An original chemistry lab from the early 19th century.

May 18th, 2014

Not a computer in sight! I refer to a chemistry lab from the 1800s I was recently taken to, where famous french chemists such as Joseph Gay-Lussac, Michel Chevreul and Edmond Fremy were professors. Although not used for chemistry any more, it is an incredible treasure trove of objects. Here are photos of some.

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A newcomer in the game of how we find and use data.

May 17th, 2014

I remember a time when tracking down a particular property of a specified molecule was an all day effort, spent in the central library (or further afield). Then came the likes of STN Online (~1980) and later Beilstein. But only if your institution had a subscription. Let me then cut to the chase: consider this URL: http://search.datacite.org/ui?q=InChIKey%3DLQPOSWKBQVCBKS-PGMHMLKASA-N The site is datacite, which collects metadata about cited data! Most of that data is open in the sense that it can be retrieved without a subscription (but see here that it is not always made easy to do so). So, the above is a search for cited data which contains the InChIkey LQPOSWKBQVCBKS-PGMHMLKASA-N. This produces the result:
datacite1
This tells you who published the data (but oddly, its date is merely to the nearest year? It is beta software after all). The advanced equivalent of this search looks like this:

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Disambiguation/provenance of claimed scientific opinion and research.

May 5th, 2014

My name is displayed pretty prominently on this blog, but it is not always easy to find out who the real person is behind many a blog. In science, I am troubled by such anonymity. Well, a new era is about to hit us. When you come across an Internet resource, or an opinion/review of some scientific topic, I argue here that you should immediately ask: “what is its provenance?”

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Trigonal bipyramidal or square pyramidal: Another ten minute exploration.

May 2nd, 2014

This is rather cranking the handle, but taking my previous post and altering the search definition of the crystal structure database from 4- to 5-coordinate metals, one gets the following.

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Tetrahedral or square planar? A ten minute exploration.

April 30th, 2014

I love experiments where the insight-to-time-taken ratio is high. This one pertains to exploring the coordination chemistry of the transition metal region of the periodic table; specifically the tetra-coordination of the series headed by Mn-Ni. Is the geometry tetrahedral, square planar, or other? One can get a statistical answer in about ten minutes.
Tet-SP.jpgThe (CCDC database) search definition required is shown above. The central atom defines the column of the period table, it is specified to have precisely four other atoms bonded to it, which can be any other element. These four bonds are specified as acyclic (to avoid any bias introduced by rings). And two angles are defined subtending the central atom. And off we go, defining on the way that the hits must be refined to an R-factor of < 0.05, have no disorder, and no errors.

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Ribulose-1,5-bisphosphate + carbon dioxide → carbon fixation!

April 20th, 2014

Ribulose-1,5-bisphosphate reacts with carbon dioxide to produce 3-keto-2-carboxyarabinitol 1,5-bisphosphate as the first step in the biochemical process of carbon fixation. It needs an enzyme to do this (Ribulose-1,5-bisphosphate carboxylase/oxygenase, or RuBisCO) and lots of ATP (adenosine triphosphate, produced by photosynthesis). Here I ask what the nature of the uncatalysed transition state is, and hence the task that might be facing the catalyst in reducing the activation barrier to that of a facile thermal reaction. I present my process in the order it was done.

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More (blog) connections spotted. Something new about diphenyl magnesium?

April 17th, 2014

I have just noticed unexpected links between two old posts, one about benzene, one about diphenyl magnesium and a link to August Kekulé.

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Enantioselective epoxidation of alkenes using the Shi Fructose-based catalyst. An undergraduate experiment.

April 15th, 2014

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.[1] 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. 

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References

  1. A. Burke, P. Dillon, K. Martin, and T.W. Hanks, "Catalytic Asymmetric Epoxidation Using a Fructose-Derived Catalyst", J. Chem. Educ., vol. 77, pp. 271, 2000. http://dx.doi.org/10.1021/ed077p271

Artemisinin: are stereo-electronics at the core of its (re)activity?

April 13th, 2014

Around 100 tons of the potent antimalarial artemisinin is produced annually; a remarkable quantity given its very unusual and fragile looking molecular structure (below). When I looked at this, I was immediately struck by a thought: surely this is a classic molecule for analyzing stereoelectronic effects (anomeric and gauche). Here this aspect is explored.

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A connected world (journals and blogs): The benzene dication.

April 10th, 2014

Science is rarely about a totally new observation or rationalisation, it is much more about making connections between known facts, and perhaps using these connections to extrapolate to new areas (building on the shoulders of giants, etc). So here I chart one example of such connectivity over a period of six years.

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