Rules of the Day 320N

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

1. Amines are good bases (pKa of conjugate acid is around 10) and strong nucleophiles in SN2 and Michael reactions. Amines are protonated and positively charged at neutral pH in water.

2. Our sense of smell is tuned to detect molecules that indicate spoiled food by detecting certain characteristic molecules resulting from microbial contamination and degradation. Simple diamines indicate rotten mammal flesh, triethyl amine indicates rotten fish, thiols such as hydrogen sulfide indicate rotten eggs among other spoiled food and butyric acid indicates vomit. Our noses are capable of detecting as little as a few parts per billion of some of these molecules.

3. Because of pi delocalization, an amino group attached to a benzene ring is close to or fully sp2 hybridized. This explains why the DNA bases are planar!!

4. Reaction of nitro(-NO2) groups on aromatic rings with H2 in the presence of Ni produces an amine (-NH2).

5. Reacting an aromatic amine (like aniline) with NaNO2/HCl converts the NH2 group into N2+, the famous "Mr. Bill" reaction (HONO!!!!). The N2+ can be replaced by OH (using H2O), F (using HBF4), CN (using KCN and CuCN), Cl (using HCl and CuCl), Br (using HBr and CuBr), I (using KI), H (using H3PO2). Recall that the starting aromatic amine can come from reduction of a nitro aromatic (H2/Ni), and the nitro aromatic can come from nitration of an aromatic ring (HNO3, H2SO4).

6. If an aromatic ring is loaded with electron withdrawing groups, it is no longer nucleophilic, but can react as an electrophile. In this case, strong nucleophiles can displace a halogen on an aromatic ring. We will only see one example of this very rare and special reaction, in which 2,4-dinitrofluorobenzene reacts with strong nucleophiles such as amines. This is called nucleophilic aromatic substitution, and is very, very rare compared to electrophilic aromatic substitution reactions.

7. Final Piece of Aromatic Chemisty. Rings with a Bad group are so deactivated that neither the Friedel-Crafts alkylation or acylation will work. However, you can add multiple NO2 groups to the same ring if you run the reaction long and hot enough.

8. THE KEY issue with carbohydrates is stereochemistry. The stereochemistry of carbohydrates are based on (+) D and (-) L glyceradehyde. A D-sugar has the same configuration as (+)-D-glyceraldehyde at the chiral center farthest from the carbonyl group. An L-sugar has the same configuration as (-) -L-glyceraldehyde at the chiral center farthest from the carbonyl group. The best way to see this is with Fisher projections. Click here for a molecule of the day that discusses much of this.

9. With Fisher projections, horizontal is toward you, vertical is away from you. Think of it like a teddy bear hugging you. Aaahhhh.

10. Different stereoisomers of similar carbohydrates can be aldehydes (aldose) or ketones (ketose) and they will have different names and generally have 5 (pentose) or 6 (hexose) carbon atoms.

Homework:

No more reading assignments this semester!!

Many students have difficulty understanding how to think about "equivalents", how to balance certain equations like the Claisen condensation, what do we mean by H3O+ and knowing when to use hydroxide versus ethoxide. Here are some short videos to help you with any of these: How to think about "Equivalents" when using base in enolate reactions (7:17 minutes) Correct video for How to think about "Equivalents" when using base in enolate reactions (3:29 minutes) How to balance a Claisen reaction equation (5:06 minutes) What do we mean by H3O+ (2:52 minutes) When to use NaOH vs. NaOEt (7:35 minutes) Homework:

There is no daily quiz because of the exam.

Finish working on the Homework 10 that will be due on April 16. Click here to get a copy. This is a good guide for what types of questions from the new material will be on the midterm this week.