Puneet Varma

Carbon diselenide

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Formula  CSe2
Molar mass  169.93 g/mol
Appearance  yellow liquid
Boiling point  125.5 °C
Density  2.69 g/cm³
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Carbon diselenide is an inorganic compound with the chemical formula CSe2. It is a yellow-orange oily liquid with pungent odor. It is an analogue of carbon disulfide (CS2). This light-sensitive compound is insoluble in water and soluble in organic solvents.

Contents

Synthesis, structure and reactions

Carbon diselenide is a linear molecule with D∞h symmetry. It is produced by reacting selenium powder with dichloromethane vapor near 550 °C.

2 Se + CH2Cl2 → CSe2 + 2 HCl

It was first reported by Grimm and Metzger, who prepared it by treating hydrogen selenide with carbon tetrachloride in a hot tube.

Like carbon disulfide, carbon diselenide polymerizes under high pressure. The structure of the polymer is thought to be a head-to-head structure with a backbone in the form of –[Se–C(=Se)–C(=Se)–Se]–. The polymer is a semiconductor with a room-temperature conductivity of 50 S/cm.

In addition, carbon diselenide is a precursor to tetraselenafulvalenes, the selenium analogue of tetrathiafulvalene, which can be further used to synthesize organic conductors and organic superconductors.

Carbon diselenide reacts with secondary amines to give dialkydiselenocarbamates:

2 Et2NH + CSe2 → (Et2NH2+)(Et2NCSe2)

Safety

Carbon diselenide has high vapor pressure. It has a moderate toxicity and presents an inhalation hazard. It may be dangerous due to its easy membrane transport. It decomposes slowly in storage (about 1% per month at –30 °C). When obtained commercially, its cost is high.

Mixed with air, carbon diselenide releases an extremely offensive odor. Its smell forced an evacuation of a nearby village when it was first synthesized in 1936. The stench can be neutralized by oxidizing with bleach. Because of the odor, synthetic pathways have been developed to avoid its use.

References

Carbon diselenide Wikipedia


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