Posts Tagged ‘Julia Contreras-Garcia’
Friday, December 11th, 2015
You might have noticed the occasional reference here to the upcoming centenary of the publication of Gilbert N. Lewis’ famous article entitled “The atom and the molecule“.[1] A symposium exploring his scientific impact and legacy will be held in London on March 23, 2016, exactly 70 years to the day since his death. A list of the speakers and their titles is shown below; there is no attendance fee, but you must register as per the instructions below.
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References
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G.N. Lewis, "THE ATOM AND THE MOLECULE.", Journal of the American Chemical Society, vol. 38, pp. 762-785, 1916. http://dx.doi.org/10.1021/ja02261a002
Tags:Alan Dronsfield, Clark Landis, Durham, France, Gilbert N. Lewis, Interesting chemistry, John Nicholson, Julia Contreras-Garcia, Liverpool, London, Michael Mingos, Nick Greeves, organic chemist, Oxford, Patrick Coffey, professor, Robin Hendry, Royal Society of Chemistry Historical Group, United Kingdom, United States
Posted in Interesting chemistry | 1 Comment »
Wednesday, December 19th, 2012
The Sharpless epoxidation of an allylic alcohol had a big impact on synthetic chemistry when it was introduced in the 1980s, and led the way for the discovery (design?) of many new asymmetric catalytic systems. Each achieves its chiral magic by control of the geometry at the transition state for the reaction, and the stabilizations (or destabilizations) that occur at that geometry. These in turn can originate from factors such as stereoelectronic control or simply by the overall sum of many small attractions and repulsions we call dispersion interactions. Here I take an initial look at these for the binuclear transition state shown schematically below.
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Tags:asymmetric catalytic systems, Bob Hanson, catalysis, Interesting chemistry, Julia Contreras-Garcia, little web site, NCI, non-covalent-analysis, Reaction Mechanism, terminal =CH
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Friday, October 7th, 2011
The properties of electrons are studied by both chemists and physicists. At the boundaries of these two disciplines, sometimes interesting differences in interpretation emerge. One of the most controversial is that due to Bader (for a recent review, see DOI: 10.1021/jp102748b) a physicist who brought the mathematical rigor of electronic topology to bear upon molecules. The title of his review is revealing: “Definition of Molecular Structure: By Choice or by Appeal to Observation?”. He argues that electron density is observable, and that what chemists call a bond should be defined by that observable (with the implication that chemists instead often resort to arbitrary choice). Here I explore one molecule which could be said to be the focus of the differences between physics and chemistry; cis-but-2-ene.
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Tags:CCP, chemical picture, chemist, conformational analysis, energy, General, Interesting chemistry, Julia Contreras-Garcia, physicist
Posted in General, Interesting chemistry | 6 Comments »
Tuesday, May 31st, 2011
The Pirkle reagent is a 9-anthranyl derivative (X=OH, Y=CF3). The previous post on the topic had highlighted DIST1, the separation of the two hydrogen atoms shown below. The next question to ask is how general this feature is. Here we take a look at the distribution of lengths found in the Cambridge data base, and focus on another interesting example.
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Tags:9-anthranyl, Cambridge, disorder, Interesting chemistry, Julia Contreras-Garcia, X-ray
Posted in Interesting chemistry | 1 Comment »
Sunday, May 29th, 2011
Observation of the slow racemization of isobornyl chloride in a polar solvent in 1923-24 by Meerwein led to the recognition that mechanistic interpretation is the key to understanding chemical reactivity. The hypothesis of ion pairs in which a chloride anion is partnered by a carbocation long ago entered the standard textbooks (see DOI 10.1021/ed800058c and 10.1021/jo100920e for background reading). But the intimate secrets of such ion-pairs are still perhaps not fully recognised. Here, to tease some of them them out, I use the NCI method, which has been the subject of several recent posts.
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Tags:chemical reactivity, Interesting chemistry, ion pair, isobornyl, Julia Contreras-Garcia, nnon-covalent-interactions, watoc11
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Wednesday, May 18th, 2011
In earlier posts, I alluded to what might make DNA wind into a left or a right-handed helix. Here I switch the magnification of our structural microscope up a notch to take a look at some more inner secrets.
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Tags:adjacent, adjacent carbonyl, conformational analysis, energy, General, Interesting chemistry, Julia Contreras-Garcia, N Lp, Postscript, Tutorial material, watoc11
Posted in General, Interesting chemistry | 3 Comments »
Saturday, April 9th, 2011
Understanding why and how proteins fold continues to be a grand challenge in science. I have described how Wrinch in 1936 made a bold proposal for the mechanism, which however flew in the face of much of then known chemistry. Linus Pauling took most of the credit (and a Nobel prize) when in a famous paper in 1951 he suggested a mechanism that involved (inter alia) the formation of what he termed α-helices. Jack Dunitz in 2001 wrote a must-read article on the topic of “Pauling’s Left-handed α-helix” (it is now known to be right handed). I thought I would revisit this famous example with a calculation of my own and here I have used the ωB97XD/6-311G(d,p) DFT procedure to calculate some of the energy components of a small helix comprising (ala)6 in both left and right handed form.
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Tags:alpha-helix, aqueous solutions, chiroptical, conformational analysis, dielectric, energy, energy components, high energy species, Historical, Interesting chemistry, Jack Dunitz, Julia Contreras-Garcia, protein, solvation algorithms, Tutorial material, watoc11
Posted in Interesting chemistry | 4 Comments »