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Chemistry233Chapter11ProblemSet–Pt.1(SubstitutionReactions)

1. ConsidertheSN2reactionshownbelowandanswerthefollowingquestions.

A. Writetheratelawforthereaction.

B. Identifythenucleophileandtheelectrophileinthereaction.

C. Statehoweachofthefollowingfactorswouldaffecttherateofthereaction.a. Increasingtheconcentrationof1-bromopropane.

b. DecreasingtheconcentrationofNaSCH3byone-half.

c. Changing1-bromopropaneto2-bromopropane.

d. Changing1-bromopropaneto1-iodopropane.

e. ChangingNaSCH3toCH3OH.

2. ConsidertheSN1reactionshownbelowandanswerthefollowingquestions.

A. Writetheratelawforthereaction.

B. Identifythenucleophile,theelectrophile,andthereactionsolvent.

C. Statehoweachofthefollowingfactorswouldaffecttherateofthereaction.a. Increasingtheconcentrationofthealkylhalide.

b. IncreasingtheconcentrationofHOCH3.

c. ReplacingHOCH3withNaOCH3.

d. Changingthealkylhalidefromabromidetoaniodide.

e. Changingthealkylhalideto1-bromopropane.

Br + NaSCH3

acetone SCH3

+ Na + Br

PhBr + HOCH3 Ph

OCH3 + HBr

Chem.233–Chapter11-Pt.1ProblemSet

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3. Foreachofthefollowingpairs,circletheonethatwillproceedfasterbyanSN2reactionmechanism.

4. Foreachofthefollowingpairs,circletheonethatwillproceedfasterbyanSN1reactionmechanism.

F Br

Br Br

Cl Cl

Br + NaSCH3 Br + HSCH3

Br + NaF Br + NaIpolar protic solvent polar protic solvent

Br + NaFpolar aprotic solvent

Br + NaIpolar aprotic solvent

Cl+ NaOH

polar aprotic solvent

Cl+ NaSCH3

polar aprotic solvent

Br + KI (high conc) Br + KI (low conc)

vs

vs

vs

vs

vs

vs

vs

vs

BrBr

Cl Cl+ OH + OH

(high conc)(low conc)

Cl I

I I+ +NH3 NH2

Br Br+ HOEt

(Solvent) + HOEt (1 equiv)THF (solvent)

vs

vs

vs

vs

vs

vs

Br Br

Chem.233–Chapter11-Pt.1ProblemSet

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5. Explainwhythetworeactionsbelowprovideconstitutionallydifferentproducts.

6. Assumingeachreactionbelowundergoesnucleophilicsubstation,predictthemechanism(SN1orSN2)anddrawthemajorproduct.Includestereochemistrywhereappropriate.

Br

Br

HOCH3H3CO

NaOCH3

OCH3

Br

NaOH

NaOHBr

INaCN

ClNH3

Br NaSCH3

DMF

Br HO

I

I

OCH3

HOCH3

DMSO

Acetone

DMSO

Chem.233–Chapter11-Pt.1ProblemSet

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7. ThecompoundbelowcanundergoanintramolecularnucleophilicsubstitutionviaanSN2mechanism.Drawtheproductandthemechanismbywhichitisformed.

8. Explainwhythereactionbelowdoesnotprovideanyproductsfromnucleophilicsubstation.

HSEt

OH

H2O

HO

OCH3

HOCH3

DMSO

Br

DMSO

I

IH

Br

Br H2O

Br

Br

NH

Cl DMF

Br+ ONa

(NaOt-Bu)

No Substitution Reaction

Chem.233–Chapter11-Pt.1ProblemSet

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9. Predicttheproduct(s),withcorrectstereochemistryforeachofthefollowingsubstitutionreactionsinvolvinganalcoholstartingmaterial.

10. Showthecompleteelectronpushingmechanismforthereactioninquestion9a.

11. Showthecompleteelectronpushingmechanismforthereactioninquestion9d.

OH 1. TsCl Pyr2. NaBr

OH HBr

OHHI

OH

1. TsCl Pyr2. NaBr

NaITHF

OH

(a)

(b)

(c)

(e)

(f)

OHHBr

(d)