CHM 202 Practice Problems from Dr. Price's Archives CH 17-18

CHM 202 practice problems from Dr. Price’s archives CH 17-18 (& 19 nomenclature)

1.(12) Name the following compounds:

O Br Br a) H b) OH Cl O 5,5-dibromo-4-cyclobutyloctanal 2-chloro-4,4-dimethylcyclopentanone or δ,δ-dibromo-γ-cyclobutylcaprylaldehyde c) O OCH=CH2 d) H H e) (ethenyl) cyclohexyl vinyl ether (ethenyl) (Z) 3-heptene oxide 7-phenyl-1-octen-3-ol vinyloxycyclohexane cis (Z) 2-ethyl-3-propyloxirane (Z) 3,4-epoxyheptane

2.(8) Draw the following compounds. Be sure to show stereochemistry where appropriate:

a) (E) 2,3-dimethyl-3,4-epoxyhexane O

b) 4,5-dichloro-2-isopropyl-3-cyclopentenone O Cl

3.(10) A chemist attempted to synthesize t-butyl propyl ether by treating t-butyl chloride with potassium propoxide as shown below. A reaction occurred but gave none of the desired product. Instead she isolated a compound with a formula of C4H8 and an alcohol. Explain what happened (show what C4H8 is and how it forms – show the mechanism). How should she design her reaction in order to isolate the ether? CH H 3 CH3 CH3CH2CH2O K desired CH2 C Cl CH3CH2CH2OCCH3

CH3 none formed CH3

actual CH2=C(CH3)2 + CH3CH2CH2OH E2

C4H8 + an alcohol draw the reaction she should have run here

She should use a primary alkyl halide and a tertiary alkoxide to get the Williamson ether synthesis to work (SN2).

1) K metal (CH3)3COH (CH3)3COCH2CH2CH3 2) CH3CH2CH2Br

4.(40) Give the major product for each of the following reactions.

2 mol equiv. MCPBA a) OO in CH2Cl2

SOCl in pyridine b) OH 2 Cl

OH O c) CrO3, H2SO4 CH CHCH CH2CCH3 2 3 in acetone OH CH2Br 1) Mg, ether d) CH2CHCH2CH3 2) CH3CH2CH + O 3) H3O workup CH3 CH3

e) OH 1) NaH OCH2CH3 2) CH3CH2I

OH CH3 SO2Cl OH 1) f) pyridine

2) NaOH, DMSO (SN2) H g) 1) Hg(OAc)2, methanol

2) NaBH4 OCH3 CH CH CH CH h) 3 2 3 2 OCH2CH3 H 1) KOCH2CH3 in ethanol CC + CC 2) H3O CH CH3 3 H O H OH H O 1) LiAlH4 i) + H 2) H3O HO O PCC in CH Cl j) CH2OH 2 2 CH (pyridinium chlorochromate)

5.(10) Starting with alcohols of 5 carbons or less as your only source of carbon and any other reagents, show how the following alcohol could be prepared.

CH2CH3 OH OH COH

CH3 1) PBr3 Na2Cr2O7, + H3O 2) Mg, ether H2SO4 or PCC CH2CH3 MgBr O COMgBr + CH3

6.(14) Provide the reagents necessary (in the proper order) to carry out the following reactions: 1) ClSi(CH3)3, pyr. 2) NaBH4, THF + O 3) H3O (cold) CH a) CH2OH 4) SOCl2, pyridine O + Cl 5) H3O (deprotect) 6)

CrO3Cl N (PCC) H

1) NaBH4, THF O 2) H O+ 3 O b) 3) p-TsCl, pyridine CH3 4) KOC(CH3)3 / heat E2 CH3 CH3 5) CH3 If you use H2SO4 / ∆ CO3H in step 3 (E1), CH3 will migrate in carbocation. Cl

7.(10) Propose clear mechanism to account for the following transformations. Use only the reagents provided, show all intermediates and indicate electron flow with arrows.

b * Br a b * Na+H- + NaBr O *denotes a C-13 label O a

H Br a b *

O Na

8.(8) A student attempted to carry out a Grignard reaction of the ketone shown below in the attempt of isolating the 3o alcohol shown. Instead, she synthesized a 2o alcohol and the ketone was still intact. Explain. Propose structure for the product of the reaction.

CH3CH2 MgBr O OH 1) CH3CH2MgBr O O desired product (not formed

+ 2) H3O O O

O actual product H+ MgBr

9.(14) Propose a sequence of chemical steps in the proper order that facilitates the following transformations.

OH H

1) H2SO4 (aq) heat a) OCH(CH3)2 2) Hg(OAc)2, (CH3)2CHOH

3) NaBH4

O 1) CH3CH2MgBr b) + 2) H3O

3) H2SO4 (aq) heat OH gives 4) Hg(OAc)2, H2O-THF mixture 5) NaBH4 + 3) ClSi(CH ) , pyr. 4) CH CH MgBr or 1) Br2, hν 2) H3O (SN1) 3 3 3 2 O O O + 5) H3O

Br OH OSi(CH3)3