Although the small diatomic molecule known as dicarbon or C2 has been known for a long time, its properties and reactivity have really only been determined via its very high temperature generation. My interest started in 2010, when I speculatively proposed here that the related isoelectronic species C⩸N+ might sustain a quadruple bond. Shortly thereafter, a torrent of theoretical articles started to appear in which the idea of a quadruple bond to carbon was either supported or rejected. Clearly more experimental evidence was needed. The recent appearance of a Chemrxiv pre-print entitled “Room-temperature chemical synthesis of C2“.[cite]10.26434/chemrxiv.8009633.v1[/cite] claims to provide just this! Using the synthetic scheme outlined below, they trapped “C2” with a variety of reagents (see Figure 2A in their article), concluding that the observed reactivity best matched that of singlet “biradicaloid” C2 sustaining a quadruple bond.
Archive for May, 2019
Startling bonds: revisiting C⩸N+, via the helium bond in N≡C-He+.
Monday, May 27th, 2019An Ambimodal Trispericyclic Transition State: the effect of solvation?
Thursday, May 2nd, 2019Ken Houk’s group has recently published this study of cycloaddition reactions, using a combination of classical transition state location followed by molecular dynamics trajectory calculations,[cite]10.1021/jacs.8b12674[/cite] and to which Steve Bachrach’s blog alerted me. The reaction struck me as being quite polar (with cyano groups) and so I took a look at the article to see what both the original[cite]10.1021/jo00042a039[/cite] experimental conditions were and how the new simulations compared. The reaction itself is shown below.