Rules of the Day CH320M/328M

Featured Golden Rules of Chemistry: Nothing today

1. When studying for the exam, remember this material is very different then the first midterm material. You CAN do this. I suggest you follow these steps before looking through old exams: 1) Read each Rule of the Day so you can identify those things you are not familiar with. 2) Binge-watch the lectures recordings, skipping the things you undersrtand and spending time watching the things you do not yet understand (last year's class used this study method and they did great!) 3) Consult the Missed the Wave topics to see if you can get help from those recordings 4) Ask questions at office hours and the Review Session on Tuesday night 5) Start working through the old exams.

Study Tip for Today: Make sure you not only "know" the mechanisms, make sure you understand the role the different reagents play during each step (nucleophile, electrophile, strong acid, etc.)

2.Alkenes react with H2 in the presence of metals such as Pd, Pt, Ni to give alkanes. Reaction occurs on metal surface, and both H atoms add to same face of double bond leading to syn stereochemistry. Regiochemistry does not apply.

3. Alkenes react with 1. Hg(OAc)2 followed by 2) NaBH4 to give alchohols with Markovnikov regiochemistry and mixed stereochemistry. This cannot rearrange because there is no carbocation intermediate. You are not responsible for this reaction, but we wanted you to see it.

4. Alkynes with a hydrogen atom attached to one of the sp hybridized atoms are relatively acidic. This is because the anion produced upon deprotonation is on the sp atom, and more s character is stabilizing. Use the wicked strong base NaNH2 to deprotonate a terminal alkyne.

5. Deprotonated alkyne anions react as nucleophiles with primary haloalkanes in a single step in which the carbon-halogen bond is replaced with a carbon-carbon bond (Make a Bond between a nucleophile/electrophile and simultaneously Break a Bond to create stable molecules or ions). Big, mega deal here; We just made our first C-C bond!!! Time capsule: this is an SN2 reaction.

6. The chemistry of alkynes is predictable based on where the electrons are located: In two orthogonal pi bonds. Like alkenes, alkynes have the chemical personality of being a weak nucleophile, weak base.

7. Alkynes react with 2 equivalents of X2 and HX to give vicinal tetrahaloalkanes and dihaloalkanes, respectively. The HX reaction follows Markovnikov regiochemistry with terminal alkynes.

8. Alkynes are prepared from the base (NaNH2) promoted double elimination of a vicinal dihalide. For making an internal alkynes you need two equivalents of NaNH2, but for making terminal alkynes you need to 1. Add 3 equivalents of NaNH2 followed by 2. HCl/H2O to protonate the alkyne product. This provides a way to produce an alkyne from an alkene via the vicinal dihalide produced from an alkene and X2.

HOMEWORK:

Read: Study for the exam on Thursday.

There are no quizzes during exam week. These quizzes are designed to review the important material from today's lecture. Together, they will count as 5% of your final grade.

Keep working on the Exam 2 Practice Homework. It is not graded, you will not turn it in, and the answers have already been posted.