October 5th, 2017
We have heard a lot about OA or Open Access (of journal articles) in the last five years, often in association with the APC (Article Processing Charge) model of funding such OA availability. Rather less discussed is how the model of the peer review of these articles might also evolve into an Open environment. Here I muse about two experiences I had recently.
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Tags: Academic publishing, article processing charge, author, Company: Facebook, Company: Publons, Company: Twitter, editor, Electronic publishing, Entertainment/Culture, Hybrid open access journal, Internet giants, OA, Open access, Organic Syntheses, Public sphere, Publishing, Scholarly communication, search engines, Social Media & Networking, Technology/Internet
Posted in Chemical IT, General | 5 Comments »
October 1st, 2017
I noted in my WATOC conference report a presentation describing the use of calculated reaction barriers (and derived rate constants) as mechanistic reality checks. Computations, it was claimed, have now reached a level of accuracy whereby a barrier calculated as being 6 kcal/mol too high can start ringing mechanistic alarm bells. So when I came across this article[cite]10.1021/acs.orglett.7b01621[/cite] in which calculated barriers for a dyotropic ring expansion observed under mild conditions in dichloromethane as solvent were used to make mechanistic inferences, I decided to explore the mechanism a bit further.
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Tags: animation, bicyclic ring product, energy derivative gradient norm, energy profile, final non-ionic product, Organic chemistry, possible products, potential energy surface, realistic model for the reaction
Posted in pericyclic, reaction mechanism | 3 Comments »
September 21st, 2017
A recent article reports, amongst other topics, a computationally modelled reaction involving the capture of molecular hydrogen using a substituted borane (X=N, Y=C).[cite]10.1073/pnas.1709586114[/cite] The mechanism involves an initial equilibrium between React and Int1, followed by capture of the hydrogen by Int1 to form a 5-coordinate borane intermediate (Int2 below, as per Figure 11).‡ This was followed by assistance from a proximate basic nitrogen to complete the hydrogen capture via a TS involving H-H cleavage. The forward free energy barrier to capture was ~11 kcal/mol and ~4 kcal/mol in the reverse direction (relative to the species labelled Int1), both suitably low for reversible hydrogen capture. Here I explore a simple variation to this fascinating reaction.∞
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Tags: Ammonia borane, animation, Boranes, Chemistry, Cleaning Services, Company: React Group, free energy barrier, Hydroboration, Hydrogen, Matter
Posted in reaction mechanism | 1 Comment »
September 16th, 2017
Early in 2011, I wrote about how the diatomic molecule Be2 might be persuaded to improve upon its normal unbound state (bond order ~zero) by a double electronic excitation to a strongly bound species. I yesterday updated this post with further suggestions and one of these inspired this follow-up.
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Tags: Be-Be double bond, Be-Be triple bond, Chemical bond, Chemistry, Cs-Cs double bond, Diatomic molecule, free energy, General chemistry, K-K double bond, Li-Li double bond, Molecular geometry, Oxygen, Province/State: Be2, Quantum chemistry, Rb-Rb double bond, Stereochemistry
Posted in Interesting chemistry | 3 Comments »
September 6th, 2017
The chemical bond zoo is relatively small (the bond being a somewhat fuzzy concept, I am not sure there is an actual count of occupants). So when two new candidates come along, it is worth taking notice. I have previously noted the Chemical Bonds at the 21st Century-2017: CB2017 Aachen conference, where both were discussed.
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Tags: bond, Chemical bond, chemical bond zoo, City: Aachen, Concepts, Dialectic, Fuzzy concept, Non-classical logic, Psychometrics, triplet excitation energy
Posted in Bond slam, Interesting chemistry | No Comments »
August 31st, 2017
Conferences can be intense, and this one is no exception. After five days, saturation is in danger of setting in. But before it does, I include two more (very) brief things I have learnt.
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Tags: gas phase, journalist, Magnetism, Pavel Hobza, Saturation, Semiconductors - NEC, synthetic chemist, ultrasound
Posted in Interesting chemistry, WATOC reports | 4 Comments »
August 29th, 2017
Another selection (based on my interests, I have to repeat) from WATOC 2017 in Munich.
- Odile Eisenstein gave a talk about predicted 13C chemical shifts in transition metal (and often transient) complexes, with the focus on metallacyclobutanes. These calculations include full spin-orbit/relativistic corrections, essential when the carbon is attached to an even slightly relativistic element. She noted that the 13C shifts of the carbons attached to the metal fall into two camps, those with δ ~+80 ppm and those with values around -8 ppm. These clusters are associated with quite different reactivities, and also seem to cluster according to the planarity or non-planarity of the 4-membered ring. There followed some very nice orbital explanations which I cannot reproduce here because my note taking was incomplete, including discussion of the anisotropy of the solid state spectra. A fascinating story, which I add to here in a minor aspect. Here is a plot of the geometries of the 52 metallacyclobutanes found in the Cambridge structure database. The 4-ring can be twisted by up to 60° around either of the C-C bonds in the ring, and rather less about the M-C bonds. There is a clear cluster (red spot) for entirely flat rings, and perhaps another at around 20° for bent ones, but of interest is that it does form something of a continuum. What is needed is to correlate these geometries with the observed 13C chemical shifts to see if the two sets of clusters match. I include this here because in part such a search can be done in “real-time” whilst the speaker is presenting, and can then be offered as part of the discussion afterwards. It did not happen here because I was chairing the meeting, and hence concentrating entirely on proceedings!
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Tags: chemical shifts, Chemistry, City: Munich, Jan Jenson, metal fall, Munich, Odile Eisenstein, Quotation, speaker, Stefan Grimme, Transition metal, Walter Thiel, World Association of Theoretical and cOmputational Chemists
Posted in Interesting chemistry, WATOC reports | 6 Comments »
August 29th, 2017
The triennial conference is this year located in Munich. With 1500 participants and six parallel sessions, this report can give only a flavour of proceedings.
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Tags: bond dissociation energy, City: Aachen, City: Munich, Dieter Cremer, Edward Valeev, energy, Flavour, Jeremy Harvey, Ken Houk, Leo Radom, Peter Scheiner, Physics, Proceedings, Quark matter, Standard Model, Yitzhak Apeloig
Posted in Interesting chemistry, WATOC reports | No Comments »
August 12th, 2017
At the moment, the bond slam is something of a home from home for this blog and since much of my activity is happening there rather than here, I thought I might give you pointers to some of the topics, which are evolving, so to speak, before our very eyes.
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Posted in Interesting chemistry | No Comments »
August 2nd, 2017
It is always interesting to observe conference experiments taking place. The traditional model involves travelling to a remote venue, staying in a hotel, selecting sessions to attend from a palette of parallel streams and then interweaving chatting to colleagues both old and new over coffee, lunch, dinner or excursions. Sometimes conferences occur in clusters, with satellite meetings breaking out in the vicinity, after a main conference has done the job of attracting delegates to the region. Here I bring to your attention one such experiment, the Bond Slam which is part of a satellite meeting in Aachen to be held September 2-4 2017 on the topic of Chemical Bonds at the 21st Century, following on from the WATOC 2017 congress in Munich Germany a few days earlier.
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Posted in Bond slam, Interesting chemistry | 3 Comments »