Archive for the ‘General’ Category

A curly-arrow pushing manual

Wednesday, December 4th, 2013

I 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.

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Blasts from the past and present: altmetrics.

Sunday, October 13th, 2013

I reminisced about the wonderfully naive but exciting Web-period of 1993-1994. This introduced the server-log analysis to us for the first time, and hits-on-a-web-page. One of our first attempts at crowd-sourcing and analysis was to run an electronic conference in heterocyclic chemistry and to look at how the attendees visited the individual posters and presentations by analysing the server logs.

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The demographics of a blog readership.

Sunday, January 20th, 2013

With metrics in science publishing controversial to say the least, I pondered whether to write about the impact/influence a science-based blog might have (never mind whether it constitutes any measure of esteem). These are all terms that feature large when an (academic) organisation undertakes a survey of its researchers’ effectiveness. WordPress (the organisation that provides the software used for this blog) recently enhanced the stats it offers for its users, and one of these caught my eye.

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Transition state models for Baldwin’s rules of ring closure.

Saturday, June 2nd, 2012

The Baldwin rules for ring closure follow the earlier ones by Bürgi and Dunitz in stating the preferred angles of nucleophilic (and electrophilic) attack in bond forming reactions, and are as famous for the interest in their exceptions as for their adherence. Both sets of rules fundamentally explore the geometry of the transition states involved in the reaction, as reflected in the activation free energies. Previous posts exploring the transition states for well-known reactions have revealed that the 4th dimension (the timing of the bond formations/breakings) can often spring surprises. So this post will explore a typical Baldwin ring formation in the same way.

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Mechanism of the diazomethane alkylation of a carboxylic acid.

Saturday, May 19th, 2012

Many reaction mechanisms involve a combination of bond formation/cleavage between two non-hydrogen atoms and those involving reorganisation of proximate hydrogens. The Baeyer-Villiger discussed previously illustrated a complex dance between the two types. Here I take a look at another such mechanism, the methylation of a carboxylic acid by diazomethane.

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“Text” Books in a (higher) education environment.

Friday, May 18th, 2012

Text books (is this a misnomer, much like “papers” are in journals?) in a higher-educational chemistry environment, I feel, are at a cross-roads. What happens next?

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Shared space (in science).

Friday, January 6th, 2012

I thought I would launch the 2012 edition of this blog by writing about shared space. If you have not come across it before, it is (to quote Wikipedia), “an urban design concept aimed at integrated use of public spaces.” The BBC here in the UK ran a feature on it recently, and prominent in examples of shared space in the UK was Exhibition Road. I note this here on the blog since it is about 100m from my office.

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Driving the smallest car ever made: a chemical perspective.

Thursday, November 10th, 2011

Fascination with nano-objects, molecules which resemble every day devices, is increasing. Thus the world’s smallest car has just been built[cite]10.1038/nature10587[/cite]. The mechanics of such a device can often be understood in terms of chemical concepts taught to most students. So I thought I would have a go at this one!

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Chemistry in an attosecond.

Friday, November 4th, 2011

An attosecond is 10-18s. The chemistry that takes place on this timescale is called electron dynamics. For example, it is the time taken for an electron to traverse the 1s orbit in a hydrogen atom. And chemists are starting to manipulate electrons (and hence chemistry) on this timescale; for example a recent article (DOI: 10.1021/ja206193t) describes how to control the electrons in benzene using attosecond laser pulses.

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Spotting the unexpected. Anomeric effects involving alkenes?

Wednesday, November 2nd, 2011

How one might go about answering the question: do alkenes promote anomeric effects? A search of chemical abstracts does not appear to cite any examples (I may have missed them of course, since it depends very much on the terminology you use, and new effects may not yet have any agreed terminology) and a recent excellent review of hyperconjugation does not mention it. Here I show how one might provide an answer.

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