Rules of the Day 320N

1. In summary, you can make any of the less reactive carboxylic acid derivatives directly from any of the more reactive carboxylic acid derivatives by using the appropriate nucleophiles and reaction conditions.

2. However, you can make a more reactive carboxylic acid derivative from a less reactive carboxylic acid derivative if you first hydrolyze the less reactive carboxylic acid derivative to the carboxylic acid, then use SOCl2 to make the acid chloride, that, in turn, can make any of the other carboxylic acid derivatives.

3. The general features of carbonyl reaction mechanisms can be related to the plot for the first Star Wars movie starring Nuc "the nucleophile" Skywalker, Old "Pi Bond" Kinobe, Han "the proton" Solo, and their faithful robots sp3O and SN2E2.

4. It is important that you are able to write a balanced equation for each mechanism that we cover. To do this, keep track of all the atoms in all of the products produced during a reaction mechanism and balance that on the starting materials side of the equation. This will help you keep track of "acid or base catalyzed" vs. "acid or base promoted" as well as EQUIVALENTS. Doing this establishes a critical link between reaction mechanisms and how to use them properly in synthesis reactions!There are four new concepts associated with chapter 19. Click on these one at a time to get more information. We only covered the first two in today's lecture.

A) Reactions favor the formation of weaker bases at equilibrium (provides a motive), so you need to have a Table of pKa values

B) Enolates as nucleophiles

C) Beta-Dicarbonyl species are especially acidic

D) Conjugate addition to alpha,beta unsaturated carbonyl species.

5. The C atom next to a carbonyl is called the apha carbon, and a carbon atom two carbon atoms away is called the beta carbon. H atoms attached to the alpha carbon are called alpha hydrogens, and H atoms attached to the beta carbon are called beta hydrogens.

6. Important acid-base concepts to remember are that 1) acid-base reactions favor formation of the weaker acid/weaker base (quantitatively, the equilibrium constant can be derived from the difference of the pKa values of the acids), 2) Weaker conjugate bases are derived from stronger acids and vice versa, and 3) stronger acids have lower pKa values. Putting 2) and 3) together means that conjugate bases of acids with lower pKa values are favored at equilibrium.

7. Enolates are stabilized by a combination of delocalization of charge and formation of a pi-way. By far the most important reactions of enolates are with carbonyl groups to make carbon-carbon bonds.

8. When a catalytic amount of base is added to an aldehyde, the enolate that is formed reacts with an aldehyde carbonyl via mechanism A to create a new carbon-carbon bond. The reaction is called the aldol reaction. See how the concept of enolates was ripped of in an old popular movie staring Mike Myers. Often, two new chiral centers are created in an aldol reaction, meaning racemic mixtures of two pairs of enantiomers are created. Aldol reactions run using catalytic base are favored for aldehydes, but not ketones.

Homework:

Read: Sections 19.1-19.3 in the ebook textbook. This text is part of the Longhorn Textbook access program.

Take the Daily Quiz 11 before 10 PM tomorrow. Click here to access the quiz. These quizzes are designed to review the important material from today's lecture.

Finish working on Homework 5, that will be due tonight, February 25 at 10 PM. There are both Aktiv learning and Gradescope problem sets.

Click here to get the Aktiv Homework Problem Set 5

Click here for the Gradescope Homework Problem Set 5

To submit your homework log onto "Gradescope" on the menu bar of the class Canvas page, or you can Click here to get there directly.

Start working on Homework 6 that will be due Wednesday, March 4th at 10 PM. There are both Aktiv learning and Gradescope problem sets.

Click here to get the Aktiv Homework Problem Set 6

Click here for the Gradescope Homework Problem Set 6