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Henry Rzepa's Blog

Henry Rzepa's Blog
Chemistry with a twist
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GeneralChemical LiteratureDNAEminent MathematicianHelixCiencias QuímicasInglés
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In my blogroll, I link to Tim Gowers’ blog. He is a very eminent mathematician, and so it is interesting to see what motivates him to write a blog about mathematics. This latest post goes a large way to explaining why. He starts by speculating about the features of some piece of research that might render it conventionally unpublishable, highlighting two reasons; (1) it is not original and (2) it does not lead anywhere conclusive.

Interesting ChemistryAnimationCalixareneChiralDielectricCiencias QuímicasInglés
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This story starts with a calixarene, a molecule (suitably adorned with substituents) frequently used as a host to entrap a guest and perchance make the guest do something interesting. Such a calixarene was at the heart of a recent story where an attempt was made to induce it to capture cyclobutadiene in its cavity.

AntarcticBenzeneCyclohexaneDispersion InteractionsMelting PointsCiencias QuímicasInglés
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One of the delights of wandering around an undergraduate chemistry laboratory is discussing the unexpected, if not the outright impossible, with students. The >100% yield in a reaction is an example. This is sometimes encountered (albeit only briefly) when students attempt to recrystallise a product from cyclohexane, and get an abundant crop of crystals when they put their solution into an ice-bath to induce the crystallisation.

Interesting ChemistryBijvoetChemistChiropticalD(CGCG)Ciencias QuímicasInglés
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Science is about making connections. Plenty are on show in Watson and Crick’s famous 1953 article on the structure of DNA[cite]10.1038/171737a0[/cite] but often with the tersest of explanations. Take for example their statement “ Both chains follow right-handed helices ”. Where did that come from?

Interesting ChemistryRainer HergesTutorTutorial MaterialCiencias QuímicasInglés
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Is there a preferred pack size for electrons on the move? Or put less flamboyantly, is there an optimum, and a maximum number of arrows (electron pairs) that one might push in revealing the mechanism of a concerted reaction? A sort of village-instinct for electrons.

Chemical IT3D GraphicsAppleGPUHTML5Ciencias QuímicasInglés
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If you get a small rotatable molecule below, then ChemDoodle/HTML5/WebGL is working. Why might this be important? Well, the future is mobile, in other words, devices that rely on batteries or other sources of built-in power. This means the power guzzling GPU cards of the past (some reach ~400 Watts!) cannot be used.

General/RTAnomeric EffectsArrow PushingConfigurational IsomerCiencias QuímicasInglés
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Chemistry gets complex very rapidly. Consider the formula CH 3 NO as the topic for a tutorial in introductory chemistry. I challenge my group (of about 8 students) to draw as many different molecules as they can using exactly those atoms. I imply that perhaps each of them might find a different structure; this normally brings disbelieving expressions to their faces.

HypervalencyInteresting ChemistryHenry RzepaJahn-TellerPenceCiencias QuímicasInglés
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Do you fancy a story going from simplicity to complexity, if not absurdity, in three easy steps? Read on! The following problem appears in one of our (past) examination questions in introductory organic chemistry. From relatively mundane beginnings, one can rapidly find oneself in very unexpected territory. How would one make 3-nitrobenzonitrile?

Interesting ChemistryActivation Free EnergyBenzonitrile ProductChemical MythologyColoured SolutionsCiencias QuímicasInglés
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Janus was the mythological Roman god depicted as having two heads facing opposite directions, looking simultaneously into the past and the future. Some of the most ancient ( i.e. 19th century) known reactions can be considered part of a chemical mythology; perhaps it is time for a Janus-like look into their future. Reaction of the diazonium cation with cyanide.