Page 1 of 5 Chemistry 233 Chapter 11 Problem Set – Pt. 1 (Substitution Reactions) 1. Consider the SN2 reaction shown below and answer the following questions. A. Write the rate law for the reaction. B. Identify the nucleophile and the electrophile in the reaction. C. State how each of the following factors would affect the rate of the reaction. a. Increasing the concentration of 1-bromopropane. b. Decreasing the concentration of NaSCH3 by one-half. c. Changing 1-bromopropane to 2-bromopropane. d. Changing 1-bromopropane to 1-iodopropane. e. Changing NaSCH3 to CH3OH. 2. Consider the SN1 reaction shown below and answer the following questions. A. Write the rate law for the reaction. B. Identify the nucleophile, the electrophile, and the reaction solvent. C. State how each of the following factors would affect the rate of the reaction. a. Increasing the concentration of the alkyl halide. b. Increasing the concentration of HOCH3. c. Replacing HOCH3 with NaOCH3. d. Changing the alkyl halide from a bromide to an iodide. e. Changing the alkyl halide to 1-bromopropane. Br + NaSCH 3 acetone S CH 3 + Na + Br Ph Br + HOCH 3 Ph O CH 3 + HBr
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Page 1 of 5
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)
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