Rules of the Day
2-6-2024
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
Featured Golden Rule of Chemistry: 9. Functional groups react the same in different molecules.
1. Mammalian vision is the result of a photon being absorbed by a molecule called 11-cis-retinal, converting the cis C=C to a trans C=C, resulting a signal being sent to the brain. 11-Cis-retinal, is reversibly held in the protein pocket of the opsin protein by a C=N (Schiff Base) so it can be recycled after absorbing a photon. 11-Cis-retinal is a terpene, meaning it comes from plants (!) explaining why vitamin A (the alcohol form of retinal) is an ESSENTIAL vitamin in our diet (carrots, etc.).
2. Geminal diols form from water and a ketone or aldehyde according to the same mechanism as hemiacetal formation, namely Mechanism D. Hemiacetals are not stable relative to carbonyl aldehyde forms except for formaldehyde. Flashback: geminal diols are important in the chromic acid mechanism from last semester! Important result: Aldehydes are oxidized to carboxylic acids using H2CrO4 in H2O.
3. The Clemmensen reduction uses Zn(Hg) and HCl to convert the carbonyl groups of ketones and aldehydes into CH2 groups. The mechanism of this reaction is complex and will not be covered in this class. This reaction cannot be used if there are acid sensitive groups such as tertiary alcohols (they can lose H2O to give an alkene) or acetals present.
4. The Wolff-Kishner reduction, the one with the "scary" mechanism, uses NH2-NH2 and HO- to convert the carbonyl groups of ketones and aldehydes into CH2 groups. This reaction can be used when acid sensitive groups are present. The mechanism involves hydrazone formation, two detprotonations by HO-, loss of N2 and two protonations of the carbon atom that used to be the carbonyl carbon atom. Remember, the "Wolff " bites little red riding hood's head (aka carbonyl O atom) clean off!!
5. Oxidation-reduction reactions of carbonyl reactions are useful for putting together multiple reactions in sequence during organic synthesis.
Homework:
Read: Sections 17.1-17.4 in the ebook textbook. This text is part of the Longhorn Textbook access program.
Take the Daily Quiz 7 before 10 PM tomorrow. Click here to access the quiz. These quizzes are designed to review the important material from today's lecture.
Start working on the Homework Problem Set 4, due at 10 PM on Monday, February 12. Click here to access the Homework Problem Set 4. Remember to do both the Aktiv learning and Gradescope portions of the homework!