halogen derivatives MHT-CET Exam Test - 1

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1. In the IUPAC nomenclature, which name correctly describes a straight‑chain saturated haloalkane with three carbon atoms in a row, where the chlorine atom is bonded to the first carbon?

A) 1-Chloropropane

B) Chloropropane

C) 2-Chloropropane

D) Propyl chloride

Explanation: The correct IUPAC name is 1-chloropropane; “propyl chloride” is a common name for the same compound.

2. The systematic name of the haloalkane CH₃–CHCl–CH₂–CH₃, according to IUPAC rules considering lowest locant and parent chain selection, is:

A) 1-Chlorobutane

B) sec-Butyl chloride

C) 2-Chlorobutane

D) Butyl chloride

Explanation: Substituent at the second carbon of a four‑carbon chain gives 2‑chlorobutane; other options are common names or incorrect locants.

3. Which of the following alkyl halides contains a halogen atom attached to a carbon atom that is itself directly bonded to three other carbon atoms?

A) 2-Bromobutane

B) Bromomethane

C) 1-Bromobutane

D) 2-Bromo-2-methylpropane

Explanation: In 2‑bromo‑2‑methylpropane, the C–Br carbon is tertiary (bonded to three other carbons).

4. Which compound has its halogen atom attached to a carbon atom that is adjacent to a carbon–carbon double bond (allylic position)?

A) CH₂=CH–CH₂–Cl

B) C₆H₅–Cl

C) CH₂Cl₂

D) CH₃–CH₂–Cl

Explanation: CH₂=CH–CH₂–Cl is an allylic chloride; the halogen is on the carbon next to the C=C.

5. In which of the following compounds is the carbon–halogen bond directly connected to an sp²‑hybridized carbon atom of a C=C double bond?

A) CH₂=CH–CH₂–Cl

B) C₆H₅–CH₂–Cl

C) CH₂=CH–Cl

D) CH₃–CH₂–Cl

Explanation: In vinyl chloride (CH₂=CH–Cl), the C–Cl bond is to an sp² carbon of the double bond.

6. In CH₃–Cl, the carbon atom bonded to chlorine is hybridized as:

A) dsp²

B) sp

C) sp³

D) sp²

Explanation: Methane‑like carbon with four sigma bonds is sp³‑hybridized.

7. Considering bond strength trends for C–X bonds (X = F, Cl, Br, I), the maximum bond dissociation energy is found in:

A) C–I

B) C–Br

C) C–Cl

D) C–F

Explanation: The C–F bond is the strongest among common C–halogen bonds due to short bond length and high polarity.

8. At standard temperature and pressure, which methyl halide exists as a liquid and not as a gas?

A) Methyl iodide (CH₃I)

B) Methyl bromide (CH₃Br)

C) Methyl chloride (CH₃Cl)

D) Methyl fluoride (CH₃F)

Explanation: CH₃I (bp ≈ 42 °C) is a liquid at room temperature; CH₃F/Cl/Br are gases near STP.

9. Which member of the methyl halide series has the highest boiling point due to London dispersion forces and molecular mass?

A) CH₃I

B) CH₃Br

C) CH₃F

D) CH₃Cl

Explanation: Boiling point increases with molar mass and polarizability: CH₃I > CH₃Br > CH₃Cl > CH₃F.

10. Haloalkanes, due to differences in electronegativity between carbon and halogen, are generally:

A) Non-polar

B) Ionic

C) Polar

D) All of these

Explanation: The C–X bond is polarized (Cδ⁺–Xδ⁻), so most haloalkanes are polar molecules.

11. The reaction of an alcohol with thionyl chloride (SOCl₂) in the presence of pyridine predominantly yields:

A) Alkyl chloride

B) Alkyl bromide

C) Alkyl iodide

D) Alkyl fluoride

Explanation: SOCl₂ in pyridine converts alcohols into alkyl chlorides efficiently with gaseous byproducts.

12. The laboratory conversion of CH₃CH₂Cl to CH₃CH₂I using NaI in dry acetone is an example of:

A) Wurtz reaction

B) Cannizzaro reaction

C) Finkelstein reaction

D) Kolbe’s reaction

Explanation: Halide exchange (Cl → I) in acetone is the Finkelstein reaction.

13. The transformation of methane to chloromethane in the presence of UV light by substitution is known as:

A) Halogen exchange

B) Dehydrohalogenation

C) Photochemical halogenation

D) Hydrohalogenation

Explanation: UV light initiates radical substitution, called photochemical halogenation.

14. Which reaction involves coupling of two alkyl halides using sodium metal in dry ether to form higher alkanes?

A) Wurtz reaction

B) Saytzeff reaction

C) Friedel–Crafts alkylation

D) Kolbe electrolysis

Explanation: Wurtz reaction couples alkyl halides in the presence of Na/ether.

15. Allyl chloride can be synthesized from propene by addition of chlorine under specific low‑temperature UV light conditions via:

A) Cl₂ in CCl₄

B) Cl₂ in sunlight

C) Cl₂ with peroxide

D) Cl₂ under UV at low temperature

Explanation: Allylic substitution occurs with Cl₂ under UV light at low temperatures.

16. Which alkyl halide undergoes nucleophilic substitution by the SN1 mechanism at the fastest rate?

A) Allyl chloride

B) Methyl chloride

C) tert-Butyl chloride

D) Ethyl chloride

Explanation: Tertiary carbocations are most stable, so tert‑butyl chloride undergoes SN1 fastest.

17. The correct decreasing order of reactivity of alkyl halides towards SN2 mechanism is:

A) 1° > 2° > 3°

B) 3° > 2° > 1°

C) 3° > 1° > 2°

D) 2° > 1° > 3°

Explanation: SN2 rate decreases with steric hindrance: primary > secondary > tertiary.

18. The major organic product of CH₃CH₂Cl treated with aqueous KOH is:

A) Ethyl chloride

B) Ethene

C) Ethyl ether

D) Ethanol

Explanation: Hydrolysis of ethyl chloride with aqueous KOH gives ethanol.

19. Benzyl chloride reacts with aqueous sodium hydroxide to form:

A) Toluene

B) Benzaldehyde

C) Benzyl alcohol

D) Phenol

Explanation: Nucleophilic substitution of benzyl chloride gives benzyl alcohol.

20. The low reactivity of chlorobenzene towards nucleophilic substitution is primarily due to:

A) High electronegativity of chlorine

B) Weak C–Cl bond

C) High polarity of the bond

D) Resonance stabilization

Explanation: The C–Cl bond in chlorobenzene is stabilized by resonance, reducing nucleophilic substitution reactivity.

21. Which alkyl halide shows the highest reactivity in E2 elimination due to formation of the most stable alkene?

A) 1° alkyl halide

B) 3° alkyl halide

C) Methyl halide

D) 2° alkyl halide

Explanation: Tertiary halides form the most stable alkenes upon elimination, hence react fastest in E2.

22. On heating 2-bromopentane with alcoholic KOH, the major product formed is:

A) Pentane

B) Pent-2-ene

C) Pentanol

D) Pent-1-ene

Explanation: Alcoholic KOH induces elimination, major alkene follows Saytzeff’s rule: pent-2-ene.

23. Which rule is applied to predict that the most substituted alkene will be the major product in elimination reactions?

A) Le Chatelier’s principle

B) Markovnikov’s rule

C) Raoult’s law

D) Saytzeff’s rule

Explanation: Saytzeff’s rule predicts formation of the more substituted and stable alkene.

24. The treatment of an alkyl halide with alcoholic silver nitrate results in the formation of:

A) Aldehyde

B) Ether

C) Alcohol

D) Alkene

Explanation: Alcoholic AgNO₃ promotes elimination of HX, yielding alkene.

25. Dehydrohalogenation of alkyl halides is generally carried out using:

A) Alcoholic KOH

B) Aqueous KOH

C) NaCl

D) NaOH

Explanation: Alcoholic KOH abstracts β-hydrogen, effecting dehydrohalogenation to form alkenes.

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