Click here for a copy of the mechanism sheet used in lecture today.
A. Tips for test preparation; what you need to know
Know the mechanisms, and understand how each step makes sense. BE ABLE TO IDENTIFY EACH STEP IN EACH MECHANISM AS ONE OF THE FOUR MECHANISTIC ELEMENTS (add a proton, take away a proton, attack with a nucleophile and lose a leaving group).
Know all the KRE's (Key Recognition Elements) for the different reactions, concentrating on the C-C bond-forming reactions
Know how to use the pKa table!
Be able to use all the reactions in the roadmap you have made
B. Tips for test preparation; what you should do to prepare
By yourself:
Master the reactions, mechanisms, KRE's, and analyze the homework and old exam answers. KNOW YOUR STUFF!
Make a sheet that lists the PRODUCTS of all the reactions first, then fill in the starting materials
With study partners:
Make up problems for each other in which you derive a product of a reaction. Show your study partner the products, and have them deduce the starting materials and reagents.
Make up synthesis problems for each other, by running a series of reactions on a randomly chosen starting material. Show your study partners the final product and the starting material, and have them fill in the rest.
Rules of the Day 3-26-08
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. Aldols between two different aldehydes can be run in high yield if one of the carbonyls is a ketone and the other is an aldehyde that cannot make an enolate. This is generally only relevant to formaldehyde and benzaldehyde.
3. LDA is a wicked strong base that is not nucleophilic. It will quantitatively convert a carbonyl species into an enolate, so it can be used for crossed aldol or Claisen reactions. The amount you add matters!! You need to add 1.0 equivalent of LDA to make 1.0 equivalent of enolate from an ester or aldehyde.
4. 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.
Homework: Begin studying for next week's midterm! Read: No new reading Problems: No new problems
