 | |||
| |||
| Names | |||
|---|---|---|---|
| IUPAC names Arsenic trihydride Arsane Trihydridoarsenic | |||
| Other names Arseniuretted hydrogen, Arsenous hydride, Hydrogen arsenide Arsenic hydride | |||
| Identifiers | |||
3D model (JSmol) | |||
| ChEBI | |||
| ChEMBL | |||
| ChemSpider |
| ||
| ECHA InfoCard | 100.029.151 | ||
| EC Number |
| ||
| 599 | |||
| KEGG | |||
| RTECS number |
| ||
| UNII | |||
| UN number | 2188 | ||
| |||
| |||
| Properties | |||
| AsH3 | |||
| Molar mass | 77.9454 g/mol | ||
| Appearance | Colourless gas | ||
| Odor | Faint, garlic-like | ||
| Density | 4.93 g/L, gas; 1.640 g/mL (−64 °C) | ||
| Melting point | −111.2 °C (−168.2 °F; 162.0 K) | ||
| Boiling point | −62.5 °C (−80.5 °F; 210.7 K) | ||
| 0.2 g/100 mL (20 °C)[1] 0.07 g/100 mL (25 °C) | |||
| Solubility | soluble inchloroform,benzene | ||
| Vapor pressure | 14.9 atm[1] | ||
| Conjugate acid | Arsonium | ||
| Structure | |||
| Trigonal pyramidal | |||
| 0.20 D | |||
| Thermochemistry | |||
Std molar entropy(S⦵298) | 223 J⋅K−1⋅mol−1 | ||
Std enthalpy of formation(ΔfH⦵298) | +66.4 kJ/mol | ||
| Hazards | |||
| Occupational safety and health (OHS/OSH): | |||
Main hazards | Extremely toxic, explosive, flammable, potential occupational carcinogen[1] | ||
| GHS labelling: | |||
    | |||
| Danger | |||
| H220,H330,H373,H410 | |||
| P210,P260,P271,P273,P284,P304+P340,P310,P314,P320,P377,P381,P391,P403,P403+P233,P405,P501 | |||
| NFPA 704 (fire diamond) | |||
| Flash point | −62 °C (−80 °F; 211 K) | ||
| Explosive limits | 5.1–78%[1] | ||
| Lethal dose or concentration (LD, LC): | |||
LD50 (median dose) | 2.5 mg/kg (intravenous)[2] | ||
LC50 (median concentration) |
| ||
LCLo (lowest published) |
| ||
| NIOSH (US health exposure limits): | |||
PEL (Permissible) | TWA 0.05 ppm (0.2 mg/m3)[1] | ||
REL (Recommended) | C 0.002 mg/m3 [15-minute][1] | ||
IDLH (Immediate danger) | 3 ppm[1] | ||
| Related compounds | |||
Relatedhydrides | Ammonia Phosphine Stibine Bismuthine | ||
Related compounds | Hydrogen selenide | ||
| Supplementary data page | |||
| Arsine (data page) | |||
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Arsine (IUPAC name:arsane) is aninorganic compound with theformulaAsH3. This flammable,pyrophoric, and highly toxicpnictogen hydride gas is one of the simplest compounds ofarsenic.[4] Despite its lethality, it finds some applications in the semiconductor industry and for the synthesis of organoarsenic compounds. The termarsine is commonly used to describe a class oforganoarsenic compounds of the formula AsH3−xRx, where R =aryl oralkyl. For example, As(C6H5)3, calledtriphenylarsine, is referred to as "an arsine".
In its standard state arsine is a colorless, denser-than-air gas that is slightly soluble inwater (2% at 20 °C)[1] and in manyorganic solvents as well.[5] Arsine itself is odorless,[6] but it oxidizes in air and this creates a slightgarlic or fish-like scent when the compound is present above 0.5 ppm.[7] This compound is kinetically stable: at room temperature it decomposes only slowly. At temperatures of ca. 230 °C, decomposition to arsenic and hydrogen is sufficiently rapid to be the basis of theMarsh test for arsenic presence. Similar tostibine, the decomposition of arsine is autocatalytic, as the arsenic freed during the reaction acts as a catalyst for the same reaction.[8] Several other factors, such ashumidity, presence of light and certaincatalysts (namelyalumina) facilitate the rate of decomposition.[9]
AsH3 is atrigonal pyramidal molecule with H–As–H angles of 91.8° and three equivalent As–H bonds, each of 1.519Å length.[10]
AsH3 is generally prepared by the reaction of As3+ sources with H− equivalents.[11]
As reported in 1775,Carl Scheele reducedarsenic(III) oxide with zinc in the presence of acid.[12] This reaction is a prelude to theMarsh test.
Alternatively, sources of As3− react with protonic reagents to also produce this gas. Zinc arsenide andsodium arsenide are suitable precursors:[13]
The understanding of the chemical properties of AsH3 is well developed and can be anticipated based on an average of the behavior ofpnictogen counterparts, such asPH3 andSbH3.
Typical for a heavy hydride (e.g.,SbH3,H2Te,SnH4),AsH3 is unstable with respect to its elements. In other words, it is stable kinetically but not thermodynamically.
This decomposition reaction is the basis of the Marsh test, which detects elemental As.
Continuing the analogy to SbH3, AsH3 is readilyoxidized by concentrated O2 or the dilute O2 concentration in air:
Arsine will react violently in presence of strong oxidizing agents, such aspotassium permanganate,sodium hypochlorite, ornitric acid.[9]
AsH3 is used as a precursor to metal complexes of "naked" (or "nearly naked") arsenic. An example is the dimanganese species [(C5H5)Mn(CO)2]2AsH, wherein the Mn2AsH core is planar.[14]
A characteristic test for arsenic involves the reaction of AsH3 with Ag+, called the Gutzeit test for arsenic.[15] Although this test has become obsolete inanalytical chemistry, the underlying reactions further illustrate the affinity of AsH3 for "soft" metal cations. In the Gutzeit test, AsH3 is generated by reduction of aqueous arsenic compounds, typicallyarsenites, with Zn in the presence of H2SO4. The evolved gaseous AsH3 is then exposed to AgNO3 either as powder or as a solution. With solid AgNO3, AsH3 reacts to produce yellow Ag4AsNO3, whereas AsH3 reacts with a solution of AgNO3 to give black Ag3As.
The acidic properties of the As–H bond are often exploited. Thus, AsH3 can be deprotonated:
Upon reaction with the aluminium trialkyls, AsH3 gives the trimeric [R2AlAsH2]3, where R = (CH3)3C.[16] This reaction is relevant to the mechanism by which GaAs forms from AsH3 (see below).
AsH3 is generally considered non-basic, but it can be protonated bysuperacids to give isolable salts of the tetrahedral species [AsH4]+.[17]
Reactions of arsine with thehalogens (fluorine andchlorine) or some of their compounds, such asnitrogen trichloride, are extremely dangerous and can result in explosions.[9]
In contrast to the behavior of PH3, AsH3 does not form stable chains, although diarsine (or diarsane) H2As–AsH2, and even triarsane H2As–As(H)–AsH2 have been detected. The diarsine is unstable above −100 °C.
AsH3 is used in the synthesis of semiconducting materials related tomicroelectronics andsolid-state lasers. Related tophosphorus, arsenic is ann-dopant for silicon and germanium.[9] More importantly, AsH3 is used to make thesemiconductorGaAs bychemical vapor deposition (CVD) at 700–900 °C:
For microelectronic applications, arsine can be provided by a sub-atmospheric gas source (a source that supplies less than atmospheric pressure). In this type of gas package, the arsine is adsorbed on a solid microporous adsorbent inside a gas cylinder. This method allows the gas to be stored without pressure, significantly reducing the risk of an arsine gas leak from the cylinder. With this apparatus, arsine is obtained by applying vacuum to the gas cylinder valve outlet. Forsemiconductor manufacturing, this method is feasible, as processes such as ion implantation operate under high vacuum.
Since beforeWWII AsH3 was proposed as a possiblechemical warfare weapon. The gas is colorless, almost odorless, and 2.5 times denser than air, as required for a blanketing effect sought in chemical warfare. It is also lethal in concentrations far lower than those required to smell itsgarlic-like scent. In spite of these characteristics, arsine was never officially used as a weapon, because of its high flammability and its lower efficacy when compared to the non-flammable alternativephosgene. On the other hand, severalorganic compounds based on arsine, such aslewisite (β-chlorovinyldichloroarsine),adamsite (diphenylaminechloroarsine),Clark 1 (diphenylchloroarsine) and Clark 2 (diphenylcyanoarsine) have been effectively developed for use in chemical warfare.[18]
AsH3 is well known inforensic science because it is a chemical intermediate in the detection of arsenic poisoning. The old (but extremely sensitive)Marsh test generates AsH3 in the presence of arsenic.[4] This procedure, published in 1836 byJames Marsh,[19] is based upon treating an As-containing sample of a victim's body (typically the stomach contents) with As-freezinc and dilutesulfuric acid: if the sample contains arsenic, gaseous arsine will form. The gas is swept into a glass tube and decomposed by means of heating around 250–300 °C. The presence of As is indicated by formation of a deposit in the heated part of the equipment. On the other hand, the appearance of a black mirror deposit in thecool part of the equipment indicates the presence of antimony (the highly unstableSbH3 decomposes even at low temperatures).
The Marsh test was widely used by the end of the 19th century and the start of the 20th; nowadays more sophisticated techniques such asatomic spectroscopy,inductively coupled plasma, andx-ray fluorescence analysis are employed in the forensic field. Thoughneutron activation analysis was used to detect trace levels of arsenic in the mid 20th century, it has since fallen out of use in modern forensics.
The toxicity of arsine is distinct from that of other arsenic compounds. The main route of exposure is by inhalation, although poisoning after skin contact has also been described. Arsine attackshemoglobin in thered blood cells, causing them to be destroyed by the body.[20][21]
The first signs of exposure, which can take several hours to become apparent, areheadaches,vertigo, andnausea, followed by the symptoms ofhaemolytic anaemia (high levels of unconjugatedbilirubin),haemoglobinuria andnephropathy. In severe cases, the damage to thekidneys can be long-lasting.[1]
Exposure to arsine concentrations of 250 ppm is rapidly fatal: concentrations of 25–30 ppm are fatal for 30 min exposure, and concentrations of 10 ppm can be fatal at longer exposure times.[3] Symptoms of poisoning appear after exposure to concentrations of 0.5 ppm. There is little information on the chronic toxicity of arsine, although it is reasonable to assume that, in common with other arsenic compounds, a long-term exposure could lead toarsenicosis.[citation needed]
Arsine is a potent hemolytic agent, which is in line with its pathophysiological course of action. However, inhaling high concentrations of this agent is highly capable of inducing severe and direct pulmonary trauma. From a strictly clinical perspective, this typically manifests as chemical pneumonitis as well as non-cardiogenic pulmonary edema.[22] Generally, pathological examinations of the acute fatal cases of arsine poisoning have positively identified two primary mechanisms of pulmonary injury:
Both manifestations are capable of leading to respiratory failure and death, often occurring at the same time as acute renal failure caused by hemolytic injury.[24]
It is classified as anextremely hazardous substance in the United States as defined in Section 302 of the U.S.Emergency Planning and Community Right-to-Know Act (42 U.S.C. 11002), and is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities.[25]
| Country | Limit[26] |
|---|---|
| Argentina | TLV-TWA0.005 ppm |
| Australia | TWA0.05 ppm (0.16 mg/m3) |
| Austria |
|
| Belgium | TWA0.05 ppm (0.16 mg/m3) |
| Bulgaria | TLV-TWA0.005 ppm |
| British Columbia, Canada | TLV-TWA0.005 ppm |
| Colombia | TLV-TWA0.005 ppm |
| Denmark | TWA0.01 ppm (0.03 mg/m3) |
| Egypt | TWA0.05 ppm (0.2 mg/m3) |
| Finland | TWA0.01 mg(As)/m3 |
| France | |
| Hungary |
|
| Japan |
|
| Jordan | TLV-TWA0.005 ppm |
| Mexico | TWA0.05 ppm (0.2 mg/m3) |
| Netherlands | MAC-TCG0.2 mg/m3 |
| New Zealand |
|
| Norway | TWA0.003 ppm (0.01 mg/m3) |
| Peru | TWA0.05 ppm (0.16 mg/m3) |
| Philippines | 0.05 ppm (0.5 mg/m3) |
| Poland |
|
| Russia | STEL (0.1 mg/m3) |
| Singapore | TLV-TWA0.005 ppm |
| South Korea | TWA0.2 mg(As)/m3 |
| Sweden | TWA0.02 ppm (0.05 mg/m3) |
| Switzerland | MAK-week0.05 ppm (0.16 mg/m3) |
| Thailand | TWA0.05 ppm (0.2 mg/m3) |
| Turkey | TWA0.05 ppm (0.2 mg/m3) |
| United Kingdom | TWA0.05 ppm (0.16 mg/m3) |
| United States | |
| Vietnam | TLV-TWA0.005 ppm |
While arsine itself is odourless, its oxidation by air may produce a slight, garlic-like scent. However, it is lethal in concentrations far lower than those required to produce this smell.
