Derek Lowe tells the story of “carbyne”, a potential further allotrope of carbon, comprising linear chains of carbon atoms, C-C≡C-C≡C-C. Whether such a molecule can exist on its own has long been the the topic of speculation.
This is another in the C&E News list of candidates for the Molecule of the Year, Molecular shuttle in a box [cite]10.1002/anie.202318829[/cite] Mirror-image cyclodextrin [cite]10.1038/s44160-024-00495-8[/cite] Molecular shuttle in a box [cite]10.1002/anie.202318829[/cite] Rule-bending strained alkene [cite]10.1126/science.adq3519[/cite] First soluble promethium complex [cite]10.1038/s41586-024-07267-6[/cite]
Each year C&E News publishes a list of candidates for the Molecule of the Year.
The idea of so-called FAIR (Findable, Accessible, Interoperable and Reusable) data is that each object has an associated metadata record which serves to enable the four aspects of FAIR. Each such record is itself identified by a persistent identifier known as a DOI.
With AI and Machine learning needing data in abundance, interest in data discovery is intense. However, this type of discovery is somewhat different from more traditional data base searches, in that it is particularly suited for machine discovery as well as by humans. The discovery searches are conducted using an aggregated and federated metadata store, such as that curated by DataCite.
Michael in a comment here on the mechanism of the Masamune-Bergman reaction notes that when it occurs as part of the Calicheamicin (an antibody-drug conjugate or ADC) version of this mechanism, a pre-step is first necessary. As discussed in this review article,[cite]10.3390/ph14050442[/cite] the trisulfide linkage is reduced and the resulting thiolate undergoes a facile 1,4-addition to the adjacent enone.
In exploring one-electron carbon-carbon bonds, I had noted previously[cite]10.59350/88k04-2×509[/cite] that both hexafluoroethane and ethane itself could each lose an electron to produce such species. A discussion developed in which a molecule isoelectronic with ethane, namely the methyl-λ1-borane radical (H 3 B-CH 3 ) was proposed by Jacob.
In the previous post, I looked[cite]10.59350/xp5a3-zsa24[/cite] at the recently reported[cite]10.1021/ja02261a002[/cite] hexa-arylethane containing a carbon-carbon one-electron bond, its structure having been determined by x-ray diffraction (XRD). The measured C-C bond length was ~2.9aÅ and my conclusion was that the C…C region represented more of a weak “interaction” than of a bond as such. How about a much simpler system,
More than 100 years ago, before the quantum mechanical treatment of molecules had been formulated, G. N. Lewis proposed[cite]10.1021/ja02261a002[/cite] a simple model for chemical bonding that is still taught today. This is the idea of the three categories of bond we know as single, double and triple, comprising respectively two, four and six shared electrons each, at least for the very common carbon-carbon bond.
Calicheamicin was noted in the previous post as a natural product with antitumour properties and having many weird structural features such as an unusual “enedidyne” motif. The representation is shown below. A partial structure shown below for Calicheamicin replaces the -(CH 2 )4- substructure with a four carbon chain that includes two sp 2 centres instead of two sp 3 centres.
