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 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.The enol form of a compound rapidly tautomerizes to the more stable keto form. The keto form is more stable because the C=O pi bond is stronger than the C=C pi bond.

3. Alkynes give enols that rapidly tautomerize to ketones or aldehydes when reacted with 1. BH3 2. H2O2/NaOH. To see a strong preference for the terminal side of an alkyne (non-Markovnikov), use the bulkier (sia)2BH.("borane with antlers")

4. Alkynes add water in the presence HgSO4/H2SO4 to give enols that tautomerize to ketones. For terminal alkynes, the oxygen atom ends up on the internal carbon atom as Markovnikov would predict. You are not responsible for the really long mechanism that involves a mercurinium ion intermediate and eventually loss of Hg2+ to give the enol that tautomerizes to the keto form.

5. Catalytic reduction using H2 takes an alkyne all the way to an alkane when elemental catalyst such as Pd is used. When a kinder/gentler catalyst called Lindlar's catalyst is used, the reaction stops at the alkene stage, stereochemistry of addition is syn, leading to cis products.

6. Flashback Rule of the Day: Trans alkenes are more stable thatn cis alkenes because cis alkenes have some steric strain (non-bonded intereatction strain). In addition, more highly substituted alkenes are more stable than less substituted alkenes (we don't really tell you why, just learn it please.)

7. Chemical reduction using sodium (Na) in liquid ammonia (NH3) gives a trans alkene. The mechanism involves single electron transfers and radical/anion intermediates, resulting from sequential electron and proton transfers, repeated a second time.

HOMEWORK:

Read: Study for the exam on Thursday.

There is no quiz today because it is 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.

Finish Working on Homework Problem Set 7, due at 10 PM today, October 22.

Click here to go to the Aktive Homework Problem Set 7

Click here to get a copy of the Gradescope Homework Problem Set 7