Class 12 Haloalkanes and Haloarenes Mock Test (CBSE)

Topics in Haloalkanes and Haloarenes

• Classification of halogen compounds
• Nomenclature
• Nature of C-X bond
• Methods of preparation of haloalkanes
• Preparation of haloarenes
• Physical properties
• Nucleophilic substitution: SN1 and SN2
• Stereochemical aspects and optical isomerism
• Elimination reactions
• Reactions of haloarenes
• Polyhalogen compounds

Haloalkanes and Haloarenes practice questions with answers

1. Q1Multiple choice·1 mark
   Which of the following polyhalogen compounds is commonly used as a refrigerant in refrigerators and air conditioners?

   1. (a)$CHI_3$
   2. (b)$CCl_2F_2$
   3. (c)$CCl_4$
   4. (d)$CHCl_3$
   Show answer and step marks

   1. Correct option: (b) $CCl_2F_2$+1

   Answer: (b)
2. Q2Multiple choice·1 mark
   According to a news report on environmental pollutants, a specific polyhalogen compound used historically as a solvent was classified under compounds in which the halogen atom is bonded to an $sp^3$ hybridized carbon atom next to a carbon-carbon double bond ($allylic$ carbon). Which of the following compounds fits this structural classification?

   1. (a)2-Bromobut-2-ene
   2. (b)4-Bromopent-2-ene
   3. (c)1-Bromocyclohexene
   4. (d)Bromobenzene
   Show answer and step marks

   1. Correct option: (b) 4-Bromopent-2-ene+1

   Answer: (b)
3. Q3Multiple choice·1 mark
   Which of the following name reactions is specifically utilized for the preparation of aryl chlorides or bromides by treating freshly prepared diazonium salt solution with cuprous chloride or cuprous bromide?

   1. (a)Fittig reaction
   2. (b)Finkelstein reaction
   3. (c)Swarts reaction
   4. (d)Sandmeyer reaction
   Show answer and step marks

   1. Correct option: (d) Sandmeyer reaction+1

   Answer: (d)
4. Q4Multiple choice·1 mark
   Consider the IUPAC nomenclature rules to distinguish between two isomeric halogen derivatives: compound X, $CH_3CH(Cl)CH_2CH_3$, and compound Y, $CH_3CH_2CH_2CH_2Cl$. Which of the following statements correctly distinguishes their IUPAC names and structural types?

   1. (a)Compound X and Compound Y are positional isomers both classified strictly as primary alkyl halides
   2. (b)Compound X is named sec-butyl chloride, while Compound Y is named n-butyl chloride under pure IUPAC guidelines
   3. (c)Compound X is named 2-chlorobutane (secondary alkyl halide), and Compound Y is named 1-chlorobutane (primary alkyl halide)
   4. (d)Compound X is named 3-chlorobutane (tertiary alkyl halide), and Compound Y is named chlorobutane (secondary alkyl halide)
   Show answer and step marks

   1. Correct option: (c) Compound X is named 2-chlorobutane (secondary alkyl halide), and Compound Y is named 1-chlorobutane (primary alkyl halide)+1

   Answer: (c)
5. Q5Multiple choice·1 mark
   At a municipal water treatment facility, technicians investigate methods of preparation of haloalkanes to synthesize specific halogenated tracer compounds. Which of the following reactions represents the Finkelstein reaction used for preparing alkyl iodides?

   1. (a)$\text{R-X} + \text{NaI} \xrightarrow{\text{dry acetone}} \text{R-I} + \text{NaX} \, (\text{X} = \text{Cl, Br})$
   2. (b)$\text{R-OH} + \text{HCl} \xrightarrow{\text{anhydrous } \text{ZnCl}_2} \text{R-Cl} + \text{H}_2\text{O}$
   3. (c)$\text{R-H} + \text{Cl}_2 \xrightarrow{\text{UV light}} \text{R-Cl} + \text{HCl}$
   4. (d)$\text{R-OH} + \text{NaBr} + \text{H}_2\text{SO}_4 \rightarrow \text{R-Br} + \text{NaHSO}_4 + \text{H}_2\text{O}$
   Show answer and step marks

   1. Correct option: (a) $\text{R-X} + \text{NaI} \xrightarrow{\text{dry acetone}} \text{R-I} + \text{NaX} \, (\text{X} = \text{Cl, Br})$+1

   Answer: (a)
6. Q6Multiple choice·1 mark
   Which of the following statements correctly distinguishes between $S_N2$ elimination (dehydrohalogenation) and $S_N1$ elimination pathways in alkyl halides?

   1. (a)Elimination reactions of alkyl halides are strictly endothermic and proceed exclusively via carbanion intermediates.
   2. (b)Dehydrohalogenation typically proceeds via a concerted mechanism with a transition state (E2) or via a carbocation intermediate (E1), whereas substitution reactions compete under basic conditions.
   3. (c)Both $E1$ and $E2$ mechanisms strictly follow second-order kinetics irrespective of the base concentration.
   4. (d)Zaitsev's rule is applicable only to $S_N2$ substitution and never to elimination reactions.
   Show answer and step marks

   1. Correct option: (b) Dehydrohalogenation typically proceeds via a concerted mechanism with a transition state (E2) or via a carbocation intermediate (E1), whereas substitution reactions compete under basic conditions.+1

   Answer: (b)

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