydride | |||
| Identifiers | |||
3D model (JSmol) | |||
| ChEBI | |||
| ChemSpider |
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| ECHA InfoCard | 100.029.071 | ||
| EC Number |
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| KEGG |
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| RTECS number |
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| UNII | |||
| UN number | 2202 | ||
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| Properties | |||
| H2Se | |||
| Molar mass | 80.98 g/mol | ||
| Appearance | Colorless gas | ||
| Odor | decayedhorseradish[1] | ||
| Density | 3.553 g/dm3 | ||
| Melting point | −65.73 °C (−86.31 °F; 207.42 K) | ||
| Boiling point | −41.25 °C (−42.25 °F; 231.90 K) | ||
| 0.70 g/100 mL | |||
| Solubility | soluble inCS2,phosgene | ||
| Vapor pressure | 9.5 atm (21°C)[1] | ||
| Acidity (pKa) | 3.89 | ||
| Conjugate acid | Selenonium | ||
| Conjugate base | Selenide | ||
| Structure | |||
| Bent | |||
| Hazards | |||
| Occupational safety and health (OHS/OSH): | |||
Main hazards | Extremely toxic and flammable | ||
| GHS labelling: | |||
   | |||
| Danger | |||
| H220,H330,H410 | |||
| P210,P260,P271,P273,P284,P304+P340,P310,P320,P377,P381,P391,P403,P403+P233,P405,P410+P403,P501 | |||
| NFPA 704 (fire diamond) | |||
| Flash point | flammable gas | ||
| Lethal dose or concentration (LD, LC): | |||
LCLo (lowest published) | 0.3 ppm (guinea pig, 8 hr) 5.9 ppm (rat, 1 hr)[2] | ||
| NIOSH (US health exposure limits): | |||
PEL (Permissible) | TWA 0.05 ppm (0.2 mg/m3)[1] | ||
REL (Recommended) | TWA 0.05 ppm (0.2 mg/m3)[1] | ||
IDLH (Immediate danger) | 1 ppm[1] | ||
| Safety data sheet (SDS) | ICSC 0284 | ||
| Related compounds | |||
Otheranions | H2O H2S H2Te H2Po | ||
Othercations | Na2Se Ag2Se | ||
Related compounds | Arsine | ||
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Hydrogen selenide is aninorganic compound with the formula H2Se. Thishydrogen chalcogenide is the simplest and most commonly encounteredhydride ofselenium. H2Se is a colorless, flammable gas under standard conditions. It isthe most toxic selenium compound[3] with an exposure limit of 0.05ppm over an 8-hour period.[4][5] Even at extremely low concentrations, this compound has a very irritating smell resembling that of decayed horseradish or "leaking gas", but smells of rotten eggs at higher concentrations.
H2Se adopts abent structure with a H−Se−H bond angle of 91°[citation needed]. Consistent with this structure, threeIR-active vibrational bands are observed: 2358, 2345, and 1034 cm−1.[6]
The properties ofH2S and H2Se are similar, although the selenide is more acidic with pKa = 3.89 and the second pKa = 11,[6] or 15.05 ± 0.02 at 25 °C.[7]
Industrially, it is produced by treatingelemental selenium at T > 300 °C with hydrogen gas.[8] A number of routes to H2Se have been reported, which are suitable for both large and small scale preparations. In the laboratory, H2Se is usually prepared by the action of water onAl2Se3, concomitant with formation of hydratedalumina. A related reaction involves the acid hydrolysis of FeSe.[9]
H2Se can also be prepared by means of different methods based on thein situ generation in aqueous solution usingboron hydride,Marsh test andDevarda's alloy. According to the Sonoda method, H2Se is generated from the reaction of H2O and CO on Se in the presence ofEt3N.[10] H2Se can be purchased in cylinders.
Elemental selenium can be recovered from H2Se through a reaction with aqueoussulfur dioxide (SO2).
Its decomposition is used to prepare the highly pure element.
H2Se is commonly used in the synthesis of Se-containing compounds. It adds across alkenes. Illustrative is the synthesis ofselenoureas fromcyanamides:[11]
H2Se gas is used todope semiconductors with selenium.
Hydrogen selenide is hazardous, being the most toxic selenium compound[3] and far more toxic than itscongenerhydrogen sulfide. Thethreshold limit value is 0.05 ppm. The gas acts as an irritant at concentrations higher than 0.3 ppm, which is the main warning sign of exposure; below 1 ppm, this is "insufficient to prevent exposure", while at 1.5 ppm the irritation is "intolerable".[5] Exposure at high concentrations, even for less than a minute, causes the gas to attack the eyes and mucous membranes; this causes cold-like symptoms for at least a few days afterwards. In Germany, the limit in drinking water is 0.008 mg/L, and the US EPA recommends a maximum contamination of 0.01 mg/L.[8][12]
Despite being extremely toxic, no human fatalities have yet been reported. It is suspected that this is due to the gas' tendency to oxidise to form red selenium in mucous membranes; elemental selenium is less toxic than selenides are.[4]
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