Rules of the Day 3-07-07

Click here for today's lecture mechanism sheet 1

Click here for today's lecture mechanism sheet 2

1. Acid chlorides, anhydrides, and esters react with amines involving an initial attack to create a zwitterionic tetrahedral intermediate, followed by a proton transfer, followed by loss of the leaving group to give the amide.

2. The key issue that distinguishes the different carboxylic acid derivative mechanisms is proton transfers, as they all involve mechanism B or a variation there of with proton transfers occuring at different times. These are best understood, not memorized, using the following priciples:

A. Strong nucleophiles attack carbonyls without acid catalysis.

B. Reaction of less reactive carboxylic acid derivatives with weak nucleophiles requires protonation of the carbonyl.

C. Nucleophiles that are uncharged must be deprotonated after attacking the carbonyl group.

D. Poor leaving groups need to be protonated before they leave.

E. Proton transfer is a term used to describe movement of a proton from one positively charged atom on a molecule, to another negatively charged atom of the same molecule. It may actually involves two different steps (related to points C. and D. above).

F. Reactions in acid generally have all neutral or positively charged intermediates.

G. Reactions in base or using a negatively charged nucleophile generally have all neutral or negatively charged intermediates.

3. It looks as thought the plot for the Star Wars movies is really derived from carbonyl chemistry.

4. You can make less reactive carboxylic acid derivatives from more reactive ones.

Homework: Start Working on Homework Problem Set 7. It will be due before class on Wednesday, March 21. Reading: Sections No new reading Problems in Book: 18.24, 18.25, 18.27, 18.32 You will not turn these in but they are very helpful to PREPARE for the next lecture.