Ethynyl group

Overview of the ethynyl group in organic chemistry

Ethynyl group
Ethynyl-group-2D-skeletal.png
Skeletal structure of the ethynyl group
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ChEMBL
Properties
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GHS Pictograms	[[File:|50px]]
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References

The ethynyl group is a functional group in organic chemistry consisting of a carbon-carbon triple bond with the formula −C≡CH. It is derived from acetylene (C₂H₂) by the removal of one hydrogen atom. The ethynyl group is a key structural motif in many organic compounds and is known for its linear geometry and high reactivity.

Structure and Bonding

The ethynyl group is characterized by a carbon-carbon triple bond, which consists of one sigma (σ) bond and two pi (π) bonds. The carbon atoms in the ethynyl group are sp-hybridized, resulting in a linear geometry with a bond angle of 180°.

Reactivity

The ethynyl group is highly reactive due to the presence of the triple bond. It can participate in a variety of chemical reactions, including:

• Nucleophilic addition: The triple bond can act as a nucleophile, reacting with electrophiles to form new carbon-carbon or carbon-heteroatom bonds.
• Hydrogenation: The ethynyl group can be hydrogenated to form alkenes or alkanes, depending on the conditions and catalysts used.
• Halogenation: The triple bond can react with halogens to form dihaloalkenes or tetrahaloalkanes.
• Metal-catalyzed coupling reactions: The ethynyl group can undergo coupling reactions such as the Sonogashira coupling to form carbon-carbon bonds with aryl or vinyl halides.

Applications

The ethynyl group is found in a wide range of natural and synthetic compounds. It is a key component in pharmaceuticals, agrochemicals, and materials science. Some notable applications include:

• Pharmaceuticals: Ethynyl groups are present in drugs such as ethynylestradiol, a synthetic estrogen used in oral contraceptives.
• Materials science: Ethynyl groups are used in the synthesis of polymers and advanced materials, such as polyacetylene and carbon nanotubes.

Safety and Handling

Compounds containing ethynyl groups can be hazardous due to their reactivity and potential to form explosive mixtures with air. Proper safety precautions, including the use of appropriate personal protective equipment and ventilation, should be observed when handling these compounds.

Also see

• Alkyne
• Acetylene
• Sonogashira coupling
• Carbon-carbon bond