Rules of the Day
3-9-2026
Click here for a copy of the lectures notes I wrote in class
Click here for a copy of the handouts I used in class today
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.
1. The mechanism of the Michael reaction involves attack by the enolate at the beta-carbon atom to generate a new enolate intermediate, that is reprotonated during the reaction to give an enol, that tautomerizes to the keto form. If a beta-dicarbonyl species is used, then the final step is deprotonation at the remaining alpha hydrogen. In this case, the chemist opens up the flask and adds mild acid to give the final product.
2. The key recognition element of the Michael reaction is a carbonyl with a nucleophile derived from an enolate (usually a beta-dicarbonyl enolate) attached to the beta-carbon atom. These can be tough to spot so practice.
3. The alpha,beta-unsaturated carbonyl species can be an aldehyde, ketone, ester, or amide .
4. The nucleophile is generally an enolate derived fom a beta-dicarbonyl species, but enamines and amines work as well.
5. The Michael reaction is favored by both motive (C=O stronger than C=C) and opportunity (enolate intermediate that has a delocalized charge and a pi-way compared to a localize O-).
6. When there are several possible enolates in a molecule with two aldehydes/ketones, the product will be the most stable ring (5 or 6 membered ring).
7. The Robinson annulation is a Michael reaction followed by an aldol reaction to make a six-membered ring, ending with a dehydration. Talk about a basketball reaction!!! This reaction is important because it helps make steroid rings, and steriods are important pharmaceuticals; hormones such as birth control pills and corticosteroids such as prednisone are steroids.
Click here to see a "Things you need to know" handout that explains "equivalents" in more detail.
If you are having even a little trouble with mechanisms: Print out multiple copies of the new Mechanism Sheet 18 Microscopic Reversibility. Practice writing arrows and reagents in both directions (Acid catalyzed ester hydrolysis, starting at the top then working down and Fischer esterification, starting at the bottom then working up), taking advantage of the common structures drawn in red. Try to UNDERSTAND why each step occurs and why acid catalyzed ester hydrolysis uses water or H3O+ in several steps while Fischer Esterification used an alcohol or protonated alcohol. Do this several times until it makes sense. Then print out several copies of the Fischer esterification and acid catalyzed ester hydrolysis sheets and work them until it all makes sense. Keep asking yourself why each step occurs as it does (add a proton, make a bond etc.) until you understand why every step is the best choice. Compare your answers to the sheets you filled out in class.
If you are having even a little trouble with synthesis questions: You must know all the reactions, full stop. After you know your reactions very well, you need to learn the KRE's. The best way to learn these is to turn it into a game. Find some friends and get a list of all the reactions we have learned this semester. Each of you needs to write down an example of each reaction we have learned, with the product on a separate sheet of paper. For example, write an n-butyl Grignard reacting with 2-pentanone and put the product on a separate sheet. Make up examples of each reaction. Then give the product sheet to your friends and have them write down possible reactions that gave the products. There are often several ways to make the same product by the way. Do this for an hour and you will know your KRE's. When working synthesis problems, work backwards. Count carbons in products vs. reactants to identify where new C-C bonds are formed. When you know where the new C-C bonds are formed you can identify KRE's. Be systematic and you will get these.
Homework:
There are no quizzes during exam weeks.
Looking ahead to the second midterm this week, here are some practice problems. You will not turn these in, but I have posted answers for you to check.
There is no Aktive Homework 7.
Because of all that is going on, there is a Homework 7, but you will not turn it in this week. It is desigened to help you get ready for the midterm. We have posted both the questions and answers to help you prepare.