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Alkynes

CₙH₂ₙ₋₂ (acyclic); R-C≡C-R' (general)
Quick Reference
Formula / NotationCₙH₂ₙ₋₂ (acyclic); R-C≡C-R' (general)
Also Known AsAlkynes; alkyne hydrocarbons; acetylenic compounds; CₙH₂ₙ₋₂ series; ethyne (acetylene)

What is Alkynes?

Alkynes are unsaturated hydrocarbons containing at least one carbon–carbon triple bond (C≡C). The general formula for acyclic alkynes is CₙH₂ₙ₋₂. The simplest alkyne is ethyne (acetylene, HC≡CH). Alkynes are more reactive than alkenes and alkanes due to the triple bond. Terminal alkynes (with ≡C–H) are weakly acidic.

Formula & Notation

CₙH₂ₙ₋₂ (acyclic); R-C≡C-R' (general)

Other Names / Synonyms: Alkynes; alkyne hydrocarbons; acetylenic compounds; CₙH₂ₙ₋₂ series; ethyne (acetylene)

Properties & Characteristics

General formula CₙH₂ₙ₋₂; contain C≡C triple bond (one σ + two π bonds); linear geometry around triple bond; terminal alkynes are weakly acidic (pKa ~25, can form acetylide salts); undergo addition reactions and electrophilic addition; lower alkynes are gases

Uses & Applications

Acetylene (ethyne) for oxy-acetylene welding and cutting; chemical synthesis starting materials; organic synthesis (Sonogashira coupling, Glaser coupling); polymerisation to polyacetylene (conducting polymer); synthesis of aldehydes, ketones, and other intermediates

Safety Information

Acetylene is highly flammable and can form explosive mixtures with air. Acetylene cylinders must never be laid on their side. Metal acetylides (copper, silver) formed in impure systems are shock-sensitive explosives. Terminal alkynes are mildly acidic and may irritate skin.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Alkynes
Formula CₙH₂ₙ₋₂ (acyclic); R-C≡C-R' (general)
Synonyms Alkynes; alkyne hydrocarbons; acetylenic compounds; CₙH₂ₙ₋₂ series; ethyne (acetylene)

Frequently Asked Questions

Alkynes are unsaturated hydrocarbons containing at least one carbon–carbon triple bond (C≡C). The general formula for acyclic alkynes is CₙH₂ₙ₋₂. The simplest alkyne is ethyne (acetylene, HC≡CH). Alkynes are more reactive than alkenes and alkanes due to the triple bond. Terminal alkynes (with ≡C–H) are weakly acidic.

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