Chemists report longest C–C bond

Abstract

The single carbon-carbon bond is among the most familiar covalent connections in organic compounds. But a new study suggests that chemists have yet to fully explore the limits of this basic bond. Scientists have previously found that these ubiquitous bonds, which typically measure about 1.54 Å in length, can be elongated through the use of bulky substituents to endow molecules with special properties. Now, researchers led by Takanori Suzuki and Yusuke Ishigaki at Hokkaido University have synthesized a molecule with the longest reported C–C bond, measuring 1.806 Å in length (Chem 2018, DOI: 10.1016/j.chempr.2018.01.011). The team set out to break the record by designing a stable dihydropyracylene compound with a highly strained core and two spirocyclic units that are forced to face each other, helping stretch out the central carbon-carbon bond. The chemists confirmed the presence of the C–C bond by observing its stretching vibration through Raman spectroscopy, and they