1 ELECTROPHILIC SPECIES IN EAS. 2 Summary of Directing Effects FOUR CATEGORIES: I. Strongly activating, ortho/para directing (LP electrons) (eg. -OMe,

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Sigma Complex Intermediate is more stable if nitration occurs at the ortho or para position. =>

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Presentation transcript:

1 ELECTROPHILIC SPECIES IN EAS

2 Summary of Directing Effects FOUR CATEGORIES: I. Strongly activating, ortho/para directing (LP electrons) (eg. -OMe, Inductive and Resonance effects) I. Strongly activating, ortho/para-directing (eg. –OMe, I, R) II. Weakly activating, ortho/ para-directing (eg. –C H 3 I) III. Weakly deactivating, ortho/ para-directing (eg. –CI, I, R) IV. Deactivating, meta-directing (eg. -N O 2, I)

3 I. Strongly activating, ortho/para directing (eg. -OMe, inductive, resonance) Reaction Coordinate II. Weakly activating, ortho/para directing (eg. -CH 3 inductive)

4 Stability of Sigma Complex Defines Outcome II. Weakly activating, ortho/para directing (eg. -CH 3 inductive) Intermediate is more stable if nitr atior occurs at the ortho or para position.

5 III. Weakly deactivating, ortho/para directing (eg. -Cl, Inductive/Resonance) Chlorobenzene III. Weakly deactivating, ortho/para directing (eg. -Cl, Inductive/Resonance)

6 IV. Deactivating, meta directing (eg. -NO 2, inductive) IV. Deactivating, meta directing (eg. -NO 2, inductive) Positive or partial positive charge on substituent very unfavorable in σcomplex.

7 SYNTHETIC STRATEGIES WITH AROMATIC COMPOUNDS Steric Effects in Electrophllic Aromatic Substitution

8 STERIC EFFECTS IN ELECTROPHILIC AROMATIC SUBSTITUTION Reaction with Br 2 /FeBr 3 to afford monobrominated derivative Statistically 66%ortho/33%para)