Free Free Radical Substitution MCQs with Answers
20 Free Radical Substitution MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Free radical substitution explains how alkanes react with halogens under ultraviolet light or heat through initiation, propagation and termination steps. The mechanism involves homolytic bond fission and radical intermediates, while product formation depends on the relative stability of radicals and differs from ionic substitution.
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20 questions
- A. nucleophilic substitution
- B. electrophilic addition
- C. free radical substitution
- D. elimination
Explanation: Ultraviolet light splits the chlorine molecule homolytically into two radicals, which then abstract hydrogen from methane and set up a…
Correct answer: free radical substitution- A. the reaction of a chlorine radical with methane
- B. the combination of two methyl radicals
- C. the reaction of a methyl radical with chlorine
- D. the homolytic splitting of a chlorine molecule into two chlorine radicals by ultraviolet light
Explanation: Initiation is the step that creates radicals where there were none, and only the chlorine to chlorine bond is weak enough to be broken by…
Correct answer: the homolytic splitting of a chlorine molecule into two chlorine radicals by ultraviolet light- A. Low pressure
- B. Low temperature
- C. High pressure
- D. Heat and UV light
Explanation: Initiation requires the halogen molecule to split homolytically into two radicals, and only ultraviolet light or a high temperature…
Correct answer: Heat and UV light- A. I2>Cl2>Br2>F2
- B. F2>Cl2>I2>Br2
- C. F2>Cl2>Br2>I2
- D. Cl2>F2>Br2>I2
Explanation: The ease of halogenation follows F2 > Cl2 > Br2 > I2 because fluorination is extremely rapid and iodination is generally unfavourable…
Correct answer: F2>Cl2>Br2>I2- A. Benzyl chloride
- B. o - chlorotoluene
- C. p - chlorotoluene
- D. benzoic acid
Explanation: In sunlight, chlorine forms radicals that substitute a hydrogen atom at the benzylic position of toluene, producing benzyl chloride…
Correct answer: Benzyl chloride- A. Benzy1 chloride
- B. Benzal dichloride
- C. O-chlorotoluene
- D. O-chlorotoluene and P-chlorotoluene
Explanation: In sunlight, chlorine forms radicals and preferentially replaces a hydrogen at the benzylic position of toluene, producing benzyl…
Correct answer: Benzy1 chloride- A. CH3*
- B. (CH3)2CH*
- C. (CH3)3C*
- D. C2HS*
Explanation: Attachment of the alkyl group increases the stability of free radicals as alkyl groups are electron donating through the hyperconjugation…
Correct answer: (CH3)3C*- A. Initiation step
- B. Propagation step
- C. Termination step
- D. All same
Explanation: In a free radical substitution reaction of an alkane, the reaction can proceed through several steps involving free radicals (species with…
Correct answer: Termination step- A. Propagation
- B. Free radical substitution
- C. Addition
- D. Elimination
Explanation: The correct answer is 'Free radical substitution.' This mechanism involves the substitution of hydrogen atoms in alkanes with halogen…
Correct answer: Free radical substitution- A. CH3+
- B. (CH3)2CH+
- C. (CH3)3C+
- D. C2H5+
Explanation: Options A and D are incorrect as they are primary free radicals. Option B is incorrect as it's a secondary free radical.
Correct answer: (CH3)3C+- A. C2H4 + Cl2 -> C2H2Cl2 + H2
- B. C2H6 + Cl2 -> C2H5Cl + HCl
- C. C2H4 + Cl2 -> 2CH3Cl
- D. C2H4 + O2 -> 2CH2Cl + 2HCl
Explanation: Ethane reacts with chlorine by free radical halogenation in the presence of In the presence of sunlight, Cl2 breaks down (homolytically)…
Correct answer: C2H6 + Cl2 -> C2H5Cl + HCl- A. Hydrogen free radical
- B. Chlorine free radical
- C. Hydrogen chloride molecule
- D. Both hydrogen and chlorine free radicals
Explanation: To break the covalent bond between two chlorine atoms, photons of ultraviolet rays are required.
Correct answer: Chlorine free radical- A. Cl2
- B. F2
- C. I2
- D. Br2
Explanation: 'Fluorine' (F2) is the most reactive halogen as it has a small size and high charge density.
Correct answer: F2- A. CHCl3
- B. CCl4
- C. CH2Cl2, CH3Cl
- D. All of these
Explanation: It shows a free radical substitution reaction in which UV light (sunlight) is used to substitute the Hs of the CH4.
Correct answer: All of these- A. Heat
- B. Sunlight
- C. Catalyst
- D. Oxygen
Explanation: 'Ultraviolet light' is simply a source of energy and is being used to break bonds.
Correct answer: Sunlight- A. Nitric acid
- B. Oxygen
- C. Halogen
- D. All of these
Explanation: Reason: Alkanes undergo very few reactions. One of these is the reaction with halogens to form halogenoalkanes.
Correct answer: Halogen- A. Cl2
- B. F2
- C. I2
- D. Br2
Explanation: Fluorine (F) is the most reactive halogen and therefore reacts faster with alkanes in substitution reactions.
Correct answer: F2- A. Heat
- B. Sun light
- C. Catalyst
- D. Oxygen
Explanation: Option B is correct since sunlight is simply a source of energy, and is being used to break bonds.
Correct answer: Sun light- A. Nitric acid
- B. Oxygen
- C. Halogen
- D. All of these options are correct
Explanation: When halogens react with alkanes, the reaction is a free radical reaction.
Correct answer: Halogen- A. Cl-
- B. Cl+
- C. Cl2
- D. Cl0
Explanation: A free radical is an atom, molecule or ion that has an unpaired electron.
Correct answer: Cl0Free Radical Substitution MCQs: common questions
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