RbC2H

Rubidium ethynide (RbC2H) is an inorganic salt composed of rubidium cations and the ethynide anion (C2H−). It belongs to the class of alkali metal acetylides and is typically described as the rubidium salt of the ethynide anion.

Preparation and structure often involve deprotonation of acetylene (HC≡CH) with a strong base such as rubidium amide, or metathesis routes from other rubidium acetylide salts. The solid is usually a white to pale gray, moisture-sensitive material that rapidly hydrolyzes in the presence of water or air, producing acetylene gas and rubidium hydroxide. Consequently, handling requires inert and anhydrous conditions and dry solvents.

Chemical behavior and reactions: RbC2H acts as a strong base and nucleophile. It can be used to generate other acetylide reagents by reaction with electrophiles such as alkyl or aryl halides, enabling the formation of substituted alkynes after workup. It also serves as a source of the ethynide moiety in various synthetic sequences. On hydrolysis, it releases acetylene gas, illustrating its sensitivity to moisture.

Applications and use: In inorganic and organometallic synthesis, rubidium acetylides are employed to introduce ethynyl groups into molecules. They are less common than lithium or sodium analogs but are used when a specific reactivity profile is advantageous.

Safety and storage: RbC2H is highly reactive and both air- and moisture-sensitive. It should be stored under inert atmosphere and handled with dry, aprotic solvents. Contact with water or oxygen evolves acetylene and can be hazardous; appropriate precautions are required. See also related alkali metal acetylides such as NaC2H and CsC2H.