Conformational dynamics and strain Johannes Wislicenus 1835-1902 - - PowerPoint PPT Presentation

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Mar 09, 2023 300 likes •423 views

Conformational dynamics and strain Johannes Wislicenus 1835-1902 "specially directed forces, the affinity-energies are responsible for torsional motions in a molecule (vibrational, rotational, angular ) Need not think about

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Conformational dynamics and strain

Johannes Wislicenus 1835-1902 "specially directed forces, the affinity-energies” are responsible for torsional motions in a molecule (vibrational, rotational, angular …) Need not think about molecules as static in 2D! Ring strain … aka angle strain … aka Baeyer strain Adolf von Baeyer (1853-1917) Recognized the strain that must be present in small rings Dye synthesis Nobel Prize 1905 Pics: Wikipedia

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Cyclohexane as a chair?

Herman Sachse 1890 Realized cyclohexane need not be planar, Conformational isomers would alleviate strain! (At left, Hernán Sachse) Sachse’s problem: Organic chemists don’t math so good.

Zeitschrift für physicalische chemie, 10, 201-241 (1892)

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Cyclohexane as a chair?

1918: structural proof for the “chair” … diamond!

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Odd Hassel (1897-1981) Determined cyclohexane structure and fluxionality Published in Norwegian Sir Derek Barton (1918-1998) Conformational Analysis He read the Scandinavian lit! Shared the 1969 Nobel Prize Pics: Wikipedia

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Fused rings – decalin system: cortisone

Thank you Google image search

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Stereoisomerism proposals 1874

Joseph Achille Le Bel 1847-1930 (France) Jacobus Henricus van’t Hoff 1852-1911 (The Netherlands) “La chimie dans l’espace” First Nobel Prize Pics: Wikipedia

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Manuscript reviews: ca. 1874

"A Dr. J. H. van ’t Hoff of the Veterinary School at Utrecht has no liking, apparently, for exact chemical investigation. He has considered it more convenient to mount Pegasus (apparently borrowed from the Veterinary School) and to proclaim in his ‘La chimie dans l’espace’ how, in his bold flight to the top of the chemical Parnassus, the atoms appeared to him to be arranged in cosmic space."

Hermann Kolbe, senior editor of the Journal für Praktische Chemie

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Chiral discrimination

Jones, Organic Chemistry 2nd ed.

Fig. 4.26

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Importance of chirality

Smell: R-carvone: spearmint S-carvone: caraway Toxicity of a morning sickness drug: Harmless to fetus Teratogen: limb defects “Therapeutics:” Vick’s inhaler meth

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Cahn-Ingold-Prelog 1950-1955

Sir Christopher K. Ingold 1893-1970 Reaction mechanisms Vladimir Prelog 1906-1998 Nobel Prize 1975 Robert Sidney Cahn 1899-1981 (R-S naming from R.S.?) Pics: Wikipedia