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CHEM 228 ORGANIC CHEMISTRY II FULL PACKAGE
QUESTIONS ANSWERS AND RATIONALES 2026-27
LATEST UPDATED VERSION
INSTANT DOWNLOAD PDF..!!
INTRODUCTION
The CHEM 228 Organic Chemistry II course is a rigorous continuation of
foundational organic chemistry, building upon the principles of structure,
bonding, and reactivity to explore the chemistry of carbonyl compounds,
aromatic systems, and biomolecules . This course, offered as part of the Texas
A&M University chemistry curriculum, delves deeply into the mechanisms,
stereochemistry, and synthetic applications of key organic reactions . Students
are expected to master concepts such as nucleophilic acyl substitution, aldol
and Claisen condensations, conjugate additions, and the chemistry of amines
and carboxylic acid derivatives . The course emphasizes problem-solving skills,
requiring students to predict reaction outcomes, propose multi-step syntheses,
and analyze spectroscopic data . This question bank contains 200 advanced,
exam-style questions that mirror the content, difficulty, and format of the
actual CHEM 228 examinations, including the application of IR and NMR
spectroscopy to structure determination . Each question includes a detailed
rationale explaining the correct answer and why other options are incorrect.
With this resource, you will identify knowledge gaps, build confidence, and
develop the test-taking strategies needed to succeed in this challenging course.
CORE DOMAINS TESTED
1. Spectroscopy and Structure Determination – Infrared (IR) spectroscopy,
Nuclear Magnetic Resonance (NMR) spectroscopy (¹H and ¹³C), and mass
spectrometry for structural elucidation .
2. Carbonyl Chemistry: Addition and Substitution – Nucleophilic addition
to aldehydes and ketones, nucleophilic acyl substitution (acid chlorides,
esters, amides, and carboxylic acids), and relative reactivities of carbonyl
compounds .
,2
3. Enolate Chemistry and Condensation Reactions – Formation of
enolates, aldol addition and condensation, Claisen condensation,
Michael addition, and Robinson annulation .
4. Aromatic Chemistry – Electrophilic aromatic substitution (nitration,
halogenation, Friedel-Crafts alkylation and acylation, sulfonation),
directing effects, and synthesis of substituted benzenes.
5. Chemistry of Amines and Nitrogen Compounds – Basicity, synthesis, and
reactions of amines, including diazonium salts.
6. Biomolecules and Pericyclic Reactions – Carbohydrates, amino acids and
proteins, nucleic acids, lipids, and Diels-Alder reactions.
7. Synthesis and Retrosynthesis – Planning multi-step syntheses using
reactions from all domains .
,3
Q1: A compound with the molecular formula C₈H₆O₂ shows a strong
IR absorption at 1690 cm⁻¹ and ¹H NMR signals: δ 10.2 (s, 1H), δ 8.2-
7.5 (m, 5H). The ¹³C NMR shows a signal at δ 191.4 (d). What is the
most likely structure?
A) Acetophenone
B) Benzaldehyde
C) Benzoic acid
D) Methyl benzoate
Rationale: The correct answer is B. The IR absorption at 1690 cm⁻¹
indicates a conjugated carbonyl (aryl aldehyde or ketone). The ¹H
NMR signal at δ 10.2 is characteristic of an aldehyde proton (CHO).
The ¹³C NMR signal at δ 191.4 is consistent with an aldehyde
carbonyl. The molecular formula C₈H₆O₂ (eight carbons, six
hydrogens, two oxygens) and the aromatic proton multiplet (δ 8.2-
7.5, 5H) fits benzaldehyde (C₆H₅CHO). Option A is incorrect because
acetophenone (C₆H₅COCH₃) would have a methyl singlet around δ 2.5
and no aldehyde proton. Option C is incorrect because benzoic acid
(C₆H₅COOH) would show a broad OH signal around δ 10-12 and a
carbonyl absorption near 1680-1700 cm⁻¹, but the aldehyde proton
would be absent. Option D is incorrect because methyl benzoate
(C₆H₅COOCH₃) would show a methoxy singlet around δ 3.9 and no
aldehyde proton .
Q2: Rank the following carboxylic acid derivatives in order of
increasing reactivity toward nucleophilic acyl substitution: I) Acid
chloride, II) Anhydride, III) Ester, IV) Amide.
, 4
A) I < II < III < IV
B) IV < III < II < I
C) II < I < IV < III
D) IV < II < III < I
Rationale: The correct answer is B. Reactivity toward nucleophilic acyl
substitution is determined by the leaving group ability and the
electrophilicity of the carbonyl carbon. Acid chlorides are the most
reactive because chloride is a good leaving group and the carbonyl
carbon is highly electrophilic. Anhydrides are less reactive than acid
chlorides but more reactive than esters. Esters are less reactive than
anhydrides but more reactive than amides. Amides are the least
reactive because nitrogen is a poor leaving group and the lone pair
on nitrogen donates into the carbonyl, reducing electrophilicity. The
correct order of increasing reactivity is Amide < Ester < Anhydride <
Acid Chloride (IV < III < II < I). Option A is incorrect because it reverses
the order. Option C is incorrect because it places anhydride before
acid chloride. Option D is incorrect because it places amide as the
most reactive .
Q3: Which of the following statements best explains why acid
chlorides are more reactive toward nucleophilic acyl substitution
than esters?
A) Chlorine is more electronegative than oxygen
B) The chloride ion is a better leaving group than alkoxide
C) Esters have stronger carbon-oxygen bonds
D) Acid chlorides are more sterically hindered
Rationale: The correct answer is B. In nucleophilic acyl substitution,
the leaving group departs after the tetrahedral intermediate is
formed. The ability of the leaving group to depart is a key factor in
determining reactivity. Chloride ion (Cl⁻) is a weak base and an
CHEM 228 ORGANIC CHEMISTRY II FULL PACKAGE
QUESTIONS ANSWERS AND RATIONALES 2026-27
LATEST UPDATED VERSION
INSTANT DOWNLOAD PDF..!!
INTRODUCTION
The CHEM 228 Organic Chemistry II course is a rigorous continuation of
foundational organic chemistry, building upon the principles of structure,
bonding, and reactivity to explore the chemistry of carbonyl compounds,
aromatic systems, and biomolecules . This course, offered as part of the Texas
A&M University chemistry curriculum, delves deeply into the mechanisms,
stereochemistry, and synthetic applications of key organic reactions . Students
are expected to master concepts such as nucleophilic acyl substitution, aldol
and Claisen condensations, conjugate additions, and the chemistry of amines
and carboxylic acid derivatives . The course emphasizes problem-solving skills,
requiring students to predict reaction outcomes, propose multi-step syntheses,
and analyze spectroscopic data . This question bank contains 200 advanced,
exam-style questions that mirror the content, difficulty, and format of the
actual CHEM 228 examinations, including the application of IR and NMR
spectroscopy to structure determination . Each question includes a detailed
rationale explaining the correct answer and why other options are incorrect.
With this resource, you will identify knowledge gaps, build confidence, and
develop the test-taking strategies needed to succeed in this challenging course.
CORE DOMAINS TESTED
1. Spectroscopy and Structure Determination – Infrared (IR) spectroscopy,
Nuclear Magnetic Resonance (NMR) spectroscopy (¹H and ¹³C), and mass
spectrometry for structural elucidation .
2. Carbonyl Chemistry: Addition and Substitution – Nucleophilic addition
to aldehydes and ketones, nucleophilic acyl substitution (acid chlorides,
esters, amides, and carboxylic acids), and relative reactivities of carbonyl
compounds .
,2
3. Enolate Chemistry and Condensation Reactions – Formation of
enolates, aldol addition and condensation, Claisen condensation,
Michael addition, and Robinson annulation .
4. Aromatic Chemistry – Electrophilic aromatic substitution (nitration,
halogenation, Friedel-Crafts alkylation and acylation, sulfonation),
directing effects, and synthesis of substituted benzenes.
5. Chemistry of Amines and Nitrogen Compounds – Basicity, synthesis, and
reactions of amines, including diazonium salts.
6. Biomolecules and Pericyclic Reactions – Carbohydrates, amino acids and
proteins, nucleic acids, lipids, and Diels-Alder reactions.
7. Synthesis and Retrosynthesis – Planning multi-step syntheses using
reactions from all domains .
,3
Q1: A compound with the molecular formula C₈H₆O₂ shows a strong
IR absorption at 1690 cm⁻¹ and ¹H NMR signals: δ 10.2 (s, 1H), δ 8.2-
7.5 (m, 5H). The ¹³C NMR shows a signal at δ 191.4 (d). What is the
most likely structure?
A) Acetophenone
B) Benzaldehyde
C) Benzoic acid
D) Methyl benzoate
Rationale: The correct answer is B. The IR absorption at 1690 cm⁻¹
indicates a conjugated carbonyl (aryl aldehyde or ketone). The ¹H
NMR signal at δ 10.2 is characteristic of an aldehyde proton (CHO).
The ¹³C NMR signal at δ 191.4 is consistent with an aldehyde
carbonyl. The molecular formula C₈H₆O₂ (eight carbons, six
hydrogens, two oxygens) and the aromatic proton multiplet (δ 8.2-
7.5, 5H) fits benzaldehyde (C₆H₅CHO). Option A is incorrect because
acetophenone (C₆H₅COCH₃) would have a methyl singlet around δ 2.5
and no aldehyde proton. Option C is incorrect because benzoic acid
(C₆H₅COOH) would show a broad OH signal around δ 10-12 and a
carbonyl absorption near 1680-1700 cm⁻¹, but the aldehyde proton
would be absent. Option D is incorrect because methyl benzoate
(C₆H₅COOCH₃) would show a methoxy singlet around δ 3.9 and no
aldehyde proton .
Q2: Rank the following carboxylic acid derivatives in order of
increasing reactivity toward nucleophilic acyl substitution: I) Acid
chloride, II) Anhydride, III) Ester, IV) Amide.
, 4
A) I < II < III < IV
B) IV < III < II < I
C) II < I < IV < III
D) IV < II < III < I
Rationale: The correct answer is B. Reactivity toward nucleophilic acyl
substitution is determined by the leaving group ability and the
electrophilicity of the carbonyl carbon. Acid chlorides are the most
reactive because chloride is a good leaving group and the carbonyl
carbon is highly electrophilic. Anhydrides are less reactive than acid
chlorides but more reactive than esters. Esters are less reactive than
anhydrides but more reactive than amides. Amides are the least
reactive because nitrogen is a poor leaving group and the lone pair
on nitrogen donates into the carbonyl, reducing electrophilicity. The
correct order of increasing reactivity is Amide < Ester < Anhydride <
Acid Chloride (IV < III < II < I). Option A is incorrect because it reverses
the order. Option C is incorrect because it places anhydride before
acid chloride. Option D is incorrect because it places amide as the
most reactive .
Q3: Which of the following statements best explains why acid
chlorides are more reactive toward nucleophilic acyl substitution
than esters?
A) Chlorine is more electronegative than oxygen
B) The chloride ion is a better leaving group than alkoxide
C) Esters have stronger carbon-oxygen bonds
D) Acid chlorides are more sterically hindered
Rationale: The correct answer is B. In nucleophilic acyl substitution,
the leaving group departs after the tetrahedral intermediate is
formed. The ability of the leaving group to depart is a key factor in
determining reactivity. Chloride ion (Cl⁻) is a weak base and an
