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Alkynes are hydrocarbons that have at least one triple bond between carbon atoms. The alkynes are traditionally known as acetylenes, though the name acetylene is also used to refer specifically to the simplest member of the series, known officially as ethyne.
1 Physical properties
Unlike an alkane an alkyne is unstable and very reactive. This gives rise to the intense heat of the acetylene flame used in welding.
2 Examples
The simplest alkyne is ethyne ( acetylene):
3 Reactions
- Diels-Alder reaction
- * Pyrone Diels-Alder → aromatic species
- Alkyne-azide reaction → Triazole s
- enediynes (alkyne - alkene - alkyne) → aromatics (Bergman cyclization)
3.1 Terminal alkynes
- terminal alkyne + strong base → anion of terminal alkyne
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- anion of terminal alkyne + ketone → tetrahedral carbonyl addition compound ( alkoxide)
- alkoxide + aqueous acidFor alternative meanings see acid (disambiguation). An acid (represented by the generic formula AH is typically a water-soluble, sour-tasting chemical compound. An acid always has a pH of less than 7. It is a molecule or ion that contains hydrogen or that → hydroxyalkyne
- terminal alkyne + dialkylborane + hydrogen peroxideProperties General Name Hydrogen peroxide Chemical formula H O Appearance Colourless liquid Physical Formula weight 34. 0 amu Melting point 272. 4 °C) Boiling point 423 K (150 °C) Density 1. 4 ×103 kg/ m3 Solubility miscible Thermochemistry ΔH0 -136 → aldehydeAn aldehyde is either a functional group consisting of a terminal carbonyl group, or a compound containing a terminal carbonyl group. Where -R represents the carbon chain. Structure The aldehyde functional group is a carbonyl group bonded to a hydrogen at
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