318-23 - CH 318 N LECTURE 23 Textbook Assignment Chap 22...

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CH 318 N LECTURE 23 Textbook Assignment: Chap 22. Begin Homework (for credit): POW 12 posted Today’s Topics: Electrophilic Aromatic Substitution Notice & Announcements: Updates posted to notebook Organic Lecture Series 2 Reactions of Reactions of Benzene & Benzene & Its Derivatives Its Derivatives
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Organic Lecture Series 3 -OCH 3 ; examine the meta attack: OCH 3 NO 2 + 3 2 H 3 2 H 3 2 H slow fast -H + + 3 2 + + + (a) (b) (c) Theory of Directing Effects Theory of Directing Effects Nitration of anisole Nitration of anisole Organic Lecture Series 4 -OCH 3 : examine the ortho-para attack: 3 2 + fast + (d) (e) (f) 3 H 2 3 HN O 2 3 H 2 3 H 2 3 2 + + slow + + + (g) : : :: This resonance structure accounts for the selectivity Nitration of anisole Nitration of anisole
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Organic Lecture Series 5 -NO 2 ; examine the meta attack: COOH NO 2 + H 2 H 2 H 2 -H + 2 + slow fast (a) (b) (c) Theory of Directing Effects Theory of Directing Effects Nitration of benzoic acid Nitration of benzoic acid Organic Lecture Series 6 -NO 2 : assume ortho-para attack: 2 + H 2 H 2 H 2 + 2 + (d) (e) (f) The most disfavored contributing structure This resonance structure accounts for the selectivity Nitration of benzoic acid Nitration of benzoic acid
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Organic Lecture Series 7 Activating Activating -Deactivating Deactivating • Any resonance effect Any resonance effect, such as that of - NH 2 , -OH, and -OR, that delocalizes the positive charge on the cation intermediate lowers the activation energy for its formation, and has an activating effect toward further EAS • Any resonance effect Any resonance effect, such as that of - NO 2 , -CN, -CO, and -SO 3 H, that decreases electron density on the ring deactivates the ring toward further EAS Organic Lecture Series 8 • Any inductive effect Any inductive effect, such as that of - CH 3 or other alkyl group, that releases electron density toward the ring activates the ring toward further EAS • Any inductive effect Any inductive effect, such as that of halogen, -NR 3 + , -CCl 3 , or -CF 3 , that decreases electron density on the ring deactivates the ring toward further EAS Activating Activating -Deactivating Deactivating
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Organic Lecture Series 9 ¾ for the halogens halogens , the inductive and resonance effects run counter to each other, but the former is somewhat stronger ¾ the net effect is that halogens are deactivating but ortho-para directing + + + E H Cl H E E + :: : : Deactivating AND o p Directing Deactivating AND o p Directing Inductive effect is slightly dominant Organic Lecture Series 10 Di Di - and and Polysubstitution Polysubstitution Weakly activating Ortho-para Directing Weakly deactivating Moderately activating Strongly activating NH 2 NHR NR 2 OH NHCR NHCAr OR OCAr OCR R F Br I : : : : Strongly deactivating Moderately deactivating CH OO CR COH SO 3 H COR O CNH 2 NO 2 3 + CF 3 CCl 3 Meta Directing CN
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This note was uploaded on 04/20/2009 for the course CH 318N taught by Professor Willson during the Spring '08 term at University of Texas.

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318-23 - CH 318 N LECTURE 23 Textbook Assignment Chap 22...

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