In a time of change, we often do not notice that Δ = ∫δ. Here I am thinking of network bandwidth, and my personal experience of it over a 46 year period.
Posts Tagged ‘Imperial College’
Digital repositories. An update.
Saturday, July 21st, 2012I blogged about this two years ago and thought a brief update might be in order now. To support the discussions here, I often perform calculations, and most of these are then deposited into a DSpace digital repository, along with metadata. Anyone wishing to have the full details of any calculation can retrieve these from the repository. Now in 2012, such repositories are more important than ever.
Confirming the Fischer convention as a structurally correct representation of absolute configuration.
Tuesday, March 13th, 2012I wrote in an earlier post how Pauling’s Nobel prize-winning suggestion in February 1951 of a (left-handed) α-helical structure for proteins[1] was based on the wrong absolute configuration of the amino acids (hence his helix should really have been the right-handed enantiomer). This was most famously established a few months later by Bijvoet’s[2] definitive crystallographic determination of the absolute configuration of rubidium tartrate, published on August 18th, 1951 (there is no received date, but a preliminary communication of this result was made in April 1950). Well, a colleague (thanks Chris!) just wandered into my office and he drew my attention to an article by John Kirkwood[3] published in April 1952, but received July 20, 1951,‡ carrying the assertion “The Fischer convention is confirmed as a structurally correct representation of absolute configuration“, and based on the two compounds 2,3-epoxybutane and 1,2-dichloropropane. Neither Bijvoet nor Kirkwood seem aware of the other’s work, which was based on crystallography for the first, and quantum computation for the second. Over the years, the first result has become the more famous, perhaps because Bijvoet’s result was mentioned early on by Watson and Crick in their own very famous 1953 publication of the helical structure of DNA. They do not mention Kirkwood’s result. Had they not been familiar with Bijvoet’s[2] result, their helix too might have turned out a left-handed one!
References
- L. Pauling, R.B. Corey, and H.R. Branson, "The structure of proteins: Two hydrogen-bonded helical configurations of the polypeptide chain", Proceedings of the National Academy of Sciences, vol. 37, pp. 205-211, 1951. http://dx.doi.org/10.1073/pnas.37.4.205
- J.M. BIJVOET, A.F. PEERDEMAN, and A.J. van BOMMEL, "Determination of the Absolute Configuration of Optically Active Compounds by Means of X-Rays", Nature, vol. 168, pp. 271-272, 1951. http://dx.doi.org/10.1038/168271a0
- W.W. Wood, W. Fickett, and J.G. Kirkwood, "The Absolute Configuration of Optically Active Molecules", The Journal of Chemical Physics, vol. 20, pp. 561-568, 1952. http://dx.doi.org/10.1063/1.1700491
The dawn of organic reaction mechanism: the prequel.
Sunday, November 13th, 2011Following on from Armstrong’s almost electronic theory of chemistry in 1887-1890, and Beckmann’s radical idea around the same time that molecules undergoing transformations might do so via a reaction mechanism involving unseen intermediates (in his case, a transient enol of a ketone) I here describe how these concepts underwent further evolution in the early 1920s. My focus is on Edith Hilda Usherwood, who was then a PhD student at Imperial College working under the supervision of Martha Whitely.1
Henry Armstrong: almost an electronic theory of chemistry!
Monday, November 7th, 2011Henry Armstrong studied at the Royal College of Chemistry from 1865-7 and spent his subsequent career as an organic chemist at the Central College of the Imperial college of Science and technology until he retired in 1912. He spent the rest of his long life railing against the state of modern chemistry, saving much of his vitriol against (inter alia) the absurdity of ions, electronic theory in chemistry, quantum mechanics and nuclear bombardment in physics. He snarled at Robinson’s and Ingold’s new invention (ca 1926-1930) of electronic arrow pushing with the put down “bent arrows never hit their marks“.‡ He was dismissed as an “old fogy, stuck in a time warp about 1894.”‡ So why on earth would I want to write about him? Read on…
Computers 1967-2011: a personal perspective. Part 1. 1967-1985.
Thursday, July 7th, 2011Computers and I go back a while (44 years to be precise), and it struck me (with some horror) that I have been around them for ~62% of the modern computing era (Babbage notwithstanding, ~1940 is normally taken as the start of the modern computing era). So indulge me whilst I record this perspective from the viewpoint of the computers I have used over this 62% of the computing era. (more…)
Monastral: the colour of blue
Tuesday, March 8th, 2011The story of Monastral is not about a character in the Magic flute, but is a classic of chemical serendipity, collaboration between industry and university, theoretical influence, and of much else. Fortunately, much of that story is actually recorded on film (itself a unique archive dating from 1933 and being one of the very first colour films in existence!). Patrick Linstead, a young chemist then (he eventually rose to become rector of Imperial College) tells the story himself here. It is well worth watching, if only for its innocent social commentary on the English class system (and an attitude to laboratory safety that should not be copied nowadays). Here I will comment only on its colour and its aromaticity.
Copper phthalocyanine
The colour of purple
Thursday, February 24th, 2011One of my chemical heroes is William Perkin, who in 1856 famously (and accidentally) made the dye mauveine as an 18 year old whilst a student of August von Hofmann, the founder of the Royal College of Chemistry (at what is now Imperial College London). Perkin went on to found the British synthetic dyestuffs and perfumeries industries. The photo below shows Charles Rees, who was for many years the Hofmann professor of organic chemistry at the very same institute as Perkin and Hofmann himself, wearing his mauveine tie. A colleague, who is about to give a talk on mauveine, asked if I knew why it was, well so very mauve. It is a tad bright for today’s tastes!
A short history of molecular modelling: 1860-1890.
Saturday, February 5th, 2011In 1953, the model of the DNA molecule led to what has become regarded as the most famous scientific diagram of the 20th century. It had all started 93 years earlier in 1860, at a time when the tetravalency of carbon was only just established (by William Odling) and the concept of atoms as real entities was to remain controversial for another 45 years (for example Faraday, perhaps the most famous scientist alive in 1860 did not believe atoms were real). So the idea of constructing a molecular model from atoms as the basis for understanding chemical behaviour was perhaps bolder than we might think. It is shown below, part of a set built for August Wilhelm von Hofmann as part of the lectures he delivered at the Royal College of Chemistry in London (now Imperial College).