Overview
Hydrogen selenide is a chemical compound with the formula H2Se. It is the simplest hydrogen selenide and the selenium analogue of hydrogen sulfide. In its pure form it is a colorless gas with a very unpleasant odor and notable toxicity. When dissolved in water it is often referred to as hydroselenic acid.
Properties and structure
H2Se is a small, bent molecule with two hydrogen atoms bonded to a central selenium atom. It behaves as a weak binary acid in aqueous solution and can donate one or two protons to give selenide species. The gas is heavier than air and is chemically reducing; it reacts readily with oxidizing agents and can be decomposed to yield elemental selenium.
Preparation and reactions
In the laboratory hydrogen selenide is commonly generated by treating metal selenides with strong acids or by the controlled reduction of selenium compounds. For industrial and research guidance on preparation and handling, consult technical sources such as safety data sheets or specialist chemistry references (general reference). H2Se undergoes oxidation to selenium oxides and reacts with metal ions to form selenides.
Uses and applications
Although use is limited by its toxicity, hydrogen selenide is an important reagent for producing metal selenide compounds used in semiconductor and photovoltaic materials. It is also employed in specialized organic and inorganic syntheses where introduction of selenium is required. For application notes and material data consult dedicated industry resources (applications).
Safety and environmental effects
H2Se is acutely toxic by inhalation; exposures can cause severe respiratory injury and may be fatal. It is handled only in well-ventilated fume hoods with gas detection and strict controls. Environmental release should be avoided because of toxicity to wildlife; emergency and exposure guidelines are provided by occupational and environmental agencies (safety guidance).
Distinctions and notable facts
Hydrogen selenide is often compared to hydrogen sulfide: both share similar chemistry but differ in reactivity and toxicity. H2Se is generally considered more hazardous and more readily oxidized to selenium-containing compounds. For further chemical and regulatory detail see specialized chemical databases and review articles (further reading).