Topic 37: Reaction at the alpha carbon: enols and enolates

37.1What is an enol?
 
37.2What is an enolate?
 
37.3How many times more acidic is 2,4-pentanedione than 2-pentanone?
 
37.4How might that be relevant to this discussion?
 
37.5Tautomerization can be catalyzed either by acid or base. What is the mechanism of tautomerization in each case?
 
37.6What other compounds, besides ketones and aldehydes, can be deprotonated to form enolate-like species?
 
37.7What is the most common base used to make enolates?
 
37.8Why is it better than hydroxide?
 
37.9Why is it better than MeLi?
 
37.10What does LDA stand for? Structure?
 
37.11Why might it be most common to use LDA at such a low temperature as −78 C?
 
37.12What is the difference between kinetic and thermodynamic control?
 
37.13What is the general way to make a “kinetic” enolate?
 
37.14The standard way to equilibrate a pair of enolates is to deprotonate the ketone with LDA at −78 C using slightly less than one equivalent of base and then to just let the reaction warm up to room temperature. Why would it be important to have just a little bit of unreacted ketone present when this warming occurs? How does that accomplish equilibration?
 
37.15Why/when would it be important to not expose a ketone to strong acid or strong base?
 
37.16How could this process work in your favor, if you were a synthetic organic chemist?
 
16 questions
472 questions for Organic II

472 Questions for Organic II

Dearest Student. This web page is a set of questions I call Detailed Intended Learning Outcomes For Organic Chemistry (Part II). Some time ago I asked myself, "Bob, what do you think are the key questions that you hope students will be able to answer after taking Chemistry 248 at St. Olaf College?" So here you have them. Some are very simple; some require more thought. All are good questions to be thinking about as you read, discuss, and master the practical aspects of organic chemistry. They are discussion starters and review tips. There are no answers here (though there are some clues). The questions are here to help you focus on what's important (to me, at least!) and organize your learning process. The questions are grouped into topics. Bite-size chunks. Take them a few at a time. Don't feast on them all at one sitting!

(preliminary version 2021.01.15 feeback: Bob Hanson)