NEET Exam > NEET Notes > Short Notes > Short Notes: Haloalkanes and Haloarenes
Short Notes: Haloalkanes and Haloarenes
1.1 Classification
| Type | Description | Example |
|---|---|---|
| Haloalkanes | Halogen attached to sp³ carbon | CH₃Cl, CH₃CH₂Br |
| Haloarenes | Halogen attached to sp² carbon of aromatic ring | C₆H₅Cl, C₆H₅Br |
| Primary (1°) | Halogen on carbon attached to one carbon | CH₃CH₂Cl |
| Secondary (2°) | Halogen on carbon attached to two carbons | (CH₃)₂CHBr |
| Tertiary (3°) | Halogen on carbon attached to three carbons | (CH₃)₃CCl |
1.2 Nomenclature
- IUPAC: Halo- prefix (fluoro, chloro, bromo, iodo) + parent alkane
- Common names: Alkyl halide format
- Example: CH₃Cl = Chloromethane (IUPAC) or Methyl chloride (Common)
1.3 Preparation Methods
| Method | Reaction | Notes |
|---|---|---|
| From Alcohols | R-OH + HX → R-X + H₂O R-OH + PCl₅ → R-Cl + POCl₃ + HCl R-OH + SOCl₂ → R-Cl + SO₂ + HCl | HX reactivity: HI > HBr > HCl SOCl₂ = Thionyl chloride (best method) |
| Halogenation of Alkanes | R-H + X₂ → R-X + HX (UV light) | Free radical mechanism |
| Addition to Alkenes | CH₂=CH₂ + HBr → CH₃CH₂Br | Follows Markovnikov's rule |
| Haloarenes from Benzene | C₆H₆ + Cl₂ → C₆H₅Cl + HCl (FeCl₃) | Electrophilic substitution |
| Sandmeyer's Reaction | C₆H₅N₂⁺Cl⁻ + CuCl → C₆H₅Cl + N₂ | From diazonium salts |
1.4 Physical Properties
- Boiling Point: Increases with molecular mass and surface area
- Dipole Moment: C-X bond is polar (electronegativity difference)
- Density: Bromo and iodo compounds denser than water
- Solubility: Insoluble in water, soluble in organic solvents
1.5 Chemical Reactions - Nucleophilic Substitution
| Reaction Type | Details |
|---|---|
| SN1 Mechanism | • Two-step mechanism • Rate = k[R-X] • Carbocation intermediate • Racemization occurs • Favored by 3° > 2° > 1° alkyl halides • Polar protic solvents |
| SN2 Mechanism | • One-step mechanism • Rate = k[R-X][Nu⁻] • Transition state (no intermediate) • Inversion of configuration (Walden inversion) • Favored by 1° > 2° > 3° alkyl halides • Polar aprotic solvents |
1.6 Important Reactions
| Reaction | Equation | Product |
|---|---|---|
| With KOH (aq) | R-X + KOH (aq) → R-OH + KX | Alcohol |
| With KOH (alc) | R-CH₂-CH₂-X + KOH (alc) → R-CH=CH₂ | Alkene (Elimination, follows Saytzeff rule) |
| With AgNO₃ (alc) | R-X + AgNO₃ → R-ONO₂ + AgX | Nitrite |
| With KCN | R-X + KCN → R-CN + KX | Nitrile (cyanide) |
| With AgCN | R-X + AgCN → R-NC + AgX | Isocyanide |
| With NH₃ | R-X + NH₃ → R-NH₂ + HX | Amine (Hoffmann ammonolysis) |
| With Na (Wurtz) | 2R-X + 2Na → R-R + 2NaX | Alkane (coupling) |
| With Mg (Grignard) | R-X + Mg → R-MgX (dry ether) | Grignard reagent |
| Reduction | R-X + Zn/HCl → R-H + ZnX₂ | Alkane |
1.7 Haloarenes - Special Properties
- Low reactivity: C-X bond has partial double bond character (resonance)
- Electrophilic substitution: Halogens are ortho-para directing but deactivating
- Nucleophilic substitution: Requires harsh conditions (high temp, pressure)
- Fittig reaction: C₆H₅Cl + C₆H₅Cl + 2Na → C₆H₅-C₆H₅ + 2NaCl
- Wurtz-Fittig: C₆H₅Cl + R-Cl + 2Na → C₆H₅-R
1.8 Polyhalogen Compounds (Important)
| Compound | Formula | Uses/Properties |
|---|---|---|
| Chloroform | CHCl₃ | Anesthetic, solvent; oxidizes to phosgene (COCl₂) - poisonous |
| Iodoform | CHI₃ | Antiseptic; yellow precipitate (iodoform test) |
| CCl₄ | Carbon tetrachloride | Fire extinguisher, solvent |
| Freons (CFCs) | CCl₂F₂ | Refrigerants; deplete ozone layer |
| DDT | (ClC₆H₄)₂CH(CCl₃) | Insecticide; non-biodegradable |
The document Short Notes: Haloalkanes and Haloarenes is a part of the NEET Course Short Notes for NEET.
All you need of NEET at this link: NEET
FAQs on Short Notes: Haloalkanes and Haloarenes
| 1. What are haloalkanes and how are they classified? |  |
Ans. Haloalkanes, also known as alkyl halides, are organic compounds derived from alkanes by the substitution of one or more hydrogen atoms with halogen atoms (F, Cl, Br, I). They are classified based on the number of halogen atoms and the carbon atom's bonding: primary (1°), secondary (2°), and tertiary (3°) haloalkanes, depending on how many carbon atoms are attached to the carbon bearing the halogen.
| 2. What are the physical properties of haloalkanes? | |
Ans. The physical properties of haloalkanes include their state at room temperature (most are liquids), their boiling points which increase with the number of halogen atoms due to increased van der Waals forces, and their solubility. Haloalkanes are generally insoluble in water but soluble in organic solvents due to their non-polar nature.
| 3. Describe the reactivity of haloalkanes. | |
Ans. Haloalkanes are reactive due to the presence of the polar carbon-halogen bond. They undergo nucleophilic substitution reactions, where a nucleophile replaces the halogen atom. The reactivity order of haloalkanes is: RI > RBr > RCl > RF, which indicates that the bond strength decreases as the size of the halogen increases, making the carbon halide more reactive.
| 4. What are haloarenes and how do they differ from haloalkanes? | |
Ans. Haloarenes are aromatic compounds in which one or more hydrogen atoms of an aromatic ring are replaced by halogen atoms. Unlike haloalkanes, haloarenes exhibit resonance stability due to the delocalisation of electrons in the aromatic ring, which affects their reactivity. Haloarenes are less reactive than haloalkanes in nucleophilic substitution reactions due to the stability of the aromatic system.
| 5. What are the common methods for the preparation of haloalkanes? | |
Ans. Haloalkanes can be prepared through several methods, including: 1. Halogenation of alkanes (free radical substitution) by reacting with halogens under UV light. 2. Reaction of alcohols with hydrogen halides to form haloalkanes. 3. Nucleophilic substitution of alkyl groups on haloalkanes. These methods allow for the synthesis of various haloalkanes with different halogens and chain lengths.
About this Document
4.64/5 Rating
Apr 17, 2026 Last updated
Related Exams
Document Description: Short Notes: Haloalkanes and Haloarenes for NEET 2026 is part of Short Notes for NEET preparation. The notes and questions for Short Notes: Haloalkanes and Haloarenes have been prepared according to the NEET exam syllabus. Information about Short Notes: Haloalkanes and Haloarenes covers topics like and Short Notes: Haloalkanes and Haloarenes Example, for NEET 2026 Exam. Find important definitions, questions, notes, meanings, examples, exercises and tests below for Short Notes: Haloalkanes and Haloarenes.
Introduction of Short Notes: Haloalkanes and Haloarenes in English is available as part of our Short Notes for NEET for NEET & Short Notes: Haloalkanes and Haloarenes in Hindi for Short Notes for NEET course. Download more important topics related with notes, lectures and mock test series for NEET Exam by signing up for free. NEET: Short Notes: Haloalkanes and Haloarenes
Description
Short Notes: Haloalkanes & Haloarenes of Short Notes with clear explanations of key concepts & important topics of the chapter, to help you underst& lessons better & revise quickly, & crack the NEET exam.
Information about Short Notes: Haloalkanes and Haloarenes
In this doc you can find the meaning of Short Notes: Haloalkanes and Haloarenes defined & explained in the simplest way possible. Besides explaining types of Short Notes: Haloalkanes and Haloarenes theory, EduRev gives you an ample number of questions to practice Short Notes: Haloalkanes and Haloarenes tests, examples and also practice NEET tests
Related Searches
video lectures, Short Notes: Haloalkanes and Haloarenes, Extra Questions, Sample Paper, practice quizzes, Important questions, MCQs, study material, Free, Short Notes: Haloalkanes and Haloarenes, Viva Questions, Summary, pdf , ppt, mock tests for examination, shortcuts and tricks, Short Notes: Haloalkanes and Haloarenes, Semester Notes, Objective type Questions, Previous Year Questions with Solutions, Exam, past year papers;