CHEM 3332 1st Edition Lecture 16Outline of Last Lecture Substituents as Activators/DeactivatorsHow do substituents affect reactivity?An electron releasing substituent:An electron withdrawing substituentThe electron withdrawl takes place in two ways:I. Inductive: differences in the electronegativities of the atoms-CH3-CLII. Resonance:Activator:Deactivator:Substituents as Directors:Meta Directors:Ortho ResultPara ResultMeta ResultOrtho/Para Directors:Orto Result:Para Result:Meta Result:The Special Case of the Halogens:Deactivating:Orth/Para Directing:Examples:1.2.3.Synthetic Applications:Orientation in Disubstituted BenzenesI. The “No Brainer” Case:II. A Bigger ChallengeIII. The Biggest Challenge:Examples: Outline of Current Lecture Nucleophilic Aromatic Substitution of Aryl HalidesThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.-No Sn2 on sp2!!! )or SN1 either!)Two pathways:I. Addition/Elimination Mechanism: takes place if strong electron withdrawing (deactivating) groups are ortho and/or para to the halide; the more deactivators, the faster the reaction rateNu=Addition:Elimination:II. Elimination/ Addition- takes place when there are NO strong electron withdrawing )deactivating) groups ortho or para to the halide; requires harsh conditionsNu=Mechanism:Elimination:Addition:Birch Reduction of Substituted Benzenes:-electron withdrawing groups activate a carbon for reduction because the carbanion stabilized-electron donating groups deactivate a carbon for reduction because the carbanion is destabilizedExamples:1.2.3.Side Chain of Reactions of Benzene DerivativesI. Oxidation- the benzene ring and the bond to the first carbon of a side chain can survive harsh oxidizing conditions1.2.3.Evidence for Benzene Existence:Add furan to reaction mixture:Addition Reactions of BenzeneI. Chlorination of BenzeneII. Catalytic HydrogenationIII. Birch Reduction dissolving metal reductionMechanism Current
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