CHM 2210 Exam 3 V2 | CHM 2210 Organic Chemistry I | Actual Q&A
with Rationale (CHM2210 Exam 3) | University of Central Florida
1. Which of the following describes the regioselectivity of the addition of HBr to 2-methyl-2-
butene?
A. Anti-Markovnikov addition
B. Syn-addition
C. Markovnikov addition
D. Free radical addition
Correct Answer: C
Explanation: The reaction follows Markovnikov’s rule because the proton adds to the
carbon with the most hydrogens. This pathway proceeds through the most stable
carbocation intermediate, which is tertiary in this specific molecule. Consequently, the
bromide ion attacks the carbocation to form the major product, 2-bromo-2-methylbutane.
2. What is the expected product when 1-heptyne is treated with H2SO4, HgSO4, and water?
A. Heptanal
B. 1-heptanol
C. 2-heptanone
D. Heptanoic acid
Correct Answer: C
Explanation: The acid-catalyzed hydration of a terminal alkyne using mercury(II) sulfate
results in a Markovnikov addition of water. The initially formed enol is unstable and
undergoes rapid tautomerization to form a methyl ketone. Therefore, 1-heptyne is
converted into 2-heptanone rather than an aldehyde.
3. Which reagent is used to convert an alkyne to a cis-alkene?
A. H2 / Lindlar’s catalyst
B. Na / NH3 (liq)
C. H2 / Pt
D. LiAl4
Correct Answer: A
,Explanation: Lindlar’s catalyst is a poisoned palladium catalyst that facilitates the partial
hydrogenation of alkynes to alkenes. The mechanism involves syn-addition of hydrogen
atoms to the same face of the triple bond, resulting in the cis-isomer. Treatment with
sodium in liquid ammonia would otherwise produce the trans-alkene via a radical-anion
mechanism.
4. What is the major product of the reaction between 1-methylcyclohexene and MCPBA?
A. 1-methylcyclohexanol
B. 1-methyl-1,2-cyclohexanediol
C. 1-methyl-1,2-epoxycyclohexane
D. 2-methylcyclohexanone
Correct Answer: C
Explanation: MCPBA is a peroxyacid reagent commonly used for the epoxidation of
alkenes. The reaction involves a concerted mechanism where an oxygen atom is
transferred to the pi bond to form a three-membered ring. This process is stereospecific
and preserves the original geometry of the substituted alkene.
5. Which of the following alkenes is the most stable?
A. 2,3-dimethyl-2-butene
B. cis-2-butene
C. trans-2-butene
D. 1-butene
Correct Answer: A
Explanation: Alkene stability increases with the degree of substitution due to
hyperconjugation and electronic effects. 2,3-dimethyl-2-butene is a tetrasubstituted alkene,
making it more stable than mono-, di-, or tri-substituted versions. Trans isomers are
generally more stable than cis isomers due to reduced steric strain between substituents.
6. The reaction of an alkene with Br2 in the presence of H2O yields which functional group?
A. Halohydrin
B. Geminal dibromide
C. Vicinal dibromide
D. Epoxide
Correct Answer: A
Explanation: When Br2 reacts with an alkene in an aqueous solvent, the water acts as a
nucleophile to open the bromonium ion intermediate. Water attacks the more substituted
, carbon of the bromonium ion, leading to a product with a bromine and a hydroxyl group.
This specific structural arrangement is known as a halohydrin.
7. Ozonolysis of 2-methyl-2-pentene followed by a reductive workup (DMS) yields which
products?
A. Acetone and Propanal
B. Propanal and Acetic acid
C. Acetone and Propanoic acid
D. 2-pentanone and Formaldehyde
Correct Answer: A
Explanation: Ozonolysis cleaves the carbon-carbon double bond, replacing it with two
carbonyl groups. Reductive workup with dimethyl sulfide (DMS) preserves aldehydes,
preventing them from oxidizing further to carboxylic acids. Cleaving 2-methyl-2-pentene
results in the formation of propanal and acetone (propanone).
8. How many degrees of unsaturation are present in a molecule with the formula C6H10?
A. 1
B. 2
C. 3
D. 0
Correct Answer: B
Explanation: The formula for degrees of unsaturation is (2C + 2 - H)/2. For C6H10, the
calculation is (2*6 + 2 - 10)/2, which equals (14 - 10)/2 = 2. This indicates the molecule
could contain two pi bonds, two rings, or one of each.
9. Which reagent is most suitable for the anti-Markovnikov hydration of an alkene?
A. H3O+
B. Hg(OAc)2, H2O followed by NaBH4
C. BH3-THF followed by H2O2, NaOH
D. KMnO4, NaOH, cold
Correct Answer: C
Explanation: Hydroboration-oxidation is a two-step sequence that results in the anti-
Markovnikov addition of water across an alkene. The boron atom adds to the less hindered
carbon, which is then replaced by a hydroxyl group. This reaction is stereospecific,
resulting in the syn-addition of H and OH.
with Rationale (CHM2210 Exam 3) | University of Central Florida
1. Which of the following describes the regioselectivity of the addition of HBr to 2-methyl-2-
butene?
A. Anti-Markovnikov addition
B. Syn-addition
C. Markovnikov addition
D. Free radical addition
Correct Answer: C
Explanation: The reaction follows Markovnikov’s rule because the proton adds to the
carbon with the most hydrogens. This pathway proceeds through the most stable
carbocation intermediate, which is tertiary in this specific molecule. Consequently, the
bromide ion attacks the carbocation to form the major product, 2-bromo-2-methylbutane.
2. What is the expected product when 1-heptyne is treated with H2SO4, HgSO4, and water?
A. Heptanal
B. 1-heptanol
C. 2-heptanone
D. Heptanoic acid
Correct Answer: C
Explanation: The acid-catalyzed hydration of a terminal alkyne using mercury(II) sulfate
results in a Markovnikov addition of water. The initially formed enol is unstable and
undergoes rapid tautomerization to form a methyl ketone. Therefore, 1-heptyne is
converted into 2-heptanone rather than an aldehyde.
3. Which reagent is used to convert an alkyne to a cis-alkene?
A. H2 / Lindlar’s catalyst
B. Na / NH3 (liq)
C. H2 / Pt
D. LiAl4
Correct Answer: A
,Explanation: Lindlar’s catalyst is a poisoned palladium catalyst that facilitates the partial
hydrogenation of alkynes to alkenes. The mechanism involves syn-addition of hydrogen
atoms to the same face of the triple bond, resulting in the cis-isomer. Treatment with
sodium in liquid ammonia would otherwise produce the trans-alkene via a radical-anion
mechanism.
4. What is the major product of the reaction between 1-methylcyclohexene and MCPBA?
A. 1-methylcyclohexanol
B. 1-methyl-1,2-cyclohexanediol
C. 1-methyl-1,2-epoxycyclohexane
D. 2-methylcyclohexanone
Correct Answer: C
Explanation: MCPBA is a peroxyacid reagent commonly used for the epoxidation of
alkenes. The reaction involves a concerted mechanism where an oxygen atom is
transferred to the pi bond to form a three-membered ring. This process is stereospecific
and preserves the original geometry of the substituted alkene.
5. Which of the following alkenes is the most stable?
A. 2,3-dimethyl-2-butene
B. cis-2-butene
C. trans-2-butene
D. 1-butene
Correct Answer: A
Explanation: Alkene stability increases with the degree of substitution due to
hyperconjugation and electronic effects. 2,3-dimethyl-2-butene is a tetrasubstituted alkene,
making it more stable than mono-, di-, or tri-substituted versions. Trans isomers are
generally more stable than cis isomers due to reduced steric strain between substituents.
6. The reaction of an alkene with Br2 in the presence of H2O yields which functional group?
A. Halohydrin
B. Geminal dibromide
C. Vicinal dibromide
D. Epoxide
Correct Answer: A
Explanation: When Br2 reacts with an alkene in an aqueous solvent, the water acts as a
nucleophile to open the bromonium ion intermediate. Water attacks the more substituted
, carbon of the bromonium ion, leading to a product with a bromine and a hydroxyl group.
This specific structural arrangement is known as a halohydrin.
7. Ozonolysis of 2-methyl-2-pentene followed by a reductive workup (DMS) yields which
products?
A. Acetone and Propanal
B. Propanal and Acetic acid
C. Acetone and Propanoic acid
D. 2-pentanone and Formaldehyde
Correct Answer: A
Explanation: Ozonolysis cleaves the carbon-carbon double bond, replacing it with two
carbonyl groups. Reductive workup with dimethyl sulfide (DMS) preserves aldehydes,
preventing them from oxidizing further to carboxylic acids. Cleaving 2-methyl-2-pentene
results in the formation of propanal and acetone (propanone).
8. How many degrees of unsaturation are present in a molecule with the formula C6H10?
A. 1
B. 2
C. 3
D. 0
Correct Answer: B
Explanation: The formula for degrees of unsaturation is (2C + 2 - H)/2. For C6H10, the
calculation is (2*6 + 2 - 10)/2, which equals (14 - 10)/2 = 2. This indicates the molecule
could contain two pi bonds, two rings, or one of each.
9. Which reagent is most suitable for the anti-Markovnikov hydration of an alkene?
A. H3O+
B. Hg(OAc)2, H2O followed by NaBH4
C. BH3-THF followed by H2O2, NaOH
D. KMnO4, NaOH, cold
Correct Answer: C
Explanation: Hydroboration-oxidation is a two-step sequence that results in the anti-
Markovnikov addition of water across an alkene. The boron atom adds to the less hindered
carbon, which is then replaced by a hydroxyl group. This reaction is stereospecific,
resulting in the syn-addition of H and OH.
