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Henry Rzepa's Blog

Henry Rzepa's Blog
Chemistry with a twist
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Interesting ChemistryChemical KineticsChemical ReactionChemistryDeuteriumChimicaInglese
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Five years back, I speculated about the mechanism of the epoxidation of ethene by a peracid, concluding that kinetic isotope effects provided interesting evidence that this mechanism is highly asynchronous and involves a so-called “hidden intermediate”. Here I revisit this reaction in which a small change is applied to the atoms involved.

HistoricalAlan DronsfieldAlizarinAnthraquinone DyesArt MaterialsChimicaInglese
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The Royal Society of Chemistry historical group (of which I am a member) organises two or three one day meetings a year. Yesterday the October meeting covered (amongst other themes) the fascinating history of madder and its approximately synthetic equivalent alizarin.

Interesting ChemistryChimicaInglese
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Here is the concluding part of my exploration of a recently published laboratory experiment for undergraduate students. I had previously outlined a possible mechanistic route, identifying TS3 (below) as the first transition state in which C-C bond formation creates two chiral centres.

Interesting ChemistryAbsolute ConfigurationBiochemistryBulk SolutionsChemical TransformationsChimicaInglese
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I am exploring the fascinating diverse facets of a recently published laboratory experiment for undergraduate students. Previously I looked at a possible mechanistic route for the reaction between an enal (a conjugated aldehyde-alkene) and benzyl chloride catalysed by base and a chiral amine, followed by the use of NMR coupling constants to assign relative stereochemistries.

Interesting ChemistryBenzyl GroupChemistryCyclopropanationCyclopropane ProductsChimicaInglese
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In the previous post, I investigated the mechanism of cyclopropanation of an enal using a benzylic chloride using a quantum chemistry based procedure. Here I take a look at the NMR spectra of the resulting cyclopropane products, with an evaluation of the original stereochemical assignments.

Interesting ChemistryAmmoniumBenzyl GroupCationsChemical DiagramsChimicaInglese
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Symbiosis between computation and experiment is increasingly evident in pedagogic journals such as J. Chemical Education. Thus an example of original laboratory experiments, that later became twinned with a computational counterpart. So when I spotted this recent lab experiment I felt another twinning approaching.

Interesting ChemistryCarbonChairChemistryConformationChimicaInglese
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Following the general recognition of carbon as being tetrahedrally tetravalent in 1869 (Paterno) and 1874 (Van’t Hoff and Le Bell), an early seminal exploitation of this to the conformation of cyclohexane was by Hermann Sachse in 1890.

Interesting ChemistryAcetic AcidAcidAmideAmineChimicaInglese
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White City is a small area in west london created as an exhibition site in 1908, morphing over the years into an Olympic games venue, a greyhound track, the home nearby of the BBC (British Broadcasting Corporation) and most recently the new western campus for Imperial College London.♣ The first Imperial department to move into […]