N an at rm ics wave ngth de nde can go e r le pe nt

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Unformatted text preview: dothe (C Cbe r than C C tte , and no ring strain pre nt) se hυ Im e ml Electrocyclic Reactions are Stereospecific Stereospecific Δ CH 3 Only! cis–3,4-Dim thylcyclobute e ne CH 3 CH 3 cis,trans–2,4-He xadie ne Δ Only! Trans CH 3 Trans,trans Movement of Substituents Movement C onrotatory: sam dire e ction sam CH 3 CH 3 Both e r Both ithe clockwiseor counte rclockwise S e : am product. product. The rotatein the y H C onrotatory H CH 3 H CH 3 Δ H Im e ml CH 3 H CH 3 H C onrotatory (clockwise ) (clockwise CH3 H H3 C H Δ C ounte rclockwiseconrotation in principlepossiblebut ste rically prohibite : d ste CH3 H CH 3 H Δ H H CH 3 CH 3 Fascinatingly, hυ goe disrotatory (rotation s disrotatory in oppositedire opposite ctions) CH 3 CH 3 hυ dis CH 3 CH 3 Ring closure CH 3 Ring ope ning CH 3 CH 3 hυ dis CH 3 Eve m startling: Thehe n xatrie /cyclohe ne xadie inte ne rconve rsion is Eve ore also ste ospe re cific, but follows theoppositerule of se of rotation, nse ste opposite s com d to thebutadie /cyclobute syste : pare ne ne m com Δ = dis dis Im e ml hυ = con con Robe B. Woodward rt Robe 1917-1979 Roald Hoffm ann b. 1937; NP 1981...
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