This comes to you from China, and the city of Suzhou. To set the scene, cities in China have a lot of motorbikes. Electric ones. With their own speed units, a % of Panda speed. Msny msny people ride bikes such as these; some even manage three passengers, or several boxes of shopping. And the streets will have dedicated lanes for them, although you do need eyes in the back of your head to spot their silent (often 15 kph) approach.

A fascinating re-examination has appeared[cite]10.1002/anie.201505482[/cite] of a reaction first published[cite]10.1002/ange.19600721210[/cite] in 1960 by Wittig and then[cite]10.1002/jlac.19646790106[/cite] repudiated by him in 1964 since it could not be replicated by a later student.

How does an anaesthetic work?

Previously, I explored deviation from ideal tetrahedral arrangements of four carbon ligands around a central (sp ³ ) carbon using crystal structures. Now it is the turn of digonal (sp ¹ ) and trigonal (sp ² ) carbons.  Firstly, the digonal C≡C case. Attached to each carbon of the C≡C unit are two saturated carbon ligands; this to prevent conjugation from influencing our result.

An article entitled " Four Decades of the Chemistry of Planar Hypercoordinate Compounds "[cite]10.1002/anie.201410407[/cite] was recently reviewed by Steve Bacharach on his blog, where you can also see comments. Given the recent crystallographic themes here, I thought I might try a search of the CSD (Cambridge structure database) to see whether anything interesting might emerge for tetracoordinate carbon.

The previous post explored the structural features of amides. Here I compare the analysis with that for the closely related thioamides. Here is the torsional analysis around the C-N bond. The “diff” (difference) is that almost all the hits are concentrated into angles of 0° or 180°; the twist about the C-N bond from co-planarity is much less if S is present.

The π-resonance in amides famously helped Pauling to his proposal of a helical structure for proteins. Here I explore some geometric properties of amides related to the C-N bond and the torsions about it. The key aspect of amides is that a lone pair of electrons on the nitrogen can conjugate with the C=O carbonyl only if the lone pair orbital is parallel to the C-O π-system.

The first conference devoted to scientific uses of Wikipedia has just finished; there was lots of fascinating stuff but here I concentrate on one report that I thought was especially interesting. To introduce it, I need first to introduce WikiData. This is part of the WikiMedia ecosystem, and one of the newest. The basic concept is really simple. It is a repository for data objects; 14,757,419 of them as I write this to be precise.

Most visitors to London use the famous underground trains (the “tube”) or a* double-decker bus* to see the city (one can also use rivers and canals). So I thought, during the tourism month of August, I would show you an alternative overground circumnavigation of the city using the metaphor of benzene. Benzene you see is a ring, comprising three “HCCH” segments.

The anomeric effect is best known in sugars, occuring in sub-structures such as RO-C-OR. Its origins relate to how the lone pairs on each oxygen atom align with the adjacent C-O bonds. When the alignment is 180°, one oxygen lone pair can donate into the C-O σ* empty orbital and a stabilisation occurs. Here I explore whether crystal structures reflect this effect.

Previously, I showed how conjugation in dienes and diaryls can be visualised by inspecting bond lengths as a function of torsions.