1. determine the type of pericyclic reaction (sigmatropic, electrocyclic, cycloaddition) 2. draw the mechanism for the reaction using curved arrows, and then use molecular orbital theory to evaluate the appropriate HOMO-LUMO interactions 3. determine the stereochemistry of the product, if necessary CHOOSE TWO OUT OF THE THREE PROBLEMS TO COMPLETE heat A RO, LOR 1. KH, THF RO, B RO .OR' 2. МеОН, Н20 OR' heat

Draw the structure of (Z)-1-bromo-1-chloro-1-butene. • Consider E/Z stereochemistry of alkenes. • You do not have to explicitly draw H atoms. AAVII ? ChemDoodle [F Ⓡ

44a) Draw the bond-line structure of 1,4-dimethyl-cyclohexa-1,3-diene here: STRUCTURE: b) Circle all the sp²-hybridized carbons in your drawing of the structure. c) In the spaces below, draw two potential products from a chlorination reaction (addition of Cl2) with your first structure Product 1: Product 2:

[References) Draw the line-angle formula for the most stable carbocation with a molecular formula of: C3H,+ • You do not have to consider stereochemistry. You do not have to explicitly draw H atoms. • If there are alternative structures, draw the most stable one. P opy aste ChemDoodle

Markovnikov Hydrohalogenation – HX (SYN & ANTI) :CI: H-CI: Scenario A :Cl: H. A В H-ci: H-CI: ..O :Cl: Scenario B CI: D 1. Fill in the curved arrows to show the mechanism of the reaction in Scenario A & B. 2. What is the hybridization and shape of the intermediate carbocation? How will the hybridization and shape of the intermediate carbocation affect the structure of the final product?

2. Our knowledge of chair conformations allows us to use them to determine a great deal about a reaction's mechanism. In particular, using a t-butyl group to 'fix' a cyclohexane in a single conformation can help us learn about the spatial requirements and energetics of a reaction. Consider the following two reaction products: a. NO NID ALOH 1) NaCN 2) H+ 1) NaBH4 2) H3O+ OH Group -H -CN -OH A Value (kcal/mol) Defined as 0 0.2 kcal/mol 1.0 kcal/mol Draw the most stable chair conformation for each of the two products. b. Based on the A values in the table above, do the two products have the most stable conformation at the new stereocenter?

What is the expected major product for the following reaction? O IV I OCH 3 |||||... + enantiomer || 1. Hg(OAc)2, CH3OH 2. NaBH4 НО. OH ... H3CO. + enantiomer ||| IV H3CO V

5. Consider the reaction below: ÇI CH3 CH CHCH3 CH, CHCHCH, + ci CH3 (a) State the type of bond cleavage involved. (b) Compare the stability of the product to (CH3)2CHCH;CH2 and explain.

4. Draw the mechanism that accounts for the formation of the product under the conditions shown. You may not add any other reagents. Be sure to show: all intermediate structures that occur in the course of the mechanism, any important resonance structures that play a role in the process, what if anything is added or lost in each step, and all formal charges on the structures. CHO H+ HO-C-H HO OH H-C-OH CH,OH НО 1 2 = 3

How many atoms of each hybridization state are there (sp,sp2, sp3)?What would be the result after the shown molecule is carried through the 4 step sequence? Show each intermediate and stereochemistry 1. 1eq. MeLi, then H2O workup 2.TsCl/pyr 3.NaOtBu/BuOH 4.OsO4/NaHSO3 And What is the relationship between the isomeric end products from them?