Peter Edwards has just given the 2015 Hofmann lecture here at Imperial on the topic of solvated electrons . An organic chemist knows this species as “ e – ” and it occurs in ionic compounds known as electrides ; chloride = the negative anion of a chlorine atom, hence electride = the negative anion of an electron.
Recollect this earlier post on the topic of the Baeyer-Villiger reaction. In 1999 natural abundance kinetic isotope effects were reported[cite]10.1021/ja992016z[/cite] and I set out to calculate the values predicted for a particular model constructed using Quantum mechanics. This comparison of measurement and calculation is nowadays a standard verification of both experiment and theory.
Open principles in the sciences in general and chemistry in particular are increasingly nowadays preached from funding councils down, but it can be more of a challenge to find innovative practitioners. Part of the problem perhaps is that many of the current reward systems for scientists do not always help promote openness.
The university sector in the UK has quality inspections of its research outputs conducted every seven years, going by the name of REF or Research Excellence Framework. The next one is due around 2020, and already preparations are under way! Here I describe how I have interpreted one of its strictures;
In the preceding post, I discussed the reaction between mCPBA (meta-chloroperbenzoic acid) and cyclohexanone, resulting in Baeyer-Villiger oxidation via a tetrahedral intermediate (TI). Dan Singleton, in whose group the original KIE (kinetic isotope measurements) were made, has kindly pointed out on this blog that his was a mixed-phase reaction, and that mechanistic comparison with homogenous solutions may not be
I have blogged before about the mechanism of this classical oxidation reaction. Here I further explore computed models, and whether they match the observed kinetic isotope effects (KIE) obtained using the natural-abundance method described in the previous post. There is much previous study of this rearrangement, and the issue can be reduced to deciding whether TS1 or TS2 is rate-limiting.
My PhD thesis involved determining kinetic isotope effects (KIE) for aromatic electrophilic substitution reactions in an effort to learn more about the nature of the transition states involved.[cite]10.1039/p29750001209[/cite] I learnt relatively little, mostly because a transition state geometry is defined by 3N-6 variables (N = number of atoms) and its force constants by even more and you get only one or two measured KIE per reaction;
I am on a mission to persuade my colleagues that the statistical analysis of crystal structures is a useful teaching tool.
As I have noted elsewhere, Gilbert N. Lewis wrote a famous paper entitled “ the atom and the molecule ”, the centenary of which is coming up.[cite]10.1021/ja02261a002[/cite] In a short and rarely commented upon remark, he speculates about the shared electron pair structure of acetylene, R-X≡X-R (R=H, X=C). It could, he suggests, take up three forms. H-C:::C-H and two more which I show as he drew them.
A lunchtime conversation with a colleague had us both bemoaning the distorting influence on chemistry of bibliometrics, h-indices and journal impact factors, all very much a modern phenomenon of scientific publishing. Young academics on a promotion fast-track for example are apparently advised not to publish in a well-known journal devoted to organic chemistry because of its apparently “low” impact factor.
The Bürgi–Dunitz angle is one of those memes that most students of organic chemistry remember. It hypothesizes the geometry of attack of a nucleophile on a trigonal unsaturated (sp 2 ) carbon in a molecule such as ketone, aldehyde, ester, and amide carbonyl.
