I am now inverting the previous question by asking what is the largest angle subtended at a chain of three connected 4-coordinate carbon atoms ? Let’s see if further interesting chemistry can be unearthed. Specifying only angles > 130°, the following distribution is obtained.

This is another in the occasional series of “what a neat molecule”. In this case, more of a “what a neat idea”. The s-triazine below, when coordinated to eg ZnI ₂ , forms what is called a metal-organic-framework, or MOF. A recent article[1] shows how such frameworks can be used to help solve a long-standing problem in structure determination, how to get a crystal structure on a compound that does not crystallise on its own.

Functionalisation of a (hetero)aromatic ring by selectively (directedly) removing protons using the metal lithium is a relative mechanistic newcomer, compared to the pantheon of knowledge on aromatic electrophilic substitution. Investigating the mechanism using quantum calculations poses some interesting challenges, ones I have not previously discussed on this blog.

If you search e.g. Scifinder for N,O-diphenyl hydroxylamine (RN 24928-98-1) there is just one literature citation, to a 1962 patent. Nothing else;

The text books say that cyclohexenone A will react with a Grignard reagent by delivery of an alkyl (anion) to the carbon of the carbonyl ( 1,2-addition ) but if dimethyl lithium cuprate is used, a conjugate 1,4-addition proceeds, to give the product B shown below.

Every once in a while, one encounters a molecule which instantly makes an interesting point.

Alkene metathesis is part of a new generation of synthetic reaction in which a double C=C bond is formed from appropriate reactants where no bond initially exists (another example is the Wittig reaction), with the involvement ^† of a 4-membered-ring metallacyclobutane ring 1 (again, very similar to the Wittig). I thought it might make a good addition to my collection of reaction mechanisms and so as the first step

The (hopefully tongue-in-cheek) title Mindless chemistry was given to an article reporting[1] an automated stochastic search procedure for locating all possible minima with a given composition using high-level quantum mechanical calculations. “Many new structures, often with nonintuitive geometries, were found”. Well, another approach is to follow unexpected hunches.

The Grignard reaction is encountered early on in most chemistry courses, and most labs include the preparation of this reagent, typically by the following reaction: 2PhBr + 2Mg → 2PhMgBr ↔︎ MgBr ₂ + Ph ₂ Mg The reagent itself exists as part of an equilibrium, named after Schlenk, in which a significant concentration of a dialkyl or diarylmagnesium species is formed.