Steve Bachrach on his own blog has commented on a recent article[cite]10.1002/anie.201505934[/cite] discussing the structure of the trimer of fluoroethanol. Rather than the expected triangular form with three OH—O hydrogen bonds, the lowest energy form only had two such bonds, but it matched the microwave data much better. Here I explore this a bit more.
Interactions responsible for the lowest energy structure of the trimer of fluoroethanol.
October 23rd, 2015Pierre and Marie Curie.
October 23rd, 2015I have previously shown the grave of William Perkin, a great british organic chemist. On a recent visit to Paris, I went to see the crypt in the Panthéon, the great french secular necropolis. What a contrast to Perkin!
Impressions of China 2: The colour of porcelain.
October 14th, 2015In Jingdezhen an Imperial Kiln was built in 1369 to produce porcelain that was “white as jade, thin as paper, bright as a mirror and tuneful as a bell”. It’s the colours of the glazes that caught my eye, achieved by a combination of oxidative and reductive firing in the kiln, coupled with exquisite control of the temperature.
Impressions of China. New units of speed and old ways of counting.
October 9th, 2015This 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. 
Isoelectronic games: the CO analogue of diazirines as an intriguing species?
September 24th, 2015How does an anaesthetic work? Surprisingly, it is only recently[cite]10.1038/nchembio.1340[/cite] that the possible binding sites of the anaesthetic propofol (2,6-di-isopropylphenol) have been identified using a technique known as photoaffinity labelling.[cite]10.1016/j.bmc.2011.06.066[/cite] A propofol analogue was constructed[cite]10.1038/nchembio.1340[/cite] by replacing one of the isopropyl groups with a trifluoromethyl diazirine group (R=CF3, X=Y=N below). Upon photolysis, this species looses nitrogen and forms a carbene as a reactive species, which with further chemistry binds covalently[cite]10.1016/j.bmc.2011.06.066[/cite] to adjacent amino acids in the binding pocket.These modified segments could then be analysed by mass spectrometry.[cite]10.1038/nchembio.1340[/cite] An isomer of diazirine is diazomethane, which is some 11 kcal/mol lower in free energy, but fortunately the diazirene is preventing from thermally isomerising to this species by a large kinetic barrier. That was the intro; now for a connection.‡ I recently attended a presentation on another medical topic, the therapeutic uses of carbon monoxide.[cite]10.1038/nrd3228[/cite] In higher concentrations it is notoriously lethal, but with appropriate delivery it can be therapeutic. So, intertwingling, I asked myself what the properties of the carbon monoxide isoelectronic analogue of a diazirine might be (X=C, Y=O below).
Deviations from planarity of trigonal carbon and from linearity of digonal carbon.
September 13th, 2015Previously, I explored deviation from ideal tetrahedral arrangements of four carbon ligands around a central (sp3) carbon using crystal structures. Now it is the turn of digonal (sp1) and trigonal (sp2) carbons.
π-Resonance in thioamides: a crystallographic “diff” with amides.
September 5th, 2015The previous post explored the structural features of amides. Here I compare the analysis with that for the closely related thioamides.
π-Resonance in amides: a crystallographic reality check.
September 5th, 2015The 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.