Rules of the Day
3-26-2024
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.
Homework:
Read: Sections 19.8 - 19.9 in the ebook textbook. This text is part of the Longhorn Textbook access program.
Take the Daily Quiz 15 before 10 PM tomorrow. Click here to access the quiz.
Start working on the Homework Problem Set 8, due at 10 PM on Monday, April 7. Click here to access the Homework Problem Set 8. This IS AN IMPORTANT ONE!! We will be grade it for completion only. There is no Aktiv learning portion of this homework, just Gradescope.