This is a spin-off from the table I constructed here for further chemical examples of the classical/non-classical norbornyl cation conundrum. One possible entry would include the transition state for inversion of methane via a square planar geometry as compared with e.g. NiH 4 for which the square planar motif is its minimum.
The story so far. Inspired by the report of the most polar neutral compound yet made, I suggested some candidates based on the azulene ring system that if made might be even more polar. This then led to considering a smaller π-analogue of azulene, m-benzyne. Here I ponder how a derivative of this molecule might be made, using computational profiling as one reality check.
Is asking a question such as “what is the smallest angle subtended at a chain of three connected 4-coordinate carbon atoms” just seeking another chemical record, or could it unearth interesting chemistry?
Previously, a mechanistic twist to the oxidation of imines using peracid had emerged. Time to see how substituents respond to this mechanism. With X = NO 2 100% oxaziridine and no nitrone is obtained experimentally;
The story so far. Imines react with a peracid to form either a nitrone (σ-nucleophile) or an oxaziridine (π-nucleophile).[cite]10.1016/S0040-4039(00)98582-4[/cite] The balance between the two is on an experimental knife-edge, being strongly influenced by substituents on the imine.
Nucleophiles are species that seek to react with an electron deficient centre by donating a lone or a π-bond pair of electrons. The ambident variety has two or more such possible sources in the same molecule, an example of which might be hydroxylamine or H 2 NOH.
Bromoallene is a pretty simple molecule, with two non-equivalent double bonds. How might it react with an electrophile, say dimethyldioxirane (DMDO) to form an epoxide?[cite]10.1039/C6CC06395K[/cite] Here I explore the difference between two different and very simple approaches to predicting its reactivity. Both approaches rely on the properties of the reactant and use two types of molecule orbitals derived from its electronic wavefunction.
In the previous post, I explored the mechanism for nucleophilic substitution at a silicon centre proceeding via retention of configuration involving a Berry-like pseudorotation. Here I probe an alternative route involving inversion of configuration at the Si centre.
The substitution of a nucleofuge (a good leaving group) by a nucleophile at a carbon centre occurs with inversion of configuration at the carbon, the mechanism being known by the term S N 2 (a story I have also told in this post). Such displacement at silicon famously proceeds by a quite different mechanism, which I here quantify with some calculations.
The original strategic objective of my PhD researches in 1972-74 was to explore how primary kinetic hydrogen isotope effects might be influenced by the underlying structures of the transition states involved. Earlier posts dealt with how one can construct quantum-chemical models of these transition states that fit the known properties of the reactions.
