Quiz: CBSE Organic Chemistry Reactions — 24 questions

1. Which content should receive priority in a last-minute CBSE Class 12 Chemistry revision handbook?

A. Quantitative derivations, research methods, and spectroscopy interpretation

B. Historical development of chemistry, laboratory safety, and industrial economics

C. Advanced reaction mechanisms, orbital theory, and university-level synthesis

D. Chemical reactions, preparations, named reactions, tests, and conversions

Answer: (D)

Explanation

The handbook is designed for rapid CBSE Class 12 revision, so it prioritizes reaction-based examination content such as preparations, tests, reagents, products, and conversions. Advanced mechanisms are outside its intended scope because they belong to a more advanced level of study.

2. A student preparing for a CBSE Class 12 examination should approach the material in which way?

A. By practicing direct reactions, product prediction, reagents, conversions, and distinguishing tests

B. By concentrating on detailed university-level mechanisms and mathematical reaction models

C. By studying industrial process design in place of NCERT-level reaction questions

D. By memorizing historical discoveries while postponing reaction-based problem solving

Answer: (A)

Explanation

CBSE-level revision emphasizes direct reaction questions, product prediction, reagent identification, conversions, distinguishing tests, and assertion-reasoning items. Detailed university-level mechanism study is not the intended focus and would not match the stated examination level.

3. What information should accompany an important chemical reaction in an exam-focused handbook?

A. Its name when applicable, general equation, example, conditions, explanation, and key point

B. Its balanced equation followed by a historical note about the reaction's discovery

C. Its molecular formula, physical state, boiling point, and industrial production statistics

D. Its mechanism alone, without a worked example, reagent, condition, or examination note

Answer: (A)

Explanation

The required format combines the reaction name, general equation, actual example, reagent or condition, short explanation, and an exam-focused point. Presenting an equation without conditions and chemical meaning does not satisfy this format.

4. How should an open-chain alcohol such as ethanol be represented in a properly formatted condensed structural formula?

A. C₂H₅ with the hydroxyl group omitted from the structure

B. A benzene ring bearing an OH substituent

C. CH3CH2OH with all numerical indices written on the line

D. CH₃CH₂OH with the hydroxyl group clearly visible

Answer: (D)

Explanation

Open-chain compounds should use condensed structural formulas with clearly visible functional groups, so ethanol is written as CH₃CH₂OH. A benzene-ring representation is inappropriate for an aliphatic open-chain compound, while omitting the hydroxyl group hides essential structural information.

5. Which representation follows the required formatting rule for numerical indices in chemical formulas?

A. H2O

B. CH3COOH

C. CH₃COOH

D. C6H5Cl

Answer: (C)

Explanation

Every numerical index must appear as a proper subscript, making CH₃COOH the correctly formatted representation. The alternatives place one or more indices on the baseline rather than using subscripts.

6. How should a reaction involving chlorobenzene be displayed when the relative positions of substituents are relevant?

A. With a molecular formula that gives atom counts but omits the ring structure

B. With a recognizable benzene ring and clearly marked ortho, meta, or para positions

C. With a condensed open-chain formula that places all substituents in one sequence

D. With a skeletal chain diagram that does not distinguish aromatic substitution positions

Answer: (B)

Explanation

Aromatic reactions must show a recognizable benzene ring with attached substituents and clear relative positions when needed. Condensed open-chain formulas and molecular formulas cannot adequately display the aromatic ring or distinguish ortho, meta, and para arrangements.

7. Which preparation route is specifically relevant to the haloalkanes and haloarenes chapter?

A. Preparing haloalkanes through peptide hydrolysis and haloarenes through carbohydrate fermentation

B. Preparing haloalkanes from alcohols or hydrocarbons and haloarenes by aromatic electrophilic substitution

C. Preparing haloalkanes from amines and haloarenes through aldehyde condensation

D. Preparing haloalkanes by esterification and haloarenes through nucleic-acid replication

Answer: (B)

Explanation

The chapter covers preparation of haloalkanes from alcohols and hydrocarbons, along with relevant halogenation methods, and preparation of haloarenes by aromatic electrophilic substitution. The other routes describe unrelated reaction classes and do not represent the stated preparation coverage.

8. Which named reaction combines an alkyl halide with an aryl halide to form an alkyl-substituted aromatic compound?

A. Swarts reaction

B. Fittig reaction

C. Wurtz reaction

D. Wurtz–Fittig reaction

Answer: (D)

Explanation

The Wurtz–Fittig reaction combines alkyl and aryl halides, producing an alkyl-substituted aromatic compound. Wurtz couples alkyl halides, Fittig couples aryl halides, and Swarts is associated with halogen exchange rather than this carbon–carbon coupling.

9. When a haloalkane is heated with alcoholic KOH and an alkene forms according to Saytzeff orientation, what type of transformation has occurred?

A. Nucleophilic substitution replacing halogen with a nucleophile

B. Halogen exchange converting one carbon–halogen bond into another

C. Aromatic electrophilic substitution on a benzene ring

D. Dehydrohalogenation through elimination of hydrogen halide

Answer: (D)

Explanation

Alcoholic KOH promotes dehydrohalogenation, an elimination process that removes hydrogen halide and forms an alkene, commonly following Saytzeff product preference. Nucleophilic substitution instead replaces the halogen with a nucleophile and does not describe the alkene-forming change here.

10. Which preparation route converts an alkene into an alcohol by adding the elements of water across the carbon–carbon double bond?

A. Williamson ether synthesis

B. Friedel–Crafts acylation

C. Acid-catalyzed hydration

D. Rosenmund reduction

Answer: (C)

Explanation

Acid-catalyzed hydration adds water across an alkene to produce an alcohol. Rosenmund reduction forms aldehydes, Williamson synthesis forms ethers, and Friedel–Crafts acylation forms ketones.

11. What type of product is generally formed when an alcohol undergoes dehydration under suitable conditions?

A. A carboxylic acid

B. An alkene

C. An aromatic ether

D. An alkyl chloride

Answer: (B)

Explanation

Alcohol dehydration eliminates water and forms an alkene. Oxidation, rather than dehydration, produces carbonyl or carboxylic-acid products depending on the alcohol and reaction conditions.

12. Which reaction is characteristic of phenol because its hydroxyl group is attached to a benzene ring?

A. Reaction with sodium hydroxide to form sodium phenoxide

B. Conversion into an alkene by acid-catalyzed dehydration

C. Formation of an alkyl halide with phosphorus pentachloride

D. Reaction with sodium bicarbonate to release carbon dioxide

Answer: (A)

Explanation

Phenol reacts with sodium hydroxide to form sodium phenoxide because its aromatic hydroxyl group is sufficiently acidic. Sodium bicarbonate is associated with carboxylic acids, while dehydration and phosphorus pentachloride reactions describe other alcohol chemistry.

13. Which named method prepares an aldehyde by controlled reduction of an acyl chloride?

A. Friedel–Crafts acylation

B. Clemmensen reduction

C. Wolff–Kishner reduction

D. Rosenmund reduction

Answer: (D)

Explanation

Rosenmund reduction converts an acyl chloride into an aldehyde through controlled hydrogenation. Clemmensen and Wolff–Kishner reductions convert carbonyl compounds into hydrocarbons, while Friedel–Crafts acylation is a ketone-preparation method.

14. Which reaction is specifically classified as a method for preparing ketones?

A. Gattermann–Koch formylation

B. Friedel–Crafts acylation

C. Etard reaction

D. Stephen reaction

Answer: (B)

Explanation

Friedel–Crafts acylation introduces an acyl group into an aromatic ring and produces an aromatic ketone. The Stephen, Etard, and Gattermann–Koch methods are associated with aldehyde preparation.

15. Why can aldehydes and ketones both react with hydrogen cyanide?

A. Their carbon chains eliminate water to form aromatic rings

B. Their carbonyl oxygen acts as a leaving group in oxidation

C. Their hydroxyl group readily undergoes electrophilic substitution

D. Their carbonyl carbon is electrophilic and undergoes nucleophilic addition

Answer: (D)

Explanation

The polar carbonyl group has an electrophilic carbon atom, allowing cyanide ion to add nucleophilically to both aldehydes and ketones. The other choices describe processes that do not account for HCN addition to carbonyl compounds.

16. Which reaction reduces the carbonyl group of an aldehyde or ketone to a methylene group under strongly acidic conditions?

A. Aldol condensation

B. Cannizzaro reaction

C. Haloform reaction

D. Clemmensen reduction

Answer: (D)

Explanation

Clemmensen reduction converts aldehydes and ketones into hydrocarbons using zinc amalgam in strongly acidic conditions. Cannizzaro gives disproportionation of suitable aldehydes, aldol condensation forms larger carbonyl compounds, and haloform reactions produce haloform from suitable methyl ketones.

17. Which test identifies many aldehydes by producing a silver mirror?

A. 2,4-DNP test

B. Sodium bicarbonate test

C. Iodoform test

D. Tollens' test

Answer: (D)

Explanation

Tollens' reagent is reduced by many aldehydes to metallic silver, producing a silver mirror and establishing the presence of an aldehyde. The 2,4-DNP test detects carbonyl compounds through a precipitate, while the other tests identify different functional groups.

18. What information must accompany an observation such as effervescence for an organic test to establish a reliable identification?

A. The observation, melting point, boiling point, and molecular mass

B. The compound name, physical state, density, and storage conditions

C. The solvent, color of the container, temperature, and sample volume

D. The tested substance, reagent, reaction, observation, and identity established

Answer: (D)

Explanation

A complete organic test records the substance tested, reagent, chemical reaction, observation, and identity established; effervescence alone does not identify the compound. Physical properties and storage details may be useful elsewhere but do not provide the required test format.

19. How should an important organic conversion be presented to preserve its chemically significant steps?

A. As a sequence listing the starting compound and final product while grouping intermediate stages under one reaction arrow

B. As a summary table naming the conversion and product without displaying the order of the transformations

C. As a reaction scheme showing the main reagent and product while leaving routine intermediates to the reader

D. As a sequence showing the starting compound, each reagent or condition, every important intermediate, and the final product

Answer: (D)

Explanation

A complete conversion displays the starting compound, reagents or conditions, important intermediates, and final product in sequence. A scheme that groups or omits an important intermediate is incomplete because it hides part of the transformation pathway.

20. Which group of organic-compound chapters should be represented in an important-conversions collection?

A. Solutions and electrochemistry; chemical kinetics and surface chemistry; metallurgy

B. Amines and biomolecules; polymers and chemistry in everyday life; coordination compounds

C. Thermodynamics and equilibrium; p-block elements and hydrogen; environmental chemistry

D. Haloalkanes and haloarenes; alcohols, phenols and ethers; aldehydes, ketones and carboxylic acids

Answer: (D)

Explanation

The specified collection covers conversions from haloalkanes and haloarenes, alcohols, phenols and ethers, and aldehydes, ketones and carboxylic acids. The other choices name different chemistry groupings and do not identify the required conversion sections.

21. Which reaction belongs in a named-reactions quick-revision section for organic chemistry?

A. Hess law

B. Finkelstein reaction

C. Raoult law

D. Le Chatelier principle

Answer: (B)

Explanation

Finkelstein is one of the named organic reactions included in the quick-revision list. The other choices are principles or laws from physical chemistry rather than members of that named-reaction set.

22. What information should a reagents-at-a-glance table provide for each organic reaction?

A. The reaction, reagent, condition, and main product or result

B. The reactant formula, textbook chapter, preparation cost, and storage duration

C. The product name, industrial use, author reference, and page location

D. The reaction name, historical origin, laboratory hazard, and molecular mass

Answer: (A)

Explanation

The table is designed for rapid revision, so it pairs each reaction with its reagent, condition, and main product or result. Historical, logistical, or bibliographic details do not provide the required reaction-reference information.

23. Which set of checks belongs to the final quality-control review of an organic chemistry booklet?

A. Author biography, publication history, citation format, marketing language, index style, and printing cost

B. Chapter length, classroom schedule, laboratory inventory, student attendance, exam dates, and grading policy

C. Reactants, products, reagents, conditions, catalysts, temperatures, formulas, functional groups, and aromatic positions

D. Font color, decorative borders, illustration style, cover balance, binding type, and paper texture

Answer: (C)

Explanation

The final review must verify both chemical content and document completeness, including reaction components, conditions, formulas, functional groups, and aromatic positions. Decorative or administrative features may matter elsewhere, but they do not replace the specified chemical accuracy checks.

24. Which design choice best supports scanability and professional presentation in the booklet?

A. Reducing white space and shrinking reaction equations so that more content fits on each page

B. Adding dense decorative graphics around reactions and compressing several complicated schemes into each available page

C. Using chapter dividers, clear headings, large reaction equations, consistent typography, tables, and reagent or condition boxes

D. Using varied typefaces for every chapter and replacing tables with long paragraphs of uninterrupted explanation

Answer: (C)

Explanation

Chapter dividers, clear headings, readable equations, consistent typography, tables, and reagent or condition boxes help readers scan and navigate the material. Crowded reactions, excessive decoration, inconsistent typography, and reduced readability conflict with the required design principles.