Archive for the ‘Interesting chemistry’ Category
Tuesday, December 6th, 2011
My previous three posts set out my take on three principle categories of pericyclic reaction. Here I tell a prequel to the understanding of these reactions. In 1965, Woodward and Hoffmann[1] in their theoretical analysis (submitted Nov 30, 1964) for which the Nobel prize (to Hoffmann only of the pair, Woodward having died) was later awarded. But in the same year, Elias Corey[2] reported the conclusion of a project started several years earlier (first reported (DOI: 10.1021/ja00907a030, Nov 1, 1963) to synthesize the sesquiterpene dihydrocostunolide.
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References
- R.B. Woodward, and R. Hoffmann, "Stereochemistry of Electrocyclic Reactions", Journal of the American Chemical Society, vol. 87, pp. 395-397, 1965. https://doi.org/10.1021/ja01080a054
- E.J. Corey, and A.G. Hortmann, "The Total Synthesis of Dihydrocostunolide", Journal of the American Chemical Society, vol. 87, pp. 5736-5742, 1965. https://doi.org/10.1021/ja00952a037
Tags:electrocyclic, Elias Corey, Historical, pericyclic, photochemical, photochemical product, Tutorial material
Posted in Interesting chemistry | 2 Comments »
Friday, November 25th, 2011
In the previous post, I wrote about the processes that might be involved in a molecular wheel rotating. A nano car has four wheels, and surely the most amazing thing is how the wheels manage to move in synchrony. This is one hell of a tough problem, and I do not attempt an answer here, but simply record an odd observation.
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Tags:animation, nano car
Posted in Interesting chemistry | 2 Comments »
Sunday, November 13th, 2011
Following 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
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Tags:200-300, by-product, Christopher Ingold, energy, free energy, Hilda Usherwood, Historical, Imperial College, Martha Whitely, microwave, polymerization, RSC Publishing, United Kingdom
Posted in Interesting chemistry | 2 Comments »
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[1]. 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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References
- T. Kudernac, N. Ruangsupapichat, M. Parschau, B. Maciá, N. Katsonis, S.R. Harutyunyan, K. Ernst, and B.L. Feringa, "Electrically driven directional motion of a four-wheeled molecule on a metal surface", Nature, vol. 479, pp. 208-211, 2011. https://doi.org/10.1038/nature10587
Tags:car drives, car rattling, chemical concepts, chemical name atropisomerism, chemical perspective, conformational analysis, day devices, energy, energy difference, Hubert Maehr, molecular car, nanocar, PDF, smallest car, Taxol
Posted in General, Interesting chemistry | 3 Comments »
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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Tags:attosecond, chemical processes, exasecond, free energy barrier, G/RT, Inga Ulusoy, laser, Mathias Nest, Tutorial material
Posted in General, Interesting chemistry | 1 Comment »
Tuesday, November 1st, 2011
My previous post introduced the interesting guts of taxol. Two different isomers can exist, and these are called atropisomers; one has the carbonyl group pointing up, the other down. The barrier to their interconversion in this case is generated by a rotation about the two single bonds connecting the carbonyl group to the rest of the molecule. Introductory chemistry tells us that the barrier for rotation about such single bonds is low (i.e. fast at room temperature). But is that true here?
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Tags:animation, conformational analysis, Taxol, Tutorial material
Posted in Interesting chemistry | 4 Comments »
Friday, October 28th, 2011
Moore’s law describes a long-term trend in the evolution of computing hardware, and it is often interpreted in terms of processing speed. Here I chart this rise in terms of the size of computable molecules. By computable I mean specifically how long it takes to predict the geometry of a given molecule using a quantum mechanical procedure.
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Tags:3g, chemical engineers, chemical reactor plants, computational chemistry, energy, energy function, hallucination, Historical, LSD, molecular systems, Paul Weiner, simulation, sojourn, Texas Tavern, X-ray
Posted in Interesting chemistry | No Comments »
Friday, October 21st, 2011
Organic chemists have been making (more or less pure) molecules for the best part of 180 years. Occasionally, these ancient samples are unearthed in cupboards, and then the hunt for their origin starts. I have previously described tracking down the structure of a 120 year-old sample of a naphthalene derivative. But I visited a colleague's office today, and recollected having seen a well-made wooden display cabinet there on a previous visit. Today I took a photo of one of the samples:
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Tags:August von Hofmann, chemicals, detective, first professor, Haifa, Historical, Institute of Technology, professor of organic chemistry in the UK, Technion, United Kingdom, worth preserving chemical samples
Posted in Interesting chemistry | 1 Comment »
Sunday, October 16th, 2011
I asked a while back whether blogs could be considered a serious form of scholarly scientific communication (and so has Peter Murray-Rust more recently). A case for doing so might be my post of about a year ago, addressing why borane reduces a carboxylic acid, but not its ester, where I suggested a possible mechanism. Well, colleagues have raised some interesting questions, both on the blog itself and more silently by email to me. As a result, I have tried to address some of these questions, and accordingly my original scheme needs some revision! This sort of iterative process of getting to the truth with the help of the community (a kind of crowd-sourced chemistry) is where I feel blogs do have a genuine role to play.
The reduction of a carboxylic acid by borane
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Tags:activation energy, animation, carboxylic acid, carboxylic ester, diborane, free energy, pericyclic, Peter Murray-Rust, Reaction Mechanism, reduction, Tutorial material
Posted in Interesting chemistry | 8 Comments »
