Rules of the Day 4-30-07

An optional review session for the final will be given: Wednesday, May 2 Room: WEL 2.224

For the review session, please bring any extra canned food items you have in your dorm rooms so that I can donate them to the Caritas House

Click here for today's first lecture sheet

Click here for today's second lecture sheet

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

2. 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.

3. 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).

4. Cyclic form carbohydrates form either five (furanose) or six (pyranose) membered rings.

5. Carbohydrate monomers can be linked together via acetal bonds, and this linkage can be alpha or beta. (For glucose, alpha is axial) This type of acetal bond is called a glycosidic bond and is named as alpha or beta referring to the stereochemistry of the anomeric carbon and also by the numbers of the ring carbons attached via the -C-O-C- linkage (i.e. alpha 1,4-). Click here for a third molecule of the day that discusses much of this.

6. Sucrose is glucose linked to fructose.

Homework: Continue the 10th and final homework set. This one is focussed on the material we have covered since the midterm. It is due on Friday May 5th, the last day of class.