Rules of the Day 320N

Featured Golden Rule of Chemistry. 5. Delocalization of charge over a larger area is stabilizing.7. Delocalization of pi electron density over a larger area is stabilizing. 9. Functional groups react the same in different molecules

1. The enol form of a carbonyl reacts like an alkene, so even though it is only present in small amounts, some reactions characteristic of alkenes can be made to occur with aldehydes and ketones such as halogenation with X2 at the alpha position.

2. Because acid catalysis increases the rate at which keto and enol forms equilibrate, reactions that proceed through the enol form such as halogenation on the alpha carbon atom are accelerated in acid.

3. Carboxylic acids are relatively acidic because the carboxylate anion is resonance stabilized, thereby distributing the negative charge over both oxygen atoms.

4. Carboxylic acids exist in solution as hydrogen bonded dimers. A good way to think about hydrogen bonds is as attraction between regions of molecules with partial positive charge (the H atom of an OH or NH bond) and the partial negative charge of a lone pair of electrons, usually on an O or N atom.

5.The stronger the acid, the lower the pKa and the more stable the conjugate base. Distribution of the negative charge over more atoms leads to a more stable conjugate base (Nature hates localized charges).

6. If the pH of a solution is higher than the pKa of an acid, the acid exists predominantly in its deprotonated state. If the pH of a solution is lower than the pKa of an acid, the acid exits predominantly in its protonated state. At neutral pH, as in biological systems, carboxylic acids are deprotonated and negatively charged, which is a BIG DEAL in biochemistry.

7. You can make carboxylic acids from Grignard reagents reacting with CO2 or oxidation of alcohols/aldehydes with H2CrO4.

8. You can reduce carboxylic acids to acohols with LiAlH4 followed by treatment with H2O. Other reducing agents do not work with carboxyilc acids.

9. Fischer esterification converts a carboxylic acid into an ester using an alcohol and acid catalysis. The mechanism involves Mechanism D followed by loss of an H2O via protonation.

Homework:

Read: Sections 17.5-17.9 in the ebook textbook. This text is part of the Longhorn Textbook access program.

Take the Daily Quiz 8 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 4, due at 10 PM on Wednesday, February 12. Click here to access the Homework Problem Set 4.

There is also an Aktiv Learning Homework Problem Set 4 as well (there was no Aktiv Learning homework Problem Set 1) click here to get the Aktiv Homework Problem set 4 (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).