Polyyne
Organic chains of alternating single and triple bonds.
Polyynes are organic compounds characterized by alternating single and triple bonds, forming a series of consecutive alkynes (−C≡C−)n with n greater than 1. Also called polyacetylenes or oligoynes, they are distinguished by their rigidity and high conductivity, making them promising as molecular wires in nanotechnology.
- first_synthesizer
- Carl Andreas Glaser
- field
- Organic chemistry, materials science, astrochemistry
- known_for
- Alternating single and triple bonds; high conductivity; molecular wires; interstellar detection
- longest_isolated_chain
- 22 acetylenic units (44 carbon atoms) as of 2010
Lore & Background
Interest in these compounds has stimulated research into their preparation by organic synthesis, using methods such as Glaser coupling, Hay protocols, Cadiot–Chodkiewicz coupling, and the Fritsch–Buttenberg–Wiechell rearrangement. During the 1950s, polyynes H(−C≡C−)nH with n up to 4 or 5 were synthesized. R. Johnson and D. R. M. Walton developed end-caps of the form –SiR3 to protect the polyyne chain, obtaining chains with n up to 8 in pure state and n up to 16 in solution. Later, Tykwinski and co-workers obtained chains up to C20, and in 2002 a polyyne with 10 acetylenic units was isolated. The longest polyyne isolated as of 2010 had 22 acetylenic units (44 carbon atoms), end-capped with tris(3,5-di-t-butylphenyl)methyl groups.
Reader's Guide
Polyynes are significant for their unique electronic properties, including high conductivity and rigidity, which position them as candidates for molecular-scale wires in nanotechnology. Their synthesis has driven the development of multiple coupling reactions, and their stability challenges have led to innovative end-capping strategies using bulky groups. In nature, polyynes are produced by a wide range of organisms, including plants such as carrot, celery, and giant ragweed, where they exhibit biological activities like cytotoxicity, antibiotic, antiviral, and nematocidal effects. They have also been detected in interstellar molecular clouds. However, long polyyne chains are inherently unstable in bulk due to exothermic cross-linking, and explosions are a real hazard in research. Disputes exist regarding claims of synthesizing 'carbyne' (−C≡C−)∞, with some early identifications now considered short polyyne chains. The legacy of polyynes lies at the intersection of synthetic chemistry, materials science, astrochemistry, and natural products chemistry.
Did You Know?
- The simplest polyyne is diacetylene or butadiyne, H−C≡C−C≡C−H.
- Polyynes have been detected in interstellar molecular clouds where hydrogen is scarce.
- The longest polyyne isolated as of 2010 had 22 acetylenic units (44 carbon atoms).
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