A covalent bond can get cleaved either by : (i) heterolytic cleavage, or by (ii) homolytic cleavage.
-- NCERT Class 11 Chemistry, Ch. 8, p. 271Homolytic Heterolytic Fission
8 MCQs9-step worked example
Source: NCERT Organic Chemistry — Some Basic PrinciplesOfficial key: NTA-verifiedLast updated: 8 Oct 2026
Try this first
In heterolytic cleavage of a covalent bond, what happens to the shared pair of electrons?
- A.It is shared equally, one electron going to each fragment
- B.It remains with one of the fragments
- C.It is lost from both fragments
- D.It becomes two unpaired electrons on the same atom
Tap to see the answer
Answer: B. In heterolytic cleavage the bond breaks so that the shared pair of electrons remains with one of the fragments (NCERT Class 11 Chemistry, Chapter 8, page 271).
A is wrong: A is wrong because one electron going to each fragment describes homolytic cleavage (NCERT Class 11 Chemistry, Chapter 8, page 272).
C is wrong: C is wrong because the electrons are not lost; the pair goes entirely to one fragment, which gives that fragment a negative charge (NCERT Class 11 Chemistry, Chapter 8, page 271).
D is wrong: D is wrong because heterolysis moves an electron pair, not single electrons, and gives ions rather than radicals (trap: mixing up ions and radicals).
Homolytic Heterolytic Fission, explained for NEET
When the C–Br bond in bromomethane breaks, where do the two bonding electrons go? The answer decides whether you get a pair of ions or a pair of neutral fragments, and so which kind of reaction follows.
A covalent bond can get cleaved either by heterolytic cleavage or by homolytic cleavage (NCERT Class 11 Chemistry, Chapter 8, page 271).
In heterolytic cleavage, the bond breaks in such a fashion that the shared pair of electrons remains with one of the fragments. After heterolysis, one atom has a sextet electronic structure and a positive charge, and the other has a valence octet with at least one lone pair and a negative charge; heterolytic cleavage of bromomethane gives CH₃⁺ and Br⁻ (NCERT Class 11 Chemistry, Chapter 8, page 271).
A species having a carbon atom with a sextet of electrons and a positive charge is called a carbocation (NCERT Class 11 Chemistry, Chapter 8, page 271). The same cleavage can also leave the pair on carbon, which gives a species with a negative charge on carbon, called a carbanion (NCERT Class 11 Chemistry, Chapter 8, page 272). Reactions that proceed through heterolytic cleavage are called ionic, heteropolar or just polar reactions (NCERT Class 11 Chemistry, Chapter 8, page 272).
In homolytic cleavage, one of the electrons of the shared pair goes with each of the bonded atoms, so the movement of a single electron takes place instead of an electron pair (NCERT Class 11 Chemistry, Chapter 8, page 272). Such cleavage gives neutral species that contain an unpaired electron, called free radicals (NCERT Class 11 Chemistry, Chapter 8, page 272). Reactions that proceed by homolytic fission are called free radical, homopolar or nonpolar reactions (NCERT Class 11 Chemistry, Chapter 8, page 272).
Watch out: the word "hetero" means the pair goes to one side and ions form; "homo" means the pair is shared out one electron each and radicals form.
How do you solve a Homolytic Heterolytic Fission question? A worked example
- 1
Given
The bond in H₃C–Br breaks. Case 1: both electrons of the bond go to bromine. Case 2: one electron goes to each atom.
- 2
Required
The species formed in each case, and the name of each type of cleavage and of the reactions that follow it.
- 3
Concept
If the shared pair remains with one fragment, the cleavage is heterolytic (NCERT Class 11 Chemistry, Chapter 8, page 271). If one electron goes with each atom, the cleavage is homolytic and gives free radicals (NCERT Class 11 Chemistry, Chapter 8, page 272).
- 4
Formula
No formula is needed; the counting rule is: heterolysis, pair to one atom; homolysis, one electron to each.
- 5
Substitution
Case 1: the pair goes to Br, so Br holds the pair and the carbon keeps only three C–H bonds. Case 2: each of C and Br takes one of the two bonding electrons.
- 6
Calculation
Case 1: Br ends with an octet, a lone pair and a negative charge; carbon has 3 × 2 = 6 electrons, a sextet, and a positive charge. Case 2: each fragment is neutral with one unpaired electron.
- 7
Final answer
Case 1 is heterolytic cleavage and gives CH₃⁺ and Br⁻, an ionic (polar) reaction path (NCERT Class 11 Chemistry, Chapter 8, pages 271 and 272). Case 2 is homolytic cleavage and gives the free radicals CH₃• and Br•, a free radical (nonpolar) reaction path (NCERT Class 11 Chemistry, Chapter 8, page 272).
- 8
Common trap
Writing charges on the products of homolysis. Free radicals are neutral; the unpaired electron, not a charge, is what marks them.
- 9
Similar NEET-style question
A bond A–B breaks so that both electrons go to B. Name the cleavage, and say whether B ends up with a positive or a negative charge. (Answer: heterolytic cleavage; B holds the extra pair, so B carries a negative charge and A carries a positive charge.)
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Can you answer these Homolytic Heterolytic Fission MCQs?
Select an option to see the explanation. Wrong answers show why your choice was tempting — and name the exact trap it exploits.
MCQ 1Easy RecallPractice
In heterolytic cleavage of a covalent bond, what happens to the shared pair of electrons?
Show answer and why every option is right or wrong
Answer: B. In heterolytic cleavage the bond breaks so that the shared pair of electrons remains with one of the fragments (NCERT Class 11 Chemistry, Chapter 8, page 271).
Why A is wrong: A is wrong because one electron going to each fragment describes homolytic cleavage (NCERT Class 11 Chemistry, Chapter 8, page 272).
Why C is wrong: C is wrong because the electrons are not lost; the pair goes entirely to one fragment, which gives that fragment a negative charge (NCERT Class 11 Chemistry, Chapter 8, page 271).
Why D is wrong: D is wrong because heterolysis moves an electron pair, not single electrons, and gives ions rather than radicals (trap: mixing up ions and radicals).
MCQ 2Easy RecallPractice
Homolytic cleavage of a covalent bond gives
Show answer and why every option is right or wrong
Answer: D. Homolytic cleavage forms neutral species (atoms or groups) that contain an unpaired electron; these are called free radicals (NCERT Class 11 Chemistry, Chapter 8, page 272).
Why A is wrong: A is wrong because a carbocation and a carbanion are the charged species of heterolytic cleavage (NCERT Class 11 Chemistry, Chapter 8, pages 271 and 272).
Why B is wrong: B is wrong because homolysis gives neutral fragments, not anions (NCERT Class 11 Chemistry, Chapter 8, page 272).
Why C is wrong: C is wrong because no electron pair is removed from a fragment in homolysis, so no cation forms (NCERT Class 11 Chemistry, Chapter 8, page 272).
MCQ 3Easy RecallPractice
What is a carbocation, according to NCERT?
Show answer and why every option is right or wrong
Answer: C. NCERT calls a species with a carbon atom possessing a sextet of electrons and a positive charge a carbocation, earlier called a carbonium ion (NCERT Class 11 Chemistry, Chapter 8, page 271).
Why A is wrong: A is wrong because a neutral carbon species with an unpaired electron is a free radical (NCERT Class 11 Chemistry, Chapter 8, page 272).
Why B is wrong: B is wrong because a carbon atom with a negative charge is a carbanion (NCERT Class 11 Chemistry, Chapter 8, page 272).
Why D is wrong: D is wrong because a carbon with an octet and a lone pair is the carbanion side of the heterolysis, with a negative charge (trap: swapping the carbocation and carbanion descriptions).
MCQ 4Direct ApplicationPractice
Heterolytic cleavage of the C–Br bond in bromomethane (H₃C–Br) gives which pair of species?
Show answer and why every option is right or wrong
Answer: C. The shared pair stays with the bromine, which then has an octet with a lone pair and a negative charge; carbon is left with a sextet and a positive charge, so CH₃⁺ and Br⁻ form (NCERT Class 11 Chemistry, Chapter 8, page 271).
Why A is wrong: A is wrong because CH₃• and Br• are the free radicals that homolytic cleavage would give (NCERT Class 11 Chemistry, Chapter 8, page 272).
Why B is wrong: B is wrong because it gives the pair to carbon; NCERT shows the pair going with bromine, which gives CH₃⁺ and Br⁻ (NCERT Class 11 Chemistry, Chapter 8, page 271).
Why D is wrong: D is wrong because CH₂ and HBr would need a hydrogen to move, which is not cleavage of the C–Br bond alone (trap: confusing bond fission with elimination).
MCQ 5Direct ApplicationPractice
Reactions that proceed by homolytic fission are also called
Show answer and why every option is right or wrong
Answer: D. Organic reactions that proceed by homolytic fission are called free radical, homopolar or nonpolar reactions (NCERT Class 11 Chemistry, Chapter 8, page 272).
Why A is wrong: A is wrong because ionic, heteropolar or polar reactions are the ones that proceed through heterolytic cleavage (NCERT Class 11 Chemistry, Chapter 8, page 272).
Why B is wrong: B is wrong because homolysis does not produce an electron-poor ion; it produces free radicals, so the label electrophilic does not describe it (NCERT Class 11 Chemistry, Chapter 8, page 272).
Why C is wrong: C is wrong because homolysis does not give a species carrying an electron pair; it gives radicals (NCERT Class 11 Chemistry, Chapter 8, page 272).
MCQ 6Direct ApplicationPractice
Which statement correctly contrasts the electron movement in the two kinds of bond fission?
Show answer and why every option is right or wrong
Answer: B. In heterolysis the shared pair goes to one fragment (NCERT Class 11 Chemistry, Chapter 8, page 271). In homolysis a single electron goes with each atom, so the movement of a single electron takes place instead of an electron pair (NCERT Class 11 Chemistry, Chapter 8, page 272).
Why A is wrong: A is wrong because only heterolysis sends the pair to one atom; homolysis splits the pair one electron each (NCERT Class 11 Chemistry, Chapter 8, page 272).
Why C is wrong: C is wrong because it swaps the two definitions (trap: reversing heterolytic and homolytic).
Why D is wrong: D is wrong because both fissions break a shared electron pair; they differ in where the electrons end up (NCERT Class 11 Chemistry, Chapter 8, pages 271 and 272).
MCQ 7CalculationPractice
A group Z leaves the carbon of H₃C–Z without taking the electron pair, so the pair stays on carbon. Which species forms on carbon, and which class of reaction does this cleavage belong to?
Show answer and why every option is right or wrong
Answer: B. If the pair stays on carbon, carbon carries a negative charge and the species is a carbanion (NCERT Class 11 Chemistry, Chapter 8, page 272). Cleavage that sends the pair to one fragment is heterolytic, and reactions through heterolytic cleavage are ionic or polar reactions (NCERT Class 11 Chemistry, Chapter 8, page 272).
Why A is wrong: A is wrong on both counts: a carbocation has lost the pair, and a free radical reaction needs homolytic fission (NCERT Class 11 Chemistry, Chapter 8, page 272).
Why C is wrong: C is wrong because the carbanion is right but the class is not; the pair moves as a unit, so the cleavage is heterolytic and the reaction is ionic (NCERT Class 11 Chemistry, Chapter 8, page 272).
Why D is wrong: D is wrong because the class is right but the species is not; a carbocation forms when carbon loses the pair, not when it keeps it (trap: swapping carbocation and carbanion).
MCQ 8CalculationPractice
In the methyl cation CH₃⁺, carbon forms three C–H bonds and has no other electrons around it. How many electrons are around the carbon atom, and does that match NCERT's description of a carbocation?
Show answer and why every option is right or wrong
Answer: C. Three C–H bonds hold 3 × 2 = 6 electrons around carbon, a sextet, which matches NCERT's carbocation: a carbon atom possessing a sextet of electrons and a positive charge (NCERT Class 11 Chemistry, Chapter 8, page 271).
Why A is wrong: A is wrong because 8 electrons would need a lone pair on carbon, which is the carbanion case (NCERT Class 11 Chemistry, Chapter 8, page 272).
Why B is wrong: B is wrong because 7 electrons would not fit three bonds and no other electrons; an unpaired electron belongs to a free radical (NCERT Class 11 Chemistry, Chapter 8, page 272).
Why D is wrong: D is wrong because the count of 6 is right but a carbocation is defined by a sextet, not an octet (NCERT Class 11 Chemistry, Chapter 8, page 271).
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What to remember before solving Homolytic Heterolytic Fission questions
8 NCERT lines
In heterolytic cleavage, the bond breaks in such a fashion that the shared pair of electrons remains with one of the fragments. After heterolysis, one atom has a sextet electronic structure and a positive charge and the other, a valence octet with at least one lone pair and a negative charge.
-- NCERT Class 11 Chemistry, Ch. 8, p. 271A species having a carbon atom possessing sextext of electrons and a positive charge is called a carbocation (earlier called carbonium ion).
-- NCERT Class 11 Chemistry, Ch. 8, p. 271Such a carbon species carrying a negative charge on carbon atom is called carbanion.
-- NCERT Class 11 Chemistry, Ch. 8, p. 272The organic reactions which proceed through heterolytic bond cleavage are called ionic or heteropolar or just polar reactions.
-- NCERT Class 11 Chemistry, Ch. 8, p. 272Definition
Homolytic cleavage: one electron of the shared pair goes to each atom; a single electron moves
In homolytic cleavage, one of the electrons of the shared pair in a covalent bond goes with each of the bonded atoms. Thus, in homolytic cleavage, the movement of a single electron takes place instead of an electron pair.
-- NCERT Class 11 Chemistry, Ch. 8, p. 272Such cleavage results in the formation of neutral species (atom or group) which contains an unpaired electron. These species are called free radicals.
-- NCERT Class 11 Chemistry, Ch. 8, p. 272Organic reactions, which proceed by homolytic fission are called free radical or homopolar or nonpolar reactions.
-- NCERT Class 11 Chemistry, Ch. 8, p. 272Homolytic Heterolytic Fission: NEET previous year questions (PYQs) with answers
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Sources
NCERT refs: Class 11 Chemistry Chapter 8, p.271 | Class 11 Chemistry Chapter 8, p.272
Page numbers are the ones printed in the current NCERT textbook (2023 rationalised edition), unless marked pre-2023. The books are free at ncert.nic.in.
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