CHM 2210 Exam 4 V1 | CHM 2210 Organic Chemistry I | Actual Q&A
with Rationale (CHM2210 Exam 4) | University of Central Florida
1. Which of the following absorption frequencies in an IR spectrum would best characterize a
ketone functional group?
A. 1715 cm-1
B. 3300 cm-1
C. 2250 cm-1
D. 1650 cm-1
Correct Answer: A
Explanation: The carbonyl group (C=O) typically appears as a strong, sharp peak between
1700 and 1750 cm-1. Specifically, an unstrained acyclic ketone usually centers around
1715 cm-1. This distinction is critical when differentiating between alkenes, which appear
at lower frequencies, and alcohols, which appear much higher in the spectrum.
2. What is the degree of unsaturation (DoU) for a molecule with the molecular formula
C6H8O?
A. 2
B. 4
C. 3
D. 1
Correct Answer: C
Explanation: The formula for Degree of Unsaturation is (2C + 2 + N - H - X) / 2. For C6H8O,
this calculates to (2*6 + 2 - 8) / 2 = 3. This indicates the presence of three rings or pi bonds
within the structure, which is vital for structural elucidation.
3. Which reagent is most appropriate for the conversion of a primary alcohol to a carboxylic
acid?
A. Na2Cr2O7, H2SO4, H2O
B. PCC, CH2Cl2
C. Dess-Martin Periodinane
D. LiAlH4, ether
Correct Answer: A
,Explanation: Jones reagent (sodium dichromate in sulfuric acid) is a strong oxidant that
converts primary alcohols directly to carboxylic acids. Mild oxidants like PCC or DMP
would stop the reaction at the aldehyde stage. Understanding the strength of various
oxidizing agents is essential for controlling product outcome in organic synthesis.
4. In 1H NMR spectroscopy, what is the expected chemical shift for protons attached to a
carbon directly bonded to an oxygen atom in an ether?
A. 0.9 - 1.5 ppm
B. 3.3 - 4.5 ppm
C. 2.1 - 2.5 ppm
D. 7.0 - 8.0 ppm
Correct Answer: B
Explanation: Electronegative atoms like oxygen deshield neighboring protons, causing
them to resonate at higher chemical shifts. Protons on carbons alpha to an oxygen typically
appear in the 3.3 to 4.5 ppm range. This shift is higher than alkyl protons but lower than
aromatic or aldehydic protons.
5. What is the major product formed when 1-methylcyclohexene reacts with mCPBA,
followed by H3O+?
A. cis-1-methylcyclohexane-1,2-diol
B. trans-1-methylcyclohexane-1,2-diol
C. 1-methylcyclohexanol
D. 2-methylcyclohexanol
Correct Answer: B
Explanation: Reaction with mCPBA forms an epoxide across the double bond. Subsequent
acid-catalyzed ring opening occurs via an anti-addition mechanism due to the nucleophilic
attack on the epoxide. This results in the trans-diol, reflecting the stereospecific nature of
the epoxide opening process.
6. Which of the following compounds would show a signal at approximately 200 ppm in 13C
NMR spectroscopy?
A. Benzene
B. Acetone
C. Cyclohexanol
D. Ethyl acetate
Correct Answer: B
, Explanation: Carbonyl carbons of aldehydes and ketones typically appear between 190
and 220 ppm. Esters and carboxylic acids appear slightly lower, usually between 160 and
185 ppm. Therefore, acetone (a ketone) is the only structure among the choices that fits
this highly deshielded range.
7. Which test can distinguish between a primary alcohol and a tertiary alcohol almost
immediately?
A. Lucas Test
B. Tollens Test
C. Iodoform Test
D. Bromine Test
Correct Answer: A
Explanation: The Lucas test uses ZnCl2 in concentrated HCl to differentiate alcohols based
on their rate of SN1 reaction. Tertiary alcohols react immediately to form a cloudy
emulsion of alkyl chloride, whereas primary alcohols may not react for hours. This test is a
classic qualitative method for determining the degree of substitution at the hydroxyl-
bearing carbon.
8. Identify the reagent required to convert an epoxide into a primary alcohol with two
additional carbons.
A. Ethylmagnesium bromide, then H3O+
B. CH3MgBr, then H3O+
C. NaBH4, then H2O
D. H2, Pd/C
Correct Answer: A
Explanation: Grignard reagents act as nucleophiles that attack the less substituted carbon
of an epoxide. Using ethylmagnesium bromide (two carbons) followed by protonation
results in the addition of an ethyl group to the epoxide skeleton. This is a common method
for chain elongation in organic synthesis.
9. What is the characteristic mass spectrometry fragment for an alkyl benzene, such as
ethylbenzene, at m/z 91?
A. Phenyl cation
B. Tropylium cation
C. Methyl cation
D. Benzylic radical
with Rationale (CHM2210 Exam 4) | University of Central Florida
1. Which of the following absorption frequencies in an IR spectrum would best characterize a
ketone functional group?
A. 1715 cm-1
B. 3300 cm-1
C. 2250 cm-1
D. 1650 cm-1
Correct Answer: A
Explanation: The carbonyl group (C=O) typically appears as a strong, sharp peak between
1700 and 1750 cm-1. Specifically, an unstrained acyclic ketone usually centers around
1715 cm-1. This distinction is critical when differentiating between alkenes, which appear
at lower frequencies, and alcohols, which appear much higher in the spectrum.
2. What is the degree of unsaturation (DoU) for a molecule with the molecular formula
C6H8O?
A. 2
B. 4
C. 3
D. 1
Correct Answer: C
Explanation: The formula for Degree of Unsaturation is (2C + 2 + N - H - X) / 2. For C6H8O,
this calculates to (2*6 + 2 - 8) / 2 = 3. This indicates the presence of three rings or pi bonds
within the structure, which is vital for structural elucidation.
3. Which reagent is most appropriate for the conversion of a primary alcohol to a carboxylic
acid?
A. Na2Cr2O7, H2SO4, H2O
B. PCC, CH2Cl2
C. Dess-Martin Periodinane
D. LiAlH4, ether
Correct Answer: A
,Explanation: Jones reagent (sodium dichromate in sulfuric acid) is a strong oxidant that
converts primary alcohols directly to carboxylic acids. Mild oxidants like PCC or DMP
would stop the reaction at the aldehyde stage. Understanding the strength of various
oxidizing agents is essential for controlling product outcome in organic synthesis.
4. In 1H NMR spectroscopy, what is the expected chemical shift for protons attached to a
carbon directly bonded to an oxygen atom in an ether?
A. 0.9 - 1.5 ppm
B. 3.3 - 4.5 ppm
C. 2.1 - 2.5 ppm
D. 7.0 - 8.0 ppm
Correct Answer: B
Explanation: Electronegative atoms like oxygen deshield neighboring protons, causing
them to resonate at higher chemical shifts. Protons on carbons alpha to an oxygen typically
appear in the 3.3 to 4.5 ppm range. This shift is higher than alkyl protons but lower than
aromatic or aldehydic protons.
5. What is the major product formed when 1-methylcyclohexene reacts with mCPBA,
followed by H3O+?
A. cis-1-methylcyclohexane-1,2-diol
B. trans-1-methylcyclohexane-1,2-diol
C. 1-methylcyclohexanol
D. 2-methylcyclohexanol
Correct Answer: B
Explanation: Reaction with mCPBA forms an epoxide across the double bond. Subsequent
acid-catalyzed ring opening occurs via an anti-addition mechanism due to the nucleophilic
attack on the epoxide. This results in the trans-diol, reflecting the stereospecific nature of
the epoxide opening process.
6. Which of the following compounds would show a signal at approximately 200 ppm in 13C
NMR spectroscopy?
A. Benzene
B. Acetone
C. Cyclohexanol
D. Ethyl acetate
Correct Answer: B
, Explanation: Carbonyl carbons of aldehydes and ketones typically appear between 190
and 220 ppm. Esters and carboxylic acids appear slightly lower, usually between 160 and
185 ppm. Therefore, acetone (a ketone) is the only structure among the choices that fits
this highly deshielded range.
7. Which test can distinguish between a primary alcohol and a tertiary alcohol almost
immediately?
A. Lucas Test
B. Tollens Test
C. Iodoform Test
D. Bromine Test
Correct Answer: A
Explanation: The Lucas test uses ZnCl2 in concentrated HCl to differentiate alcohols based
on their rate of SN1 reaction. Tertiary alcohols react immediately to form a cloudy
emulsion of alkyl chloride, whereas primary alcohols may not react for hours. This test is a
classic qualitative method for determining the degree of substitution at the hydroxyl-
bearing carbon.
8. Identify the reagent required to convert an epoxide into a primary alcohol with two
additional carbons.
A. Ethylmagnesium bromide, then H3O+
B. CH3MgBr, then H3O+
C. NaBH4, then H2O
D. H2, Pd/C
Correct Answer: A
Explanation: Grignard reagents act as nucleophiles that attack the less substituted carbon
of an epoxide. Using ethylmagnesium bromide (two carbons) followed by protonation
results in the addition of an ethyl group to the epoxide skeleton. This is a common method
for chain elongation in organic synthesis.
9. What is the characteristic mass spectrometry fragment for an alkyl benzene, such as
ethylbenzene, at m/z 91?
A. Phenyl cation
B. Tropylium cation
C. Methyl cation
D. Benzylic radical
