On Learn Chemistry by Inam Jazbi, I break down organic reactions into clear patterns guided by three major attacking species: electrophiles, nucleophiles, and free radicals. These aren’t just names; they’re the forces that decide how every reaction starts, shifts, and completes. Once you understand how they behave, the entire world of mechanisms begins to feel predictable and almost easy to decode.
Types of Organic Attacking Reagents
The species which attack on a substrate molecule or intermediate and form a product is called as attacking reagent. These are of two types:
1. Electrophilic reagent or electrophiles
2. Nucleophilic reagent or nucleophiles
3. Free radicals
Electrophiles OR
Electrophilic Reagents
1. A chemical reagent which can accept an electron pair in a reaction is called an electrophile. Thus they act as electron pair acceptor during a reaction. They attack on the negative centre of the molecules and love electrons. They are represented by E⁺.
2. The name electrophile means “electron-loving” which indicates that an electrophile always attacks regions of high electron density (negative centers) in the substrate molecule due to deficiency of electrons.
3. They are also called Lewis Acid as they are electron-deficient species and hence have an affinity for electrons.
4. All electrophiles are either positive ions or cations having positive charge (even partial) or neutral electron-deficient molecules (molecule with sextet or septet). Thus all cations are considered to be electrophiles. Free radicals, carbenes & nitrene acts as electrophiles.
Quick recognition
If it feels empty, positive, or electron-poor, it behaves like an electrophile.
Examples
⚡All cations/Positive Ions (Positively charged electrophiles)
⚡Neutral molecules with electron-deficient centers (All Lewis acids)/Neutral Electrophiles
⭐🧠 Exam Boost Summary of Electrophiles (E⁺)
📝 ē-deficient species
📝 ē-loving (having an affinity for ē)
📝 Attacks the point of high electron density (negative center)
📝 Act as Lewis acid as they accept an electron pair (electron pair acceptor).
📝 Forms an extra bond with the nucleophile
📝 Possess an empty orbital to receive the electron pair
📝They undergo electrophilic addition and electrophilic substitution reactions
📝 Mostly acidic
📝 Positively charged species (H⁺, NO₂⁺, CH₃⁺ etc.) or neutral species (SO₃, BF₃ etc.) with electron deficient centre
📝 All carbocations are electrophiles
📝 Free radicals, carbenes & nitrene acts as electrophiles.
📝 Electrophilicity α Electropostive character
nucleophiles or
Nucleophilic Reagents
1. A chemical reagent which can donate an electron pair in a reaction to an electron deficient part to make a new covalent bond is called a nucleophile. They attack on the positive site of the substrate molecule or loves electron. Thus they act as an electron pair donor during a reaction. They are represented by N̈/Nu⁻/ N⁻/N̈u
2. The name nucleophile means “nucleus-loving” which indicates that a nucleophile always attacks regions of low electron density (positive centers) in the substrate molecule due to sufficiency of electrons.
3. They are also called Lewis Base as they are electron-rich species and hence have an affinity for positive nucleus.
4. All nucleophiles are either negative ions or anions having negative charge (even partial) or neutral molecules with p-electrons or unshared or lone electron pair. All anions, unsaturated compounds (alkenes, alkynes, arenas) and compounds having lone pair of electrons are considered to be nucleophile.
Quick recognition
If it has lone pairs, negative charge, or high electron density, it acts as a nucleophile.
Examples
⭐🧠 Exam Boost Summary of Nucleophiles (N̈/Nu⁻/ N⁻/N̈u)
📝 ē-rich species📝 Nucleus-lover (having an affinity for nucleus)
📝 Attacks the point of low electron density
📝 Act as Lewis base (ligand) as they donate an electron pair (electron pair donor).
📝 Able to increases its covalency by one unit.
📝 Possess a loosely held electron pair which can be supplied easily.
📝 They undergo nucleophilic addition and nucleophilic substitution reactions
📝 Mostly basic
📝 Negativley charged species (Cl⁻, OH⁻, CN⁻, NH₂⁻, CH₃⁻ etc.) or neutral species (NH₃, H₂O etc.) with lone pair of electrons or pi bonds (alkenes, alkynes, benzene).
📝 All carboanions are nucleophiles
📝 Formed by heterolytic fission
Difference between Electrophile and Nucleophile
Nucleophile Vs Base
Nucleophilicity and electrophilicity
The extent to which a species can donate a pair of electrons” is called nucleophilicity while the extent to which a species can accept a lone pair of electrons is called “electrophilicity”.
Nucleophilic character
Nucleophilic character α size of molecule α 1/EN α 1/basic character or basicity
Ambident nucleophile
Nucleophiles which have two sites of electron rich centre or in which two or more atoms bear an unshared pair of electrons are called ambident nucleophiles. Resonating structures are also ambident nucleophile.
Amphiphile
Amphiphile are some species switch role depending on the situation acting as both electrophiles or nucleophiles. Molecule containing a multiple bond between carbon and a more electronegative atom can act both as electrophiles or nucleophiles.
Examples
H₂O
NH₃
Alcohols
Carboxylates
For example
Free Radicals
Definition
Neutral but dramatic participants with one unpaired electron.
Key Features
⚡Highly reactive
⚡Formed by homolytic bond cleavage
⚡Attack where radicals can be stabilized
Common Examples
⚡Cl•
⚡Br•
⚡CH₃•
Where they appear
Mostly in halogenation, substitution, and chain reactions under UV light.
⭐🧠 Exam Boost Summary of Free Radical (FR)
📝 Uncharged atom or molecule having unpaired ē📝 Produced as a result of homolysis
📝 Highly reactive
📝 Short-lived
📝 Paramagnetic
📝 Cl•, CH₃• etc.
📝 Reactivity order: tert. FR > sec. FR > primary FR > Methyl FR
🎯 Quick Table for Final Revision
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🔑 Exam Tips
⚡ Carbonyl carbon = electrophilic
⚡Lone pair species = usually nucleophilic
⚡UV light reactions = radical pathway
⚡Lewis acids = electrophiles
⚡Strong bases = strong nucleophiles
💡🌈 How to Instantly Identify Them
✨ Positive or electron-poor = Electrophile
✨ Negative or lone pairs = Nucleophile
✨ Dot (•) = Free Radical
✨ UV light reactions = Radical mechanism
✨ Lewis acids = Electrophiles
✨ Strong bases = Often nucleophiles
🌟🧪 Types of Organic Attacking Reagents – Quiz by Inam Jazbi
1. Which of the following is an electrophile?
🟥 A) Br⁻
🟦 B) H⁺
🟩 C) OH⁻
🟨 D) NH₃
💡 Hint: Electrophiles are electron-seeking species.
2. Nucleophiles are:
🟥 A) Electron donors
🟦 B) Electron acceptors
🟩 C) Neutral radicals
🟨 D) Protons
3. Which of the following is a common free radical?
🟥 A) CH₃•
🟦 B) Cl⁻
🟩 C) H⁺
🟨 D) OH⁻
4. Electrophilic addition reactions occur typically with:
🟥 A) Alkanes
🟦 B) Alkenes
🟩 C) Alkynes
🟨 D) Aromatic compounds
5. Nucleophilic substitution reactions usually involve:
🟥 A) A nucleophile attacking an electron-deficient carbon
🟦 B) A free radical abstracting a hydrogen
🟩 C) Protonation of an alkene
🟨 D) Oxidation of alcohol
6. Which of these is both a nucleophile and a base?
🟥 A) OH⁻
🟦 B) H⁺
🟩 C) Br₂
🟨 D) Cl•
7. Which statement is correct about free radicals?
🟥 A) They have an unpaired electron
🟦 B) They are electron-rich species
🟩 C) They always act as electrophiles
🟨 D) They are stable in all conditions
8. In bromination of alkenes, Br₂ acts as a/an:
🟥 A) Electrophile
🟦 B) Nucleophile
🟩 C) Free radical
🟨 D) Base
9. Which of the following is a nucleophilic reagent?
🟥 A) CN⁻
🟦 B) H⁺
🟩 C) Br•
🟨 D) Cl₂
10. Radical polymerization is initiated by:
🟥 A) Free radicals
🟦 B) Electrophiles
🟩 C) Nucleophiles
🟨 D) Bases
11. Which reagent attacks the electron-rich part of a molecule?
🟥 A) Electrophile
🟦 B) Nucleophile
🟩 C) Free radical
🟨 D) Neutral molecule
12. In organic chemistry, CH₃⁻ is a/an:
🟥 A) Nucleophile
🟦 B) Electrophile
🟩 C) Free radical
🟨 D) Acid
13. Which of these is typical in halogenation under light?
🟥 A) Free radical mechanism
🟦 B) Nucleophilic substitution
🟩 C) Electrophilic addition
🟨 D) Acid-base reaction
14. Electrophiles are generally:
🟥 A) Electron-deficient
🟦 B) Electron-rich
🟩 C) Neutral radicals
🟨 D) Bases
15. OH⁻ attacking CH₃Br is an example of:
🟥 A) Nucleophilic substitution
🟦 B) Electrophilic addition
🟩 C) Radical halogenation
🟨 D) Elimination reaction
✅ Answers
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1. 🟦 B – H⁺
2. 🟥 A – Electron donors
3. 🟥 A – CH₃•
4. 🟦 B – Alkenes
5. 🟥 A – Nucleophile attacking electron-deficient carbon
6. 🟥 A – OH⁻
7. 🟥 A – Unpaired electron
8. 🟥 A – Electrophile
9. 🟥 A – CN⁻
10. 🟥 A – Free radicals
11. 🟥 A – Electrophile
12. 🟥 A – Nucleophile
13. 🟥 A – Free radical mechanism
14. 🟥 A – Electron-deficient
15. 🟥 A – Nucleophilic substitution
