ChemistryChapter 15: Organic Chemistry
Bond Fission and Reagent Types
Homolytic fission: each atom takes one electron, radicals (odd e-) named.
Learning objectives
- Explain bond fission and reagent types in simple chemical language.
- Connect 1. fission with 2. nu and e+ using equations, observations, or trends where needed.
- Answer a short Federal Board question with the correct terms and a clear reason.
Definition
Homolytic fission: each atom takes one electron, radicals (odd e-) named. Heterolytic: both electrons stay with one atom, ions (carbocation / carbanion named). Reagents: electrophile wants electrons (Br-d+ in Br2/alkene school). Nucleophile has a pair to give (OH-, NH3, CN- named as school examples). Free-radical named in methane + Cl2 (light) as a type, not a chain-weapon story. Meaning: the arrow in a mechanism follows the pair (school curly arrows if asked). Homolytic: one e each — radicals; heterolytic: both e to one atom — ion pair. Convert between formula types before naming; longest chain and lowest locants decide IUPAC marks.
Important terms
- BOND FISSION AND REAGENT TYPES
- Homolytic fission: each atom takes one electron, radicals (odd e-) named.
- 1. FISSION
- UV on Cl2: radicals (named initiation).
- 2. Nu AND E+
- OH- attacks carbon of C-Br (later SN2 idea).
Relationship
- homo = radicals
- hetero = ions
Overview
Split, then who attacks:
Fission
UV on Cl2: radicals (named initiation). Heterolytic in SN1 (later) makes a carbocation. Do not write harmful radical-chain processes. Electrophile seeks e- pair; nucleophile donates e- pair — labels for organic mechanisms.
Examples Cl-Cl light · C-Cl in SN1 named · Ions in polar solvents
Nu AND E+
OH- attacks carbon of C-Br (later SN2 idea). Alkene C=C attacks Br-Br (electrophilic addition). Acid H+ is an electrophile. Curved arrows show electron movement in mechanism sketches.
Examples OH- nucleophile · Br2 electrophile with alkenes · NH3 nucleophile named
WHAT — BOND FISSION AND REAGENT TYPES
Homolytic fission: each atom takes one electron, radicals (odd e-) named. Heterolytic: both electrons stay with one atom, ions (carbocation / carbanion named). Reagents: electrophile wants electrons (Br-d+ in Br2/alkene school). Nucleophile has a pair to give (OH-, NH3, CN- named as school examples). Free-radical named in methane + Cl2 (light) as a type, not a chain-weapon story. Meaning: the arrow in a mechanism follows the pair (school curly arrows if asked). Homolytic: one e each — radicals; heterolytic: both e to one atom — ion pair. Convert between formula types before naming; longest chain and lowest locants decide IUPAC marks.
WHY — Why this topic matters
BOND FISSION AND REAGENT TYPES is an independent FBISE learning unit because students must use its definitions, conditions, equations, or trends separately in explanations and calculations.
HOW — How it works
FISSION: UV on Cl2: radicals (named initiation). Heterolytic in SN1 (later) makes a carbocation. Do not write harmful radical-chain processes. Electrophile seeks e- pair; nucleophile donates e- pair — labels for organic mechanisms. Examples: Cl-Cl light; C-Cl in SN1 named; Ions in polar solvents. Nu AND E+: OH- attacks carbon of C-Br (later SN2 idea). Alkene C=C attacks Br-Br (electrophilic addition). Acid H+ is an electrophile. Curved arrows show electron movement in mechanism sketches. Examples: OH- nucleophile; Br2 electrophile with alkenes; NH3 nucleophile named. Exam pair: nucleophile: electron-pair donor (OH-) electrophile: electron-pair acceptor (H+, Br2 with alkenes) homolytic fission makes radicals
In simple words
School types. No radical-weapon or illicit mechanism sheets.
Key points
- homo = radicals
- hetero = ions
- Nu has a pair, E+ wants a pair
- one e- each vs pair stays
- pair to empty / d+
Exam preparation
Exam Focus
Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.Bond Fission and Reagent Types
Sticky Notes · Quick Revision
Core Idea
- Homolytic fission: each atom takes one electron, radicals (odd e-) named. Heterolytic: both electrons stay with one atom, ions (carbocation / carbanion named). Reagents: electrophile wants electrons (Br-d+ in Br2/alkene school). Nucleophile has a pair to give (OH-, NH3, CN- named as school examples). Free-radical named in methane + Cl2 (light) as a type, not a chain-weapon story. Meaning: the arrow in a mechanism follows the pair (school curly arrows if asked). Homolytic: one e each — radicals; heterolytic: both e to one atom — ion pair. Convert between formula types before naming; longest chain and lowest locants decide IUPAC marks.
1. FISSION
- UV on Cl2: radicals (named initiation). Heterolytic in SN1 (later) makes a carbocation. Do not write harmful radical-chain processes. Electrophile seeks e- pair; nucleophile donates e- pair — labels for organic mechanisms.
- Cl-Cl light
- C-Cl in SN1 named
- Ions in polar solvents
2. Nu AND E+
- OH- attacks carbon of C-Br (later SN2 idea). Alkene C=C attacks Br-Br (electrophilic addition). Acid H+ is an electrophile. Curved arrows show electron movement in mechanism sketches.
- OH- nucleophile
- Br2 electrophile with alkenes
- NH3 nucleophile named
Exam Example
- Exam pair:
- nucleophile: electron-pair donor (OH-)
- electrophile: electron-pair acceptor (H+, Br2 with alkenes)
- homolytic fission makes radicals
Common Misconceptions
- Do not confuse 1. FISSION with 2. Nu AND E+; state the difference before giving an example.
- Writing only “homo = radicals” is not enough. Explain what it means in a complete sentence.
FBISE Exam Check
- Explain bond fission and reagent types, compare its two main parts, and include the correct chemical evidence.
- School types. No radical-weapon or illicit mechanism sheets.
60-second revision
- Homolytic fission: each atom takes one electron, radicals (odd e-) named.
- 1. FISSION: UV on Cl2: radicals (named initiation).
- 2. Nu AND E+: OH- attacks carbon of C-Br (later SN2 idea).
- Exam reminder: Exam pair: nucleophile: electron-pair donor (OH-) electrophile: electron-pair acceptor (H+, Br2 with alkenes) homolytic fission makes radicals
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