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Henry Rzepa's Blog

Henry Rzepa's Blog
Chemistry with a twist
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Chemical ITCrystal_structure_miningAlkane StereochemistryAnomeric EffectCarbohydrate ChemistryChemieEnglisch
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The anomeric effect is best known in sugars, occuring in sub-structures such as RO-C-OR. Its origins relate to how the lone pairs on each oxygen atom align with the adjacent C-O bonds. When the alignment is 180°, one oxygen lone pair can donate into the C-O σ* empty orbital and a stabilisation occurs.

Chemical ITCrystal_structure_miningChemical BondingChemical NomenclatureHammett EquationChemieEnglisch
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Previously, I showed how conjugation in dienes and diaryls can be visualised by inspecting bond lengths as a function of torsions. Here is another illustration, this time of the mesomeric resonance on a benzene ring induced by an electron donating substituent (an amino group) or an electron withdrawing substituent (cyano).

Chemical ITGeneral10.15200143871.12809AcademiaChemieEnglisch
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I recently received two emails each with a subject line new approaches to research reporting. The traditional 350 year-old model of the (scientific) journal is undergoing upheavals at the moment with the introduction of APCs (article processing charges), a refereeing crisis and much more. Some argue that brand new thinking is now required.

Chemical ITCrystal_structure_miningInteresting ChemistryCarbonCationsChemieEnglisch
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I recently followed this bloggers trail; link1 → link2 to arrive at this delightful short commentary on atom-atom bonds in crystals by Jack Dunitz. Here he discusses that age-old question (to chemists), what is a bond? Even almost 100 years after Gilbert Lewis’ famous analysis, we continue to ponder this question.

Reaction MechanismActivation Free EnergyBasis SetDan SingletonEnergy DifferencesChemieEnglisch
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Previously on the kinetic isotope effects for the Baeyer-Villiger reaction, I was discussing whether a realistic computed model could be constructed for the mechanism. The measured KIE or kinetic isotope effects (along with the approximate rate of the reaction) were to be our reality check.

Interesting ChemistryChemieEnglisch
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Peter Edwards has just given the 2015 Hofmann lecture here at Imperial on the topic of solvated electrons. An organic chemist knows this species as “e–” and it occurs in ionic compounds known as electrides; chloride = the negative anion of a chlorine atom, hence electride = the negative anion of an electron.