Chemistry 125 Lecture 70 April 19 2010 Acyl

Chemistry 125: Lecture 70 April 19, 2010 Acyl Compounds (Ch. 18) -H Reactivity This (Ch. 19) For copyright notice see final page of this file

Fischer Esterification (sec. 17. 7 a) + starts with + addition O H + substitution R C OR O H + RO H Tetrahedral Intermediate at C (A/D, not pentavalent transition state)

Victor Meyer (1848 - 1897) Victor Meyer 9/8/48 - 8/8/97 “Geliebte Frau! Geliebte Kinder! Lebt wohl! Meine Nerven sind zerstört; ich kann nicht mehr. ” introduced the idea of Steric Hindrance (1894) “…the source of this behavior is stereochemical…the space filling of the neighboring groups” Configuration van’t Hoff (1874) Conformation Sachse (1891)

Fischer Esterification Didn’t Work with 2, 6 -Dimethylbenzoic Acid Carboxylic Acid Tetrahedral Intermediate STRAIN!

Melvin Newman’s Method Fischer Esterification (sec. 20. 8, p. (1941) 965) Linear Tetrahedral Acylium Intermediate (D/A, (A/D) like SN 1) + + H O + R C +O O HH+ + OR + + Pour into ROH HH OH 100% H SO H R substitution at C (attaching second H+ inhibits reversal) sometimes 2 4

Acyl Derivatives from Ketene sec. 18. 11, p. 907 H 2 C=C=O Nu:

Baeyer-Villiger Reaction (insert O) pp. 907 -909 Remember Ph. CHO + O 2 H- migration R- migration

Migration from Acyl Carbon + R C R O inserts X between R and C=O X L

Beckmann Rearrangement (insert N) pp. 909 -911 inserts in anti bond

Beckmann Rearrangement (insert N) pp. 909 -911 R- migration in cation

Arndt-Eistert Reaction (insert C) pp. 915 -917 Wolff elongates acid by one carbon Rearrangement R- migration

Acidity Tables 19. 1 (p. 933), 19. 2 (p. 943), 19. 3 (p. 958) H p. Ka ~ 18

LDA hindered strong base (p. Ka = 36) (p. 944) p. Ka ~ 25 K ~ 1011 complete formation of enolate not just a little at equilibrium (slow attack on C=O, none on enolate)

Acid & Base H/D Exchange via enol and enolate (sec. 19. 2 a)

Racemization via enol and enolate (sec. 19. 3)

-Halogenation ketones/aldehydes (19. 4 a) Iodoform with base +

-Halogenation carboxylic acids (19. 4 b) Hell-Volhard-Zelinsky

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