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.

Previously on this blog: modelling the reduction of cinnamaldehyde using one molecule of lithal shows easy reduction of the carbonyl but a high barrier at the next stage, the reduction of the double bond.

According to Guggemos, Slavicek and Kresin, about 5-6![cite]10.1103/PhysRevLett.114.043401[/cite]. This is one of those simple ideas, which is probably quite tough to do experimentally. It involved blasting water vapour through a pinhole, adding HCl and measuring the dipole-moment induced deflection by an electric field.

Sometimes you come across a bond in chemistry that just shouts at you. This happened to me in 1989[cite]10.1039/C39890001722[/cite] with the molecule shown below. Here is its story and, 26 years later, how I responded. To start at the beginning, there was a problem with the measured ¹ H NMR spectrum; specifically (Y=H, Z=O) there are supposedly 16 protons, but only 15 could be located. What had happened to the 16th?

We are approaching 1 million recorded crystal structures (actually, around 716,000 in the CCDC and just over 300,00 in COD). One delight with having this wealth of information is the simple little explorations that can take just a minute or so to do. This one was sparked by my helping a colleague update a set of interactive lecture demos dealing with stereochemistry.

The Bürgi–Dunitz angle describes the trajectory of an approaching nucleophile towards the carbon atom of a carbonyl group. A colleague recently came to my office to ask about the inverse, that is what angle would an electrophile approach (an amide)? Thus it might approach either syn or anti with respect to the nitrogen, which is a feature not found with nucleophilic attack.

The journal of chemical education can be a fertile source of ideas for undergraduate student experiments. Take this procedure for asymmetric epoxidation of an alkene.[cite]10.1021/ed077p271[/cite] When I first spotted it, I thought not only would it be interesting to do in the lab, but could be extended by incorporating some modern computational aspects as well.

In the previous post, I showed how modelling of unbranched alkenes depended on dispersion forces. When these are included, a bent (single-hairpin) form of C ₅₈ H ₁₁₈ becomes lower in free energy than the fully extended linear form. Here I try to optimise these dispersion forces by adding further folds to see what happens.

By about C17H36, the geometry of “cold-isolated” unbranched saturated alkenes is supposed not to contain any fully anti-periplanar conformations.

Mercury (IV) tetrafluoride attracted much interest when it was reported in 2007[cite]10.1002%2Fanie.200703710[/cite] as the first instance of the metal being induced to act as a proper transition element (utilising d-electrons for bonding) rather than a post-transition main group metal (utilising just s-electrons) for which the HgF ₂ dihalide would be more normal (“Is mercury now a transition