Preparing for the ACS Organic Chemistry can feel overwhelming, especially when you’re unsure what kind of questions to expect on exam day. This practice test is designed to give you a realistic preview of the exam format while helping you strengthen your understanding of key concepts. Instead of just memorizing answers, you’ll get a chance to think through scenarios, improve your accuracy, and build confidence. Use this as part of your daily study routine to identify weak areas and gradually improve your performance.
Updated for 2026: This guide provides a structured approach to help you prepare effectively, understand key concepts, and practice real exam-level questions.
How to Use This Practice Test
- Start by reviewing key concepts before attempting questions
- Take the test in a timed environment
- Analyze your mistakes and revisit weak areas
Why This Practice Test Matters
This practice test is designed to simulate the real exam environment and help you identify knowledge gaps, improve accuracy, and build confidence.
| Exam Name | ACS Organic Chemistry Practice Exam |
|---|---|
| Exam Provider | American Chemical Society (ACS) |
| Exam Type | College-Level Organic Chemistry Standardized Assessment |
| Total Practice Questions | 90+ Practice Questions (Updated for 2026) |
| Coverage Topics | • Structure, Bonding & Hybridization • Reaction Mechanisms (SN1, SN2, E1, E2) • Alkanes, Alkenes, Alkynes & Aromatic Compounds • Functional Groups (Alcohols, Aldehydes, Ketones, Acids, Esters, Amines) • Oxidation–Reduction & Reagents • Stereochemistry & Isomerism |
| Question Format | Multiple Choice Questions (MCQs) – Conceptual + Mechanism-Based |
| Difficulty Level | Intermediate to Advanced (Aligned with Real ACS Organic Exam) |
| Study Tips | • Focus on reaction mechanisms, not memorization • Practice SN1/SN2/E1/E2 decision-making • Learn key reagents and their functions • Understand stereochemistry and carbocation stability |
| Best For | College students preparing for ACS Organic Chemistry exams |
| Updated | 2026 Latest Version |
1.
Which hybridization is present in methane (CH₄)?
A. sp
B. sp²
C. sp³
D. dsp³
Correct Answer: C
Explanation: Methane has four sigma bonds around carbon, requiring four equivalent hybrid orbitals. This leads to sp³ hybridization, producing a tetrahedral geometry with bond angles of about 109.5°, minimizing electron pair repulsion.
2.
Which functional group is present in alcohols?
A. –CHO
B. –COOH
C. –OH
D. –NH₂
Correct Answer: C
Explanation: Alcohols are characterized by the hydroxyl group (–OH) attached to a carbon atom. This group makes alcohols polar and capable of hydrogen bonding, influencing their boiling points and solubility.
3.
Which compound undergoes SN1 reaction most readily?
A. CH₃Cl
B. CH₃CH₂Cl
C. (CH₃)₃CCl
D. CH₃CH₂CH₂Cl
Correct Answer: C
Explanation: SN1 reactions proceed through carbocation intermediates. Tertiary carbocations are most stable due to hyperconjugation and inductive effects, making tert-butyl chloride most reactive.
4.
Which is the strongest acid?
A. CH₄
B. NH₃
C. H₂O
D. HF
Correct Answer: D
Explanation: HF is more acidic than water and ammonia due to its highly polar H–F bond. Although not the strongest acid overall, among the options it donates protons most readily.
5.
Which reaction forms an alkene from an alkyl halide?
A. Substitution
B. Elimination
C. Addition
D. Oxidation
Correct Answer: B
Explanation: Elimination reactions (E1 or E2) remove atoms from adjacent carbons, forming a double bond and producing an alkene.
6.
Which reagent is used for hydrogenation of alkenes?
A. H₂/Pd
B. KMnO₄
C. HCl
D. NaOH
Correct Answer: A
Explanation: Hydrogenation adds H₂ across a double bond in the presence of a metal catalyst like Pd, converting alkenes to alkanes.
7.
What is the major product of Markovnikov addition?
A. Hydrogen adds to carbon with fewer hydrogens
B. Hydrogen adds to carbon with more hydrogens
C. Halogen adds to carbon with more hydrogens
D. Random addition
Correct Answer: B
Explanation: Markovnikov’s rule states hydrogen attaches to the carbon with more hydrogens, forming the more stable carbocation intermediate.
8.
Which is aromatic?
A. Cyclobutane
B. Benzene
C. Cyclohexane
D. Ethane
Correct Answer: B
Explanation: Benzene is aromatic due to its planar ring and delocalized π electrons following Huckel’s rule (4n+2 π electrons).
9.
Which is a nucleophile?
A. H⁺
B. Cl⁻
C. BF₃
D. AlCl₃
Correct Answer: B
Explanation: Nucleophiles donate electron pairs. Cl⁻ has lone pairs and negative charge, making it a strong nucleophile.
10.
Which is an electrophile?
A. OH⁻
B. NH₃
C. H⁺
D. CH₃⁻
Correct Answer: C
Explanation: Electrophiles accept electrons. H⁺ is electron-deficient and seeks electron pairs, making it a strong electrophile.
11.
Which reaction type is addition?
A. Alkane → Alkene
B. Alkene → Alkane
C. Alcohol → Alkene
D. Ester → Acid
Correct Answer: B
Explanation: Addition reactions add atoms across a double bond, converting alkenes into alkanes.
12.
Which is a ketone?
A. CH₃CHO
B. CH₃COCH₃
C. CH₃OH
D. CH₃COOH
Correct Answer: B
Explanation: Ketones contain a carbonyl group bonded to two carbons. CH₃COCH₃ (acetone) is a classic example.
13.
Which is an aldehyde?
A. CH₃CHO
B. CH₃COCH₃
C. CH₃OH
D. CH₄
Correct Answer: A
Explanation: Aldehydes have a carbonyl group at the end of a chain, bonded to at least one hydrogen.
14.
Which is strongest nucleophile?
A. H₂O
B. NH₃
C. OH⁻
D. CH₄
Correct Answer: C
Explanation: OH⁻ has a negative charge and lone pairs, making it highly reactive as a nucleophile.
15.
Which is E2 reaction characteristic?
A. Two-step
B. Carbocation intermediate
C. One-step
D. Rearrangement
Correct Answer: C
Explanation: E2 is a concerted, one-step reaction without intermediates.
16.
Which compound is chiral?
A. CH₄
B. CCl₄
C. CHBrClF
D. CO₂
Correct Answer: C
Explanation: A carbon with four different substituents is chiral.
17.
Which is oxidation?
A. Gain of H
B. Loss of O
C. Gain of O
D. Gain of electrons
Correct Answer: C
Explanation: Oxidation involves gain of oxygen or loss of hydrogen.
18.
Which is reduction?
A. Gain of O
B. Loss of H
C. Gain of H
D. Loss of electrons
Correct Answer: C
Explanation: Reduction involves gain of hydrogen or electrons.
19.
Which reagent oxidizes alcohol to aldehyde?
A. PCC
B. H₂
C. NaBH₄
D. LiAlH₄
Correct Answer: A
Explanation: PCC oxidizes primary alcohols to aldehydes without further oxidation.
20.
Which is strongest base?
A. H₂O
B. NH₃
C. OH⁻
D. Cl⁻
Correct Answer: C
21.
Which has highest boiling point?
A. Methane
B. Ethane
C. Ethanol
D. Propane
Correct Answer: C
Explanation: Ethanol forms hydrogen bonds, increasing boiling point.
22.
Which is alkene formula?
A. CnH2n+2
B. CnH2n
C. CnH2n-2
D. CnHn
Correct Answer: B
23.
Which is alkyne?
A. Ethene
B. Ethyne
C. Ethane
D. Methane
Correct Answer: B
24.
Which reaction forms alcohol?
A. Addition of H₂O
B. Elimination
C. Substitution
D. Oxidation
Correct Answer: A
25.
Which is ester group?
A. –COOH
B. –COOR
C. –CHO
D. –OH
Correct Answer: B
26.
Which is amine?
A. –OH
B. –NH₂
C. –COOH
D. –CHO
Correct Answer: B
27.
Which is SN2 feature?
A. Carbocation
B. Two-step
C. One-step backside attack
D. Rearrangement
Correct Answer: C
28.
Which is anti-Markovnikov?
A. HBr + peroxide
B. HCl
C. H₂O
D. H₂
Correct Answer: A
29.
Which is aromatic rule?
A. 4n
B. 4n+2
C. 2n
D. n²
Correct Answer: B
30.
Which is strongest IMF in alcohol?
A. Dispersion
B. Dipole
C. Hydrogen bonding
D. Ionic
Correct Answer: C
31.
Which substrate reacts fastest in an SN2 reaction?
A. (CH₃)₃CBr
B. CH₃Br
C. CH₃CH₂Br
D. (CH₃)₂CHBr
Correct Answer: B
Explanation: SN2 reactions proceed via backside attack and are highly sensitive to steric hindrance. Methyl bromide (CH₃Br) has minimal steric hindrance, allowing nucleophiles to attack easily, making it the fastest among the given options.
32.
Which carbocation is most stable?
A. Primary
B. Secondary
C. Tertiary
D. Methyl
Correct Answer: C
Explanation: Tertiary carbocations are stabilized by hyperconjugation and inductive effects from three alkyl groups. These effects distribute positive charge more effectively, making them more stable than secondary, primary, or methyl carbocations.
33.
Which reaction mechanism involves carbocation rearrangement?
A. SN2
B. E2
C. SN1
D. Addition
Correct Answer: C
Explanation: SN1 reactions proceed through carbocation intermediates, which can rearrange (hydride or methyl shifts) to form more stable carbocations. This is a key feature distinguishing SN1 from SN2 mechanisms.
34.
Which solvent favors SN2 reactions?
A. Polar protic
B. Nonpolar
C. Polar aprotic
D. Acidic
Correct Answer: C
Explanation: Polar aprotic solvents (like DMSO or acetone) do not strongly solvate nucleophiles, allowing them to remain reactive. This enhances nucleophilicity and favors SN2 reactions over SN1.
35.
Which reagent is used for oxidation of secondary alcohols?
A. PCC
B. KMnO₄
C. NaBH₄
D. H₂
Correct Answer: B
Explanation: Strong oxidizing agents like KMnO₄ convert secondary alcohols into ketones. PCC can also oxidize, but KMnO₄ is more commonly associated with strong oxidation conditions in ACS-level questions.
36.
Which compound shows geometric isomerism?
A. Ethane
B. Ethene
C. Propane
D. Methane
Correct Answer: B
Explanation: Ethene (alkene) has restricted rotation around the double bond, allowing cis-trans (geometric) isomerism. Alkanes freely rotate and do not show this property.
37.
Which functional group is present in carboxylic acids?
A. –COOH
B. –OH
C. –CHO
D. –NH₂
Correct Answer: A
Explanation: Carboxylic acids contain the –COOH group, combining a carbonyl (C=O) and hydroxyl (–OH), giving them acidic properties.
38.
Which reaction converts alkene to alcohol?
A. Hydrogenation
B. Hydrohalogenation
C. Hydration
D. Oxidation
Correct Answer: C
Explanation: Hydration adds water across a double bond, forming alcohols. It follows Markovnikov’s rule unless special conditions apply.
39.
Which intermediate forms in E1 reactions?
A. Radical
B. Carbocation
C. Carbanion
D. Ion pair
Correct Answer: B
Explanation: E1 reactions proceed via carbocation intermediates, similar to SN1, allowing rearrangements.
40.
Which is strongest nucleophile in protic solvent?
A. F⁻
B. Cl⁻
C. Br⁻
D. I⁻
Correct Answer: D
Explanation: In protic solvents, larger ions like I⁻ are less solvated and more nucleophilic than smaller ions like F⁻.
41.
Which is aromatic compound?
A. Cyclobutadiene
B. Benzene
C. Cyclooctatetraene
D. Cyclopropane
Correct Answer: B
Explanation: Benzene satisfies Huckel’s rule (4n+2 π electrons) and is planar, making it aromatic.
42.
Which reagent reduces ketone to alcohol?
A. PCC
B. KMnO₄
C. NaBH₄
D. HCl
Correct Answer: C
Explanation: NaBH₄ donates hydride ions to reduce ketones into secondary alcohols.
43.
Which has highest acidity?
A. Alcohol
B. Carboxylic acid
C. Alkane
D. Amine
Correct Answer: B
Explanation: Carboxylic acids are more acidic due to resonance stabilization of their conjugate base.
44.
Which bond is strongest?
A. C–C
B. C=C
C. C≡C
D. C–H
Correct Answer: C
Explanation: Triple bonds have highest bond energy due to three shared electron pairs.
45.
Which is electrophile in reaction?
A. OH⁻
B. NH₃
C. H⁺
D. CH₃⁻
Correct Answer: C
46.
Which is product of complete combustion?
A. CO
B. CO₂ + H₂O
C. C + H₂
D. CO₂ only
Correct Answer: B
47.
Which compound has highest boiling point?
A. Alkane
B. Alkene
C. Alcohol
D. Ether
Correct Answer: C
48.
Which is SN2 stereochemistry?
A. Retention
B. Inversion
C. Racemization
D. No change
Correct Answer: B
49.
Which reaction gives racemic mixture?
A. SN2
B. E2
C. SN1
D. Addition
Correct Answer: C
50.
Which is most stable alkene?
A. Mono-substituted
B. Di-substituted
C. Tri-substituted
D. Tetra-substituted
Correct Answer: D
51.
Which is conjugated system?
A. Single bonds only
B. Alternating double bonds
C. Triple bonds only
D. Random bonds
Correct Answer: B
52.
Which is Markovnikov addition?
A. H to less substituted
B. H to more substituted
C. Random
D. No rule
Correct Answer: B
53.
Which is strongest base?
A. Cl⁻
B. NH₃
C. OH⁻
D. H₂O
Correct Answer: C
54.
Which is resonance structure feature?
A. Atoms move
B. Electrons move
C. Bonds break
D. Energy changes
Correct Answer: B
55.
Which is oxidation?
A. Gain electrons
B. Lose electrons
C. Gain H
D. Lose O
Correct Answer: B
56.
Which is reduction?
A. Lose electrons
B. Gain electrons
C. Lose H
D. Gain O
Correct Answer: B
57.
Which is functional group of ester?
A. –COOH
B. –COOR
C. –OH
D. –NH₂
Correct Answer: B
58.
Which is planar molecule?
A. sp³
B. sp²
C. sp
D. dsp³
Correct Answer: B
59.
Which reaction forms polymer?
A. Addition
B. Elimination
C. Substitution
D. Oxidation
Correct Answer: A
60.
Which IMF strongest in alcohol?
A. Dispersion
B. Dipole
C. Hydrogen bonding
D. Ionic
Correct Answer: C
61.
Which alkene is most stable?
A. CH₂=CH₂
B. CH₃CH=CH₂
C. CH₃CH=CHCH₃
D. (CH₃)₂C=C(CH₃)₂
Correct Answer: D
Explanation: Alkene stability increases with substitution due to hyperconjugation and inductive effects. Tetrasubstituted alkenes have the greatest electron donation from alkyl groups, stabilizing the double bond more effectively than mono-, di-, or tri-substituted alkenes.
62.
Which carbocation rearrangement is most common?
A. Proton transfer
B. Hydride shift
C. Electron transfer
D. Bond rotation
Correct Answer: B
Explanation: Hydride shifts occur when a hydrogen atom with its bonding electrons moves to an adjacent carbocation center, forming a more stable carbocation. This is commonly seen in SN1 and E1 mechanisms to achieve greater stability.
63.
Which reagent performs anti-Markovnikov addition of HBr?
A. HBr only
B. HBr + peroxide
C. HCl
D. H₂O
Correct Answer: B
Explanation: In the presence of peroxides, HBr adds via a radical mechanism, leading to anti-Markovnikov addition where bromine attaches to the less substituted carbon.
64.
Which functional group is most reactive toward nucleophilic addition?
A. Alkane
B. Alkene
C. Aldehyde
D. Ether
Correct Answer: C
Explanation: Aldehydes are highly reactive due to the polar carbonyl group and less steric hindrance compared to ketones. This makes them more susceptible to nucleophilic attack.
65.
Which conformation of ethane is most stable?
A. Eclipsed
B. Staggered
C. Planar
D. Twisted
Correct Answer: B
Explanation: The staggered conformation minimizes torsional strain by maximizing distance between electron pairs, making it the lowest energy and most stable conformation of ethane.
66.
Which is strongest acid?
A. Phenol
B. Ethanol
C. Acetic acid
D. Methane
Correct Answer: C
Explanation: Acetic acid is strongest due to resonance stabilization of its conjugate base (acetate ion), which distributes negative charge over two oxygen atoms.
67.
Which compound undergoes fastest E2 reaction?
A. Primary halide
B. Secondary halide
C. Tertiary halide
D. Methyl halide
Correct Answer: C
Explanation: E2 reactions favor tertiary substrates because steric hindrance discourages substitution, and elimination becomes more favorable.
68.
Which intermediate forms in radical reactions?
A. Carbocation
B. Carbanion
C. Radical
D. Ion
Correct Answer: C
Explanation: Radical reactions involve species with unpaired electrons, making radicals highly reactive intermediates.
69.
Which is strongest nucleophile in aprotic solvent?
A. F⁻
B. Cl⁻
C. Br⁻
D. I⁻
Correct Answer: A
Explanation: In polar aprotic solvents, smaller ions like F⁻ are less solvated and more reactive, making them stronger nucleophiles compared to larger halides.
70.
Which reaction converts alcohol to alkene?
A. Substitution
B. Addition
C. Elimination
D. Oxidation
Correct Answer: C
Explanation: Dehydration of alcohol removes water, forming an alkene via elimination.
71.
Which compound shows resonance?
A. CH₄
B. CO₂
C. Benzene
D. Ethane
Correct Answer: C
Explanation: Benzene has delocalized π electrons across its ring, resulting in resonance stabilization.
72.
Which reagent reduces aldehyde to alcohol?
A. PCC
B. KMnO₄
C. NaBH₄
D. HCl
Correct Answer: C
Explanation: NaBH₄ donates hydride ions, reducing aldehydes to primary alcohols.
73.
Which is most acidic hydrogen?
A. Alkane
B. Alcohol
C. Carboxylic acid
D. Alkene
Correct Answer: C
Explanation: Carboxylic acids have acidic protons due to resonance stabilization of conjugate base.
74.
Which bond rotates freely?
A. Double
B. Triple
C. Single
D. Aromatic
Correct Answer: C
Explanation: Single bonds allow free rotation, unlike double or triple bonds.
75.
Which is electrophilic aromatic substitution?
A. SN1
B. E2
C. Benzene nitration
D. Addition
Correct Answer: C
Explanation: Nitration introduces NO₂ group via electrophilic substitution.
76.
Which is most stable conformation of butane?
A. Eclipsed
B. Gauche
C. Anti
D. Planar
Correct Answer: C
Explanation: Anti conformation places methyl groups opposite, minimizing steric strain.
77.
Which is conjugated diene?
A. CH₂=CH–CH=CH₂
B. CH₂=CH₂
C. CH₃CH₃
D. CH≡CH
Correct Answer: A
78.
Which reaction uses catalyst Pd/C?
A. Oxidation
B. Hydrogenation
C. Substitution
D. Elimination
Correct Answer: B
79.
Which is strongest IMF in carboxylic acids?
A. Dispersion
B. Dipole
C. Hydrogen bonding
D. Ionic
Correct Answer: C
80.
Which forms ester?
A. Alcohol + acid
B. Alkane + alkene
C. Ether + water
D. Alcohol + base
Correct Answer: A
81.
Which is planar molecule?
A. sp³
B. sp²
C. sp
D. dsp³
Correct Answer: B
82.
Which reaction gives alkane?
A. Hydrogenation
B. Elimination
C. Oxidation
D. Substitution
Correct Answer: A
83.
Which is strongest base?
A. Cl⁻
B. OH⁻
C. NH₃
D. H₂O
Correct Answer: B
84.
Which is anti addition?
A. Hydrogenation
B. Halogenation
C. Hydration
D. Oxidation
Correct Answer: B
85.
Which is leaving group?
A. OH⁻
B. Br⁻
C. NH₃
D. CH₄
Correct Answer: B
86.
Which is aromatic rule?
A. 4n
B. 4n+2
C. n²
D. 2n
Correct Answer: B
87.
Which is reduction?
A. Gain electrons
B. Lose electrons
C. Gain O
D. Lose H
Correct Answer: A
88.
Which is oxidation?
A. Gain H
B. Lose electrons
C. Gain electrons
D. Lose O
Correct Answer: B
89.
Which is SN1 feature?
A. One-step
B. Carbocation
C. Inversion
D. No rearrangement
Correct Answer: B
90.
Which is SN2 feature?
A. Two-step
B. Carbocation
C. Inversion
D. Rearrangement
Correct Answer: C
Frequently Asked Questions
Is this ACS Organic Chemistry practice test similar to the real exam?
Yes, this practice test is designed to reflect real exam patterns, structure, and difficulty level to help you prepare effectively.
What is the best way to use this ACS Organic Chemistry test for preparation?
Take the test in a timed setting, review your answers carefully, and focus on improving weak areas after each attempt.
Can I retake this ACS Organic Chemistry practice test multiple times?
Yes, repeating the test helps reinforce concepts, improve accuracy, and build confidence for the actual exam.
Is this ACS Organic Chemistry test useful for first-time candidates?
This practice test is suitable for both beginners and retakers who want to improve their understanding and performance.