Chemistry 125: Lecture 70 April 19, 2010 Acyl

Chemistry 125: Lecture 70 April 19, 2010 Acyl

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

page of this file Fischer Esterification (sec. 17.7a) + starts with addition +

O H + R C OR O H + RO TetrahedralH

Intermediate substitution at C (A/D, not pentavalent transition state) Victor Meyer (1848 -H Reactivity 1897) Victor Meyer 9/8/48 -H Reactivity 8/8/97 Geliebte Frau! Geliebte Kinder! Lebt wohl! Meine Nerven sind zerstrt; ich kann nicht mehr.

introduced the idea of Steric Hindrance (1894) the source of this behavior is stereochemicalthe space filling of the neighboring groups Configuration vant Hoff (1874) Conformation

Sachse (1891) Fischer Esterification Didnt Work with 2,6-H ReactivityDimethylbenzoic Acid Carboxylic Acid Tetrahedral Intermediate STRAIN! Melvin Newmans

Method Fischer Esterification (sec. 20.8, p. (1941) 965) Tetrahedral Intermediate Linear Acylium Intermediate (D/A,(A/D) like SN1)

+ 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 H2C=C=O Nu:

Baeyer-H ReactivityVilliger Reaction (insert O) pp. 907-H Reactivity909 Remember PhCHO + O2 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-H Reactivity911

inserts in anti bond Beckmann Rearrangement (insert N) pp. 909-H Reactivity911 R- migration in cation Arndt-H ReactivityEistert Reaction (insert C) pp. 915-H Reactivity917

Wolff elongates acid by one carbon Rearrangement R migration Acidity Tables 19.1 (p. 933), 19.2 (p. 943), 19.3 (p. 958) H pKa ~ 18

LDA hindered strong base (pKa = 36) (p. 944) pKa ~ 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. 19.2a) Racemization via enol and enolate (sec. 19.3) -H ReactivityHalogenation ketones/aldehydes (19.4a) Iodoform with base +

-H ReactivityHalogenation carboxylic acids (19.4b) Hell-H ReactivityVolhard-H ReactivityZelinsky End of Lecture 70 April 19, 2010 Copyright J. M. McBride 2010. Some rights reserved. Except for cited third-party materials, and those used by visiting speakers, all content is licensed under a Creative Commons License (Attribution-NonCommercial-ShareAlike 3.0). Use of this content constitutes your acceptance of the noted license and the terms and conditions of use. Materials from Wikimedia Commons are denoted by the symbol

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