Click here for a copy of the mechanism sheet used in lecture today.
Rules of the Day 3-28-08
1. There are four new concepts associated with chapter 19. Click on these one at a time to get more information.
C) Beta-Dicarbonyl species are especially acidic
D) Conjugate addition to alpha,beta unsaturated carbonyl species.
2. The acetoacetate synthesis provides a simple way to make complex methyl ketones. The enolate is formed using 1.0 equivalent of strong base such as NaOEt, followed by 1) alkylation with an alkyl halide, 2) acid catalyzed hydrolysis of the ester and heating (loss of CO2). The initial acetoacetate can actually be alkylated twice if necessary.
3. A methyl ketone is the synthesis key recognition element (KRE) for synthesis by the acetoacetate synthesis.
4. The malonic ester synthesis is entirely analogous to the acetoacetate synthesis, except diethyl malonate is used and a substituted carboxylic acid derivative is the ultimate product following ester hydrolysis in acid (H3O+) and heating (loss of CO2).
5. A derivitized carboxylic acid function is the synthesis key recognition element (KRE) of the malonic ester synthesis. These can be tough to spot so practice.
6. An enamine ("aka mini me") is formed when a secondary amine reacts with a ketone or aldehyde. The enamine can be thought of as the resonance hybrid of two contributing structures. The b-carbon atom is nucleophilic entirely analogous to an enolate. (Yes, you guessed it, "mini me" reacts as a nucleophile like Dr. Evil! Seriously folks, I don't make this stuff up).
7. Enamines can be alkylated by reaction with alkyl halides, or acylated by reaction with acid chlorides.
Homework: There is no homework to turn in next week because I want you to concentrate on doing the following homework over this weekend. These are great problems, on the challenging side, and there is no need to make more for you to do. PLEASE DO THE READING AND THESE PROBLEMS EVEN THOUGH YOU DO NOT NEED TO TURN THEM IN!!! Read: 19.6-19.8A, all of Chapter 20 Problems 19.7-19.15, 19.41, 19.45, 19.48, 19.52, 19.53, 19.55, 19.57 (Great one!)
