81. a. Propose a mechanism for the following reaction: OH CH2=CHCHC=N b. What is the product of the following reaction? HO H₂O N=CCH2CH2CH OH HO CH3CCH=CH2 H₂O C=N 82. Unlike a phosphonium ylide that reacts with an aldehyde or a ketone to form an alkene a sulfonium ulia

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4. Propose a mechanism for the following reaction: Conc. H₂SO4 HO

What is the major product(s) 2 formed after the following sequence of reactions? A A В в C D D E E OH 1. NaH 2. Br HI excess 1 Heat H. A and ОН and

What is the major product of the following reaction NaCN DMSO :and mechanism CN CN B C D C, SN2 .a A, E1 .b B, E2.C D, SN2 .d O

What is the product of the reaction below? OH LOH он Но. ???? но HCI OH он HO Но. Но- но но C D A В

PROVIDE REAGENTS NEEDED FOR THE FOLLOWING TRANSFORMATIONS: OH HO Br ad HMM H₂O S O TUOLI LOH LOH HT-HE Нови HOM.OH nodt 0.13 muidtillvaiV.A A 09,H.2 H.S STUGOR JA Ph HO₂C

5. Subjection of 1-bromo-1-methylcyclopentane to the hydrolytic conditions shown leads to a mixture of products. Br -CH3 H₂O heat -CH3 OH -CH3 =CH₂ + H3O+ + Br A B с a. Which alkene do you expect to be most abundant in the product mixture? b. Provide a stepwise mechanism to explain how the alkene labeled C is formed. c. The reaction above is shown with hydronium ion (pK₂~-1.7) and bromide as products rather than HBr (pKa ~ -9). Use acid-base concepts to explain why HBr does not exist when there is an abundance of water.

2. Propose a mechanism for the following reaction: OH Cl₂ CI.

Propose a reaction mechanism and fill in the product of the following transformation: & 1. NaH CO₂tBu ? 2. F NO2