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

2. Reacting an aromatic amine (like aniline) with NaNO2/HCl converts the NH2 group into a diazonium group (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).

3. 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.

4. 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.

5. 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.

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

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

8. Carbohydrates exist in the cyclic, hemiacetal form in solution. Click here for a second molecule of the day that discusses much of this. These are generally shown as Haworth projections. The mechanism involves the same steps at the hemiacetal formation mechanism you learned in Chapter 16.

9. A new chiral center is created (at the anomeric carbon) as the carbohydrate cyclizes, and the OH group can be axial (alpha equals axial for glucose) or equatorial (beta equals equatorial for glucose). For monosaccharides, these two forms are in equilibrium, and interconversion is catalyzed by acid (mutarotation).

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)

There is no daily quiz because of the midterm this week..

Contintue working on Homework 10 that will be due Wednesday, April 15th at 10 PM. Note, there are no Aktiv learning problem sets for the rest of the semester.

Click here for the Gradescope Homework Problem Set 10