Rules of the Day
1-30-2025
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. Cyclic hemiacetals that form five- or six-membered rings are stable (as opposed to non-cyclic hemiacetals which are not stable species). Carbohydrate monomers like D-Glucose are actually found in the cyclic hemiacetal state in solution (SWEET!). In carbohydrates, the new C-O bond is formed to the so-called anomeric carbon, and for D-glucose, alpha means the new OH group is axial, and beta means it is equatorial.
2. Water behaves the same as alcohols in most reaction mechanisms.
3. 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.
4. Protecting groups are chemical functions that can reversibly mask a reactive functional group to prevent an unwanted reaction. The protecting group is added prior to the reaction in question, then removed following the reaction in question.
5. 5- or 6-membered ring cyclic acetals are good protecting groups for use with Grignard reagents, since the cyclic acetals can be reversibly attached, and they have an sp3 carbon atom that won't react with nucleophiles like carbonyls do.
6. Imines are formed when a primary amine or ammonia reacts with an aldehyde or ketone with some acid around. The mechanism involves mechanism C to make an aminal, followed by protonation of the OH group then loss of water at the same time a proton is lost from the nitrogen atom. Like acetal formation, this process is reversible and can be run in either direction depending on the ratio of amine (ammonia) to water in the solution.
7. 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.)
Homework:
Read: Sections 16.9, 16.12 in the ebook textbook. This text is part of the Longhorn Textbook access program.
Take the Daily Quiz 6 before 10 PM tomorrow. Click here to access the quiz. These quizzes are designed to review the important material from today's lecture. Together, they will count as 3% of your final grade.
Start working on the Gradescope Homework Problem Set 3, due at 10 PM on Wednesday, February 5. Click here to access the Homework Problem Set 3.
There is also an Aktiv Learning Homework Problem Set 3 as well (there was no Aktiv Learning homework Problem Set 1) If you already have an Aktiv Learning account, click here to get the Aktiv Homework Problem set 3 (there was no Aktiv Homework Problem set 1)
Homeworks will be worth 10% of your final grade (20% from the Aktiv Learning and 80% from the Gradescope portions of the homework).
