So much to do, so little time to do it. That is my excuse at least. Right from my first post on this blog in 2008 I have tried to enhance it using Jmol, a Java-based applet (normally indicated with the caption Click for 3D). This has been pretty stable for some five years now, but a recent spate of security-based releases of the JRE (Java runtime environment) for desktop computers has impacted, the latest of which was released yesterday (Java 7, V 51). Put simply, when I started, an unsigned applet was fine. Now to run, it can only be a properly signed applet. Fortunately, there are two solutions:
3D-rendered molecular models on this blog: an update.
January 16th, 2014Three-for-one: a pericyclic brain teaser.
January 12th, 2014A game one can play with pericyclic reactions is to ask students to identify what type a given example is. So take for example the reaction below.
A simple pericyclic reaction encapsulating the four thermal selection rules.
January 2nd, 2014As my previous post hints, I am performing my annual spring-clean of lecture notes on pericyclic reactions. Such reactions, and their stereochemistry, are described by a set of selection rules. I am always on the lookout for a simple example which can most concisely summarise these rules. The (hypothetical) one shown below I think nicely achieves this, and raises some interesting issues in the process.
Refactoring my lecture notes on pericyclic reactions.
December 29th, 2013When I first started giving lectures to students, it was the students themselves that acted as human photocopiers, faithfully trying to duplicate what I was embossing on the lecture theatre blackboard with chalk. How times have changed! Here I thought I might summarise my latest efforts to refactor the material I deliver in one lecture course on pericyclic reactions (and because my notes have always been open, you can view them yourself if you wish).
Does forming a Wheland intermediate disrupt all aromaticity?
December 6th, 2013Text books will announce that during aromatic electrophilic substitution, aromaticity is lost by the formation of a Wheland intermediate (and regained by eliminating a proton). Is that entirely true?
A curly-arrow pushing manual
December 4th, 2013I have several times used arrow pushing on these blogs. But since the rules for this convention appear to be largely informal, and there appears to be no definitive statement of them, I thought I would try to produce this for our students. This effort is here shared on my blog. It is what I refer to as the standard version; an advanced version is in preparation. Such formality might come as a surprise to some; arrow-pushing is often regarded as far too approximate to succumb to any definition, although it is of course often examined.
Avoided (pericyclic) anti-aromaticity: Reactions of t-butyl-hydroxycarbene.
November 13th, 2013Not long ago, I described a cyclic carbene in which elevating the carbene lone pair into a π-system transformed it from a formally 4n-antiaromatic π-cycle into a 4n+2 aromatic π-cycle. From an entirely different area of chemistry, another example of this behaviour emerges; Schreiner’s[cite]10.1039/C2SC21555A[/cite] trapping and reactions of t-butyl-hydroxycarbene, as described on Steve Bachrach’s blog. A point I often make is that chemistry is all about connections, and so here I will discuss such a connection.