Sometimes a (scientific) thought just pops into one’s mind. Most are probably best not shared with anyone, but since its the summer silly season, I thought I might with this one. Famously, according to Einstein, m  = E/c^^2, the equivalence of energy to mass. Consider a typical exoenergic chemical reaction:  A → B, ΔG -100 kJ/mol.

Metaldehyde is an insecticide used to control slugs.

I occasionally notice that posts that first appeared here many years ago suddenly attract attention.

A little more than a year ago, a ChemRxiv pre-print appeared bearing the title referenced in this post,[cite]10.26434/chemrxiv.8009633.v1[/cite] which immediately piqued my curiosity. The report presented persuasive evidence, in the form of trapping experiments, that dicarbon or C ₂ had been formed by the following chemical synthesis.

In the news this week is a report of a molecule whose crystal lattice is capable of both storing and releasing large amounts of hydrogen gas at modest pressures and temperatures. Thus “NU-1501-Al” can absorb 14 weight% of hydrogen. To power a low-polluting car with a 500 km range, about 4-5 kg of hydrogen gas would be need to be stored and released safely.

In 2001, Shaik and co-workers published the first of several famous review articles on the topic A Different Story of π-Delocalization.

In a welcome move, one of the American chemical society journals has published an encouragement to submit what is called FAIR data to the journal.[cite]10.1021/acs.orglett.0c00383[/cite]. A reminder that FAIR data is data that can be Found (F), Accessed (A), Interoperated(I) and Re-used( R). I thought I might try to explore this new tool here. You start at the ACS Research Data Center

I noted in an earlier blog, a potential (if difficult) experimental test of the properties of the singlet state of dicarbon, C ₂ . Now, just a few days ago, a ChemRxiv article has been published suggesting another (probably much more realistic) test.[cite]10.26434/chemrxiv.11446224.v1[/cite] This looks at the so-called ⁷ Σ open shell state of the molecule where three electrons from one σ and two π orbitals are excited

Having shown that carbon as a carbene centre, C : can act as a hydrogen bond acceptor, as seen from a search of crystal structures, I began to wonder if there is any chance that carbon as a radical centre, C• could do so as well. Definitely a subversive thought, since radical centres are supposed to abstract hydrogens rather than to hydrogen bond to them.

In the previous post, I showed that carbon can act as a hydrogen bond acceptor (of a proton) to form strong hydrogen bond complexes. Which brings me to a conceptual connection: can singlet dicarbon form such a hydrogen bond?  Dicarbon can be variously represented as above. The first form shows it as a bis-carbene, with an unbonded lone pair of electrons at each end of a carbon double bond.