The Willgerodt reaction[cite]10.1002/cber.18870200278[/cite], discovered in 1887 and shown below, represents a transformation with a once famously obscure mechanism. A major step in the elucidation of that mechanism came[cite]10.1021/ja01157a034[/cite] using the then new technique of 14 C radio-labelling, shortly after the atom bomb projects during WWII made 14 CO 2 readily available to researchers.
One of the most fascinating and important articles dealing with curly arrows I have seen is that by Klein and Knizia on the topic of C-H bond activations using an iron catalyst.[cite]10.1002/anie.201805511[/cite] These are so-called high spin systems with unpaired electrons and the mechanism of C-H activation involves both double headed (two electron) and fish-hook (single electron) movement.
Metaldehyde is an insecticide used to control slugs. When we unsuccessfully tried to get some recently, I discovered it is now deprecated in the UK. So my immediate reaction was to look up its structure to see if that cast any light (below, R=CH3, shown as one stereoisomer).
With the current global lockdown, and students along with everyone else staying at home, I have noticed some old posts of mine are getting more attention than normal.
My previous two posts on the topic of strongest bonds have involved mono and diprotonating N 2 and using quantum mechanics to predict the effect this has on the N-N bond via its length and vibrational stetching mode. Such species are very unlikely to be easily observed for verification.
I occasionally notice that posts that first appeared here many years ago suddenly attract attention.
Earlier, I explored the choreography or “timing”, of what might be described as the curly arrows for a typical taught reaction mechanism, the 1,4-addition of a nucleophile to an unsaturated carbonyl compound (scheme 1). I am now going to explore the consequences of changing one of the actors by adding the nucleophile to an unsaturated imine rather than carbonyl compound (scheme 2).
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 a previous post, I talked about a library of reaction pathway intrinsic reaction coordinates (IRCs) containing 115 examples of organic and organometallic reactions. Now (thanks Dean!) I have been alerted to a brand new databank of dynamics trajectories (DDT), with the focus on those reactions taught in undergraduate organic chemistry courses, some of which are shown below.
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.
A reaction can be thought of as molecular dancers performing moves. A choreographer is needed to organise the performance into the ballet that is a reaction mechanism. Here I explore another facet of the Michael addition of a nucleophile to a conjugated carbonyl compound.
