Unformatted text preview: of re activity Cyclohexatriene is Special Benzene Benzene C yclic array of six e ctrons has spe stability, calle cial d six le arom aticity (C hapte 15). r arom Be neis re nze lative ine to H2-cat, e ctrophile oxidants, in ly rt s, -cat, le com parison with he xatrie . ne com Extended Conjugation in Natural and Unnatural Products Unnatural Orangecolor of carrots Biological Biological de gradation de Vision Organic Conductors Organic ~Ag Heeger, MacDiarmid, Shirakawa, Nobel Prize 2000 (based on discoveries made in 1970, 1976) Light e itting diode (LEDs) s Light m Conjugated Systems Undergo Special Transformations: Pericyclic Reactions Pericyclic
Theconjugate π syste can re as a unit, involving both d m act The e . For e ple nds xam , 1. C ycloadditions: TheDiels-Alder reaction, a [4+2] The
HC HC CH 2 CH 2 CH 2 +
CH 2 Δ
20% HC HC H2 C CH 2 CH 2
Otto Die ls 1876-1954 Kurt Alde r 1902-1958 4π-4C -4C Die ne Die 2π-2C -2C Die nophile Die C H2 Nobe Prize1950 l C ycloadduct The Diels-Alder Reaction is The Chemoselective Chemoselective
Die ls-Alde re r actions work be whe wepair an st n Die e -rich (push) die with an e -poor (pull) die nophile , (push) ne die or an e -poor die with an e ne -rich die nophile De nds on substitue pe nts: e -Donating: Alkyl, alkoxy, alkylthio Alkyl
3 3 3 2 Hype rconjugation C, H Re sonance COCH 3 H O, COCH 3 S OCH 3 HC H Eve though O is e gative(inductivee ct), resonance wins out. n -ne ffe resonance Eve O e -Wit...
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This note was uploaded on 09/04/2010 for the course CHEM 10966 taught by Professor Vollhardt during the Spring '10 term at Berkeley.
- Spring '10