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Henry Rzepa's Blog

Henry Rzepa's Blog
Chemistry with a twist
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PericyclicReaction MechanismAnimationBicyclic Ring ProductEnergy Derivative Gradient NormCiencias QuímicasInglés
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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.

Reaction MechanismAmmonia BoraneAnimationBoranesChemistryCiencias QuímicasInglés
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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

Bond SlamInteresting ChemistryBondChemical BondChemical Bond ZooCiencias QuímicasInglés
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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.

Interesting ChemistryWATOC ReportsGas PhaseJournalistMagnetismCiencias QuímicasInglés
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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. Sason Shaik introduced a theme he first investigated years ago, but for which no experiment had been devised for verification. He revived his theme when a journalist contacted him last year to report exactly such an observation, which I now recount.

Interesting ChemistryWATOC ReportsChemical ShiftsChemistryCity: MunichCiencias QuímicasInglés
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Another selection (based on my interests, I have to repeat) from WATOC 2017 in Munich. Odile Eisenstein gave a talk about predicted^ 13^C 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.

Interesting ChemistryWATOC ReportsBond Dissociation EnergyCity: AachenCity: MunichCiencias QuímicasInglés
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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. Edward Valeev talked about the scaling problem in coupled cluster theories, the so-called gold standard for computing the energy and properties of small molecules.

Interesting ChemistryCiencias QuímicasInglés
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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.

Bond SlamInteresting ChemistryCiencias QuímicasInglés
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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.

GeneralAnimal DanceBeeBehaviorFlowerCiencias QuímicasInglés
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Bees are having a tough time around the world. Oddly, they are surviving very well in cities. One reason are the wild flower meadows in London and for some summer relief I thought I would tell you the story of the one shown below. We live in west London, in an area that was farmland as recently as the 1930s and used to produce vegetables and milk for the population of London.

Chemical ITCiencias QuímicasInglés
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There is much focus at the moment on how to ensure experimental replicability in e.g. the molecular sciences. An important aspect of that is having access to FAIR data; data which is findable, accessible, inter-operable and re-usable. One of the “gold standards” in chemistry is the data associated with crystal structures.