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Henry Rzepa's Blog

Henry Rzepa's Blog
Chemistry with a twist
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Chemical ITGeneralInteresting ChemistryChairChemical ConnectionsCiencias QuímicasInglés
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Peter Murray-Rust in his blog asks for examples of the Scientific Semantic Web, a topic we have both been banging on about for ten years or more (DOI: 10.1021/ci000406v). What we are seeking of course is an example of how scientific connections have been made using inference logic from semantically rich statements to be found […]

GeneralAromatic SystemsHttpMissouriRemi ChauvinCiencias QuímicasInglés
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Some molecules, when you first see them, just intrigue. So it was with carbobenzene, the synthesis of a derivative of which was recently achieved by Remi Chauvin and co-workers (DOI: 10.1002/chem.200601193). Two additional carbon atoms have been inserted into each of the six C-C bonds in benzene.

Interesting ChemistryAppropriate AlgorithmsConformational AnalysisEnergy GapHere ICiencias QuímicasInglés
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Here I offer another spin-off from writing a lecture course on conformational analysis. This is the famous example of why 1,2-difluoroethane adopts a gauche rather than antiperiplanar conformation.

Interesting ChemistryFree EnergyFree Energy BarrierMetal CatalystsNucleotide Synthesizer TechnologiesCiencias QuímicasInglés
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One future vision for chemistry over the next 20 years or so is the concept of having machines into which one dials a molecule, and as if by magic, the required specimen is ejected some time later. This is in some ways an extrapolation of the existing peptide and nucleotide synthesizer technologies and sciences.

HypervalencyBondingELFFluorineHiberty And CoCiencias QuímicasInglés
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In the previous post, I ruminated about how chemists set themselves targets. Thus, having settled on describing regions between two (and sometimes three) atoms as bonds, they added a property of that bond called its order. The race was then on to find molecules which exhibit the highest order between any particular pair of atoms.

HypervalencyGas PhaseMt. EverestPenceCiencias QuímicasInglés
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Climbers scale Mt. Everest, because its there, and chemists have their own version of this. Ever since G. N. Lewis introduced the concept of the electron-pair bond in 1916, the idea of a bond as having a formal bond-order has been seen as a useful way of thinking about molecules.

Interesting ChemistryChairConformational AnalysisFinal Resting EnergyFree EnergyCiencias QuímicasInglés
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In an earlier post, I re-visited the conformational analysis of cyclohexane by looking at the vibrations of the entirely planar form (of D6h symmetry). The method also gave interesting results for the larger cyclo-octane ring. How about a larger leap into the unknown?