Tuesday, November 20, 2007

Sample Exam 2 Posted

I posted a sample exam for exam #2 on the shared files page (233sample_ex2.pdf). You may work through this example to help you study. I do not recommend relying soley on this example; also look at homework questions and TA notes for additional material.

Monday, November 19, 2007

Stereoselectivity in E1

There have been several questions about the stereoselectivity of an E1 elimination mechanism. Two arguments can be made. A kinetic argument compares the relative energies of the carbocation intermediates leading to each product. The carbocation intermediate on the left is more stable than the carbocation intermediate on the right due to reduced steric strain; therefore the trans alkene is favored. Because this reaction is reversible a thermodynamic argument can also be made and is actually more correct; although the outcome is the same in this instance. Thus, the trans alkene product is favored because it is more stable (lower in energy) than the cis alkene. Trans is more stable than cis for the same reason already mentioned, less steric strain. Caution: thermodynamic arguments (comparing relative stabilities of products) can only be made when reactions are reversible (equilibrium). This reaction is reversible and explains why distillation was necessary to remove the alkene products and shift the equilibrium toward products (LeChatleir principle).

Thursday, November 15, 2007

Final Exam

CHEM 233 final exam will meet according to the schedule below. The exams will start on time so please arrive early so that you may find your seat. Again, a final exam information sheet will be distributed on the day of your practical. Happy Thanksgiving.

Monday-Thursday sections: Monday, Dec. 10, 6pm-7pm, Lecture Center B1.

Friday sections: Monday, Dec. 10, 6:15pm-7:15pm, Lecture Center A1.

Monday, November 12, 2007

Weeks 14-16 Schedule

Week 14 (November 26-30): Practical Exam

Week 15 (December 3-7): Exam 2 and Drawer Checkout.

Week 16 (December 10): Final Exam, 6pm, LC A1 & B1. Please see final exam info sheet to determine which room your exam is in.

233 Final Exam Time

The final exam for CHEM 233 will be held on Monday, December 10 from 6-8pm in Lecture Centers A1 and B1. Because there are two rooms, the class will be divided in half. You will receive an informational sheet on the day of your practical exam that will indicate which Lecture Center you should attend. This info sheet will also contain sample questions, review topics as well as exam policies.

An Organic Chem Blog????

Well, I've finally entered the world of blogging after having spent probably hundreds of hours reading the blogs of others. It feels good, although I'm a little skeptical since I tend to be a perfectionist and reread my writing over and over until I am satisfied. I'm somewhat comforted that this blog is dedicated to organic chemistry--a topic I could write endlessly about. Initially, I anticipate the blog to more or less function as an announcement board for CHEM 233 and CHEM 333, especially for the remaining Fall 2007 semester. However, I certainly hope it can grow into a platform for initiating interesting discussions in chemistry. It may even be entertaining, but that might be stretching. . .