Lect23_1014 - the green hydrogen is anti to the chlorine...

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Ch. 7 - 1 The 5 atoms involved in the transition state of an E2 reaction (including the base) must lie in the same plane The anti coplanar conformation is the preferred transition state geometry The anti coplanar transition state is staggered (and therefore of lower energy), while the syn coplanar transition state is eclipsed 6C. 6C. The Stereochemistry of E2 The Stereochemistry of E2 Reactions Reactions
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Ch. 7 - 2 Mechanism for an E2 Reaction Mechanism for an E2 Reaction 3 3 3 β α EtO removes a proton; C H breaks; new bond forms and Br begins to depart Partial bonds in the transition state: C H and C Br bonds break, new C C bond forms C=C is fully formed and the other products are EtOH and Br
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Ch. 7 - 3 E2 elimination where the only axial β hydrogen is from a less stable Conformer Menthyl chloride (more stable conformer) Elimination is not possible for this conformation because no hydrogen is anti to the leaving group Menthyl chloride (less stable conformer) Elimination is possible for this conformation because
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Unformatted text preview: the green hydrogen is anti to the chlorine Ch. 7 - 4 CH(CH 3 ) 2 H H H Cl H CH 3 H 3 C CH(CH 3 ) 2 CH(CH 3 ) 2 H H H Cl H CH 3 OEt The transition state for the E2 elimination is anticoplanar 2-Menthene (100%) Ch. 7 - 5 7. Acid-Catalyzed Dehydration of Alcohols Most alcohols undergo dehydration (lose a molecule of water) to form an alkene when heated with a strong acid Ch. 7 - 6 The relative ease with which alcohols will undergo dehydration is in the following order: Ch. 7 - 7 7B. 7B. Carbocation Carbocation Stability & the Stability & the Transition State Transition State Ch. 7 - 8 8. Carbocation Stability & Occurrence of Molecular Rearrangements 8A. 8A. Rearrangements during Rearrangements during Dehydration of Secondary Alcohols Dehydration of Secondary Alcohols Ch. 7 - 9 Migration of a methanide o 3 3 3 3 o 3 3 3 3 Ch. 7 - 10 8B. 8B. Rearrangement after Dehydration Rearrangement after Dehydration of a Primary Alcohol of a Primary Alcohol...
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Lect23_1014 - the green hydrogen is anti to the chlorine...

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