Conformational dynamics and strain · Conformational dynamics and strain Johannes Wislicenus...
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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
Transcript of Conformational dynamics and strain · Conformational dynamics and strain Johannes Wislicenus...
Conformational dynamics and strainJohannes 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 ringsDye synthesis
Nobel Prize 1905Pics: Wikipedia
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)
Cyclohexane as a chair?
1918:structural prooffor the “chair” …
diamond!
Odd Hassel(1897-1981)
Determined cyclohexanestructure and fluxionalityPublished in Norwegian
Sir Derek Barton(1918-1998)
ConformationalAnalysis
He read the Scandinavian lit!
Shared the 1969 Nobel Prize
Pics: Wikipedia
Fused rings – decalin system: cortisone
Thank you Google image search
Stereoisomerism proposals 1874
Joseph Achille Le Bel1847-1930(France)
Jacobus Henricus van’t Hoff1852-1911
(The Netherlands)“La chimie dans l’espace”
First Nobel Prize
Pics: Wikipedia
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
Chiral discrimination
Jones, Organic
Chemistry2nd ed.
Fig. 4.26
Importance of chirality
Smell: R-carvone:spearmint
S-carvone:caraway
Toxicity of a morningsickness
drug:
Harmless to fetus Teratogen: limb defects
“Therapeutics:”
Vick’s inhaler meth
Cahn-Ingold-Prelog 1950-1955
Sir Christopher K. Ingold1893-1970
Reaction mechanisms
Vladimir Prelog1906-1998
Nobel Prize 1975
Robert Sidney Cahn1899-1981
(R-S naming from R.S.?)
Pics: Wikipedia
