Updated November 7th, 2021 You know the drill, this is your go-to source for information concerning Organic Chemistry class! Past week's announcements will be saved in their respective quarter tabs.
Chapter 4 - Isomerism I - Conformational and Constitutional Isomers
This coming week, we are going to start Chapter 4 - Isomerism I - Conformational and Constitutional Isomers.
You are going to learn this week that a single chemical formula can give rise to many different compounds - we call these different compounds isomers of one another.
Whenever we characterize isomers, we are comparing the relationship between two molecules with the same chemical formula. The flow chart at right provides a means for categorizing isomers.
For Chapter 4, we will concern ourselves with only two classes of isomers:
conformational isomers - which differ only with respect to rotations about single bonds
constitutional isomers - which differ in connectivity, and can be easily separated from one another.
One can not study conformational isomers without an understanding of how the isomers appear in a Newman projection. Newman projections are a two-dimensional representation of a molecule viewed down the bond of interest.
Consider these rules when analyzing Newman projections:
The two atoms directly connected by the bond of interest are shown explicitly.
The nearer atom is depicted as a point.
The more distant atom is depicted as a circle.
Bonds to the front atom converge at the point, whereas bonds to the back atom connect to the circle.
The figure below from your textbook shows the Newman projections for a series of rotations about the C-C bond of a generic molecule, XCH2-CH2Y. In the figure, note the different views of the molecule and the dihedral angle, which corresponds to the angle between C-X and C-Y bonds.
Ideally, you should be able to look at a Newman projection, and draw a Lewis structure from it. From the figure below, can you draw the Lewis structure that corresponds to each?
Due to the challenges you will have on your ability to mentally rotate molecules, we will work with the modeling kits quite a bit over the next two chapters.
Week 12 Resources/ Assets
As already mentioned I will not be in class this coming Thursday.
Mrs. Sills will show you a video lecture I put together covering Sections 4.4 and 4.5.