Haloalkanes and Haloarenes

35 solved questions from Class 12 Chemistry, each with the full working. Tap any question to see the step-by-step solution.

• 1 What is the primary chemical reaction or bonding mechanism highlighted in 'Haloalkanes and Haloarenes' (Class 12)? medium MCQ Reaction Mechanism & Bonding
• 2 What factor affects the rate or equilibrium constant of reactions in 'Haloalkanes and Haloarenes'? medium MCQ Chemical Kinetics & Factors
• 3 Which functional group or IUPAC nomenclature rule applies to compounds in 'Haloalkanes and Haloarenes'? medium MCQ IUPAC Nomenclature & Structure
• 4 What is the major product obtained in the characteristic reaction of 'Haloalkanes and Haloarenes'? medium MCQ Reaction Products & Selectivity
• 5 Explain why nucleophilic substitution of chlorobenzene with NaNH₂ proceeds via the benzyne mechanism rather than a direct SNAr pathway, and outline the steps of this mechanism. hard 5 marks Benzyne mechanism in nucleophilic aromatic substitution
• 6 At 298 K, the standard Gibbs free energy change (ΔG°) for the nucleophilic aromatic substitution of chlorobenzene with sodium amide (NaNH₂) in liquid ammonia is +55 kJ·mol⁻¹. Calculate the equilibrium constant K for this reaction. hard 4 marks Thermodynamic calculation of equilibrium constant
• 7 The hydrolysis of tert-butyl chloride in aqueous solution follows which rate law? Choose the correct option. medium MCQ 3 marks Rate law for SN1 reaction
• 8 1-Bromobutane is treated with excess sodium iodide in dry acetone. Write the major organic product formed and explain the reason for its formation. easy 2 marks SN2 substitution (Finkelstein reaction)
• 9 The nucleophilic aromatic substitution of chlorobenzene with sodium amide in liquid ammonia can proceed by two pathways: direct addition–elimination (SNAr) with rate constant k_1=1.2×10^-6 s^-1 and the benzyne mechanism with rate constant k_2=3.6×10^-5 s^-1. Calculate the ratio k_2/k_1 and state which mechanism dominates. medium 2 marks Rate comparison of SNAr vs benzyne mechanisms
• 10 When 1‑chloropropane (CH_3CH_2CH_2Cl) is refluxed with excess aqueous NaOH, the major product is: medium MCQ 3 marks SN2 substitution of primary haloalkanes
• 11 In a Finkelstein reaction, 1‑bromobutane (C_4H_9Br) is treated with excess sodium iodide in dry acetone at 298 K. The standard Gibbs free energy change for the reaction C_4H_9Br + NaI → C_4H_9I + NaBr is +5.8 kJ mol^-1. (a) Calculate the equilibrium constant K at this temperature. (b) Explain why the reaction still gives a quantitative yield of C_4H_9I despite K<1. hard 5 marks Equilibrium shift in Finkelstein reaction
• 12 The aqueous hydrolysis of tert-butyl bromide ((CH_3)_3CBr) at 30°C follows first‑order kinetics with a half‑life of 2.5×10^3 s. Calculate the rate constant k in s^-1. easy 2 marks First-order kinetics of SN1 hydrolysis
• 13 3‑Chloro‑4‑methylbenzene is reacted with sodium amide (NaNH_2) in liquid ammonia. (a) Does the substitution proceed via the direct SNAr mechanism or via the benzyne mechanism? (b) What is the major organic product formed? (c) Outline the steps of the favored mechanism. hard 5 marks Benzyne mechanism in aromatic substitution
• 14 During the hydrolysis of 1‑iodopropane (CH_3CH_2CH_2I) with excess aqueous NaOH, which rate law correctly describes the reaction? easy MCQ 2 marks Second‑order rate law for SN2
• 15 1‑Chloro‑2‑methylpropane is refluxed with excess aqueous NaOH. Name the major organic product and briefly explain the mechanism. medium 3 marks SN2 substitution of primary alkyl halides
• 16 The aqueous Finkelstein reaction C_4H_9Br + NaI → C_4H_9I + NaBr has a standard Gibbs free energy change of Δ G° = +4.0 kJ,mol^-1 at 298 K. Calculate the equilibrium constant K at this temperature. medium 3 marks Equilibrium constant from ΔG°
• 17 2‑Iodo‑3‑methylpentane is refluxed with excess aqueous NaOH. Name the major organic product and briefly explain the reaction mechanism. medium 3 marks S_N1 hydrolysis of tertiary haloalkane
• 18 1‑Bromobutane is treated with excess sodium amide (NaNH_2) in liquid ammonia. What is the major organic product obtained? easy MCQ 2 marks SN2 substitution of primary alkyl halide
• 19 When 4‑chloro‑3‑methylbromobenzene (C6H4ClBrCH3) is treated with excess sodium amide (NaNH2) in liquid ammonia, which mechanism predominates? Outline the steps of the favoured mechanism and explain why it is preferred over the direct SNAr pathway. hard 5 marks Benzyne mechanism in haloarene substitution
• 20 The hydrolysis of tert‑butyl chloride ((CH3)3CCl) in excess aqueous NaOH at 30 °C follows first‑order kinetics with a half‑life of 2.5×10³ s. Calculate the rate constant k in s⁻¹. medium 2 marks First‑order rate law and half‑life
• 21 In a Finkelstein reaction, 1‑iodobutane (CH3CH2CH2CH2I) is treated with excess NaBr in dry acetone at 298 K. The standard Gibbs free energy change for the reaction is ΔG° = +5.2 kJ mol⁻¹. What is the equilibrium constant K for this reaction at 298 K? medium MCQ 4 marks Calculating equilibrium constants from Gibbs free energy
• 22 2‑Bromopropane is refluxed with excess aqueous NaOH. Identify the major organic product and briefly explain the reaction mechanism. easy 2 marks SN1 substitution of a secondary alkyl halide
• 23 3‑Chloropyridine is treated with excess NaNH₂ in liquid ammonia at 298 K. Which mechanism dominates the substitution and what is the major organic product? Briefly outline the steps of the favoured mechanism. hard 4 marks SNAr mechanism for heteroaromatic substitution
• 24 1‑Chlorobutane is reacted with excess aqueous NaOH. Which compound is obtained as the major product? easy MCQ 2 marks SN2 substitution of primary haloalkanes
• 25 In a Finkelstein reaction, 2‑bromobutane (C₄H₉Br) is treated with excess NaI in dry acetone at 298 K. The standard Gibbs free energy change for the reaction is ΔG° = –3.0 kJ mol⁻¹. Calculate the equilibrium constant K for this reaction at 298 K. medium 4 marks Equilibrium constant from ΔG°
• 26 The hydrolysis of tert‑butyl chloride ((CH₃)₃CCl) in excess aqueous NaOH at 30 °C follows first‑order kinetics with a half‑life of 1.0×10³ s. (a) Calculate the rate constant k in s⁻¹. (b) If the initial concentration of tert‑butyl chloride is 0.50 M, what is its concentration after 5.0×10³ s? hard 5 marks First‑order kinetics and concentration decay
• 27 In a Finkelstein reaction, 1‑bromo‑2‑methylpropane (CH_3CH(CH_3)CH_2Br) is treated with excess NaI in dry acetone at 298 K. The standard Gibbs free energy change for the reaction is Δ G°= -2.5 kJ mol^-1. Calculate the equilibrium constant K at this temperature. medium 2 marks ΔG°–K relationship for Finkelstein reaction
• 28 The first‑order hydrolysis of allyl bromide (CH_2=CHCH_2Br) in 0.20 M NaOH at 25 °C has a half‑life of 4.2×10^2 s. (a) Calculate the rate constant k in s^-1. (b) If the initial concentration of allyl bromide is 0.15 M, find its concentration after 1.2×10^3 s. medium 3 marks First‑order kinetics and half‑life
• 29 1‑Chloro‑2,4‑dinitrobenzene (ClC_6H_3(NO_2)_2) is reacted with excess NaNH_2 in liquid ammonia at 298 K. (a) State which nucleophilic aromatic substitution pathway (direct addition‑elimination or benzyne) is favoured and justify. (b) Write the structure of the major organic product. (c) Outline the complete mechanism leading to this product, indicating the role of the strongly basic medium. hard 5 marks Benzyne mechanism in nucleophilic aromatic substitution
• 30 1‑Chloropropane (CH_3CH_2CH_2Cl) is refluxed with excess aqueous NaOH. Which compound is obtained as the major product? easy MCQ 1 mark SN2 substitution of primary haloalkane
• 31 1‑Chloropentane (CH_3CH_2CH_2CH_2CH_2Cl) reacts with excess NaI in dry acetone at 298 K. The standard Gibbs free energy change for the reaction C_5H_11Cl + NaI → C_5H_11I + NaCl is Δ G°= -4.2 kJ mol^-1. Calculate the equilibrium constant K at this temperature. medium 2 marks Thermodynamics of Finkelstein reaction
• 32 During the aqueous hydrolysis of 2‑bromo‑2‑methylpropane ((CH_3)_3CBr) with excess NaOH, which of the following rate laws correctly describes the reaction? hard MCQ 2 marks Rate law for SN1 hydrolysis of tertiary haloalkane
• 33 1‑Bromoisobutane (tert‑butyl bromide, (CH_3)_3CBr) is refluxed with excess aqueous NaOH. Write the major organic product formed and explain the type of mechanism involved. easy 1 mark SN1 hydrolysis of tertiary haloalkane
• 34 p‑Chloronitrobenzene (ClC_6H_4NO_2, chlorine para to the nitro group) is treated with excess NaNH₂ in liquid ammonia at 298 K. hard 4 marks Benzyne mechanism in nucleophilic aromatic substitution
• 35 In a Finkelstein reaction, 1‑chloropropane is converted to 1‑iodopropane by excess NaI in dry acetone at 298 K. The standard Gibbs free energy change for the reaction is ΔG° = –3.4 kJ mol⁻¹. Calculate the equilibrium constant K at this temperature. medium 3 marks Equilibrium constant from Gibbs free energy