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CHM 219 MODULE 4 TEST 2025| NEW ACTUAL
EXAM WITH ANSWERS
Two Main Types of Nucleophilic Substitution Reactions - Correct-answer-Sn1 and
Sn2
Sn2 - Correct-answer--single step (concerted)
-nucleophile attacks from the backside of the C-L bond. Nucleophile uses a lone
pair of electrons to begin making a bond to the carbon. Simultaneously the bond
between the C and the L begins to break. "Backside attack"
-Transition state: nucleophile and leaving group are both partly attached to
substrate.
-L departs from the substrate with the pair of electrons from the C-L bond and
nucleophile is fully bonded to the C
-Inversion of the tetrahedral geometry occurs.
*increasing the concentration of either the nucleophile or substrate will increase
the rate of the reaction
*2 is used becuae nucleophile and substrate are involved in the only step (key
step)
*methyl and primary alkyl halide react this way more easily
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FActors that influence the mechanistic path... of Sn2 - Correct-answer--Strength of
the nucleophile - SN2 depends on a strong Nucleophile, the more negative, the
stronger.
-Size of nucleophile - larger are more efficient
-Electronegativity of the Nucleophilic atom - the more electronegative, the less
nucleophilic
-Solvent chosen - they are polar and require polar solvents ; best solvents are
polar aprotic solvents
Sn1 - Correct-answer--two steps
-Step 1 - Leaving group leaves first. C-L bond breaks and produces 2 ionic
products: carbocation intermediate and a leaving group anion (this step is energy
intensive and very slow) known as the rate determining step (RDS)
-Step 2 - nucleophile attacks the carbocation intermediate, using a lone pair to
form a covalent bond.
*no inversion of tetrahedral geometry
*produces 50:50 enantiomers.
*secondary and tertiary typically react this way
Factors that influence the mechanistic path of... Sn1 - Correct-answer--nucleophile
size, strength , concentration and electronegativity have no effect
-solvent chosen - polar protic solvents - they can donate H bonds becuase they
have -OH, -NH, or -SH froup as part of their structure.
CHM 219 MODULE 4 TEST 2025| NEW ACTUAL
EXAM WITH ANSWERS
Two Main Types of Nucleophilic Substitution Reactions - Correct-answer-Sn1 and
Sn2
Sn2 - Correct-answer--single step (concerted)
-nucleophile attacks from the backside of the C-L bond. Nucleophile uses a lone
pair of electrons to begin making a bond to the carbon. Simultaneously the bond
between the C and the L begins to break. "Backside attack"
-Transition state: nucleophile and leaving group are both partly attached to
substrate.
-L departs from the substrate with the pair of electrons from the C-L bond and
nucleophile is fully bonded to the C
-Inversion of the tetrahedral geometry occurs.
*increasing the concentration of either the nucleophile or substrate will increase
the rate of the reaction
*2 is used becuae nucleophile and substrate are involved in the only step (key
step)
*methyl and primary alkyl halide react this way more easily
, 2|Page
FActors that influence the mechanistic path... of Sn2 - Correct-answer--Strength of
the nucleophile - SN2 depends on a strong Nucleophile, the more negative, the
stronger.
-Size of nucleophile - larger are more efficient
-Electronegativity of the Nucleophilic atom - the more electronegative, the less
nucleophilic
-Solvent chosen - they are polar and require polar solvents ; best solvents are
polar aprotic solvents
Sn1 - Correct-answer--two steps
-Step 1 - Leaving group leaves first. C-L bond breaks and produces 2 ionic
products: carbocation intermediate and a leaving group anion (this step is energy
intensive and very slow) known as the rate determining step (RDS)
-Step 2 - nucleophile attacks the carbocation intermediate, using a lone pair to
form a covalent bond.
*no inversion of tetrahedral geometry
*produces 50:50 enantiomers.
*secondary and tertiary typically react this way
Factors that influence the mechanistic path of... Sn1 - Correct-answer--nucleophile
size, strength , concentration and electronegativity have no effect
-solvent chosen - polar protic solvents - they can donate H bonds becuase they
have -OH, -NH, or -SH froup as part of their structure.
