# Haloalkanes and Haloarenes, Class 12 Chemistry | SwaVid Haloalkanes and Haloarenes, NCERT Class 12 Chemistry: notes with key ideas, formulas, common mistakes and 3 quick checks with worked answers. Canonical: https://www.swavid.com/cbse/class-12/chemistry/chapter/haloalkanes-and-haloarenes Source: https://www.swavid.com/cbse/class-12/chemistry/chapter/haloalkanes-and-haloarenes # Haloalkanes and Haloarenes ## Formulas and definitions ## Key ideas ## Common mistakes ## Quick checks ## Keep going ## Questions parents ask ## Class 12 Chemistry on SwaVid ### Classification and nature of carbon-halogen bond ### Methods of preparation ### Nucleophilic substitution mechanisms ### Elimination reactions ### Reactivity of haloarenes ### Reactions with metals ### Next chapter ### Related chapter ### Related chapter ### All chapters SwaVid › CBSE › Class 12 › Chemistry › Haloalkanes and Haloarenes Notes written by SwaVid from the NCERT textbook. Class 12 Chemistry, Unit 6. Key ideas, formulas and common mistakes. CBSE prints 6 marks for Unit 6, not for this chapter alone. Short answer. This chapter covers the classification, preparation, properties, and reaction mechanisms of halogen derivatives of aliphatic and aromatic hydrocarbons. It explains nucleophilic substitution, elimination, organometallic compounds, and the relative inertness of haloarenes. Source: NCERT Chemistry Part II (Reprint 2026-27) , Unit 6, Haloalkanes and Haloarenes Haloalkanes contain halogen attached to sp³ hybridised carbon, while haloarenes contain halogen attached to sp² hybridised aromatic carbon. The carbon-halogen bond is polar due to the higher electronegativity of halogen atoms. Haloalkanes are prepared from alcohols using halogen acids, phosphorus halides, or thionyl chloride. They are also prepared from hydrocarbons by free radical halogenation, electrophilic addition to alkenes, and halogen exchange reactions like Finkelstein and Swarts reactions. Substitution nucleophilic bimolecular (SN2) occurs in a single step with complete inversion of configuration, favoured by primary halides. Substitution nucleophilic unimolecular (SN1) proceeds through a carbocation intermediate in two steps, leading to racemisation, and is favoured by tertiary halides. Haloalkanes with beta-hydrogen atoms undergo dehydrohalogenation on heating with alcoholic potassium hydroxide. According to Zaitsev rule, the preferred alkene is the one with the greater number of alkyl groups attached to the doubly bonded carbon atoms. Haloarenes are extremely less reactive towards nucleophilic substitution due to resonance stabilization, differences in hybridisation of the carbon atom, instability of the phenyl cation, and electron repulsion. Electron-withdrawing groups at ortho and para positions increase their reactivity towards nucleophilic substitution. Alkyl halides react with magnesium in dry ether to form Grignard reagents (RMgX). Aryl halides undergo the Wurtz-Fittig and Fittig reactions with sodium in dry ether to form alkylarenes and diphenyl, respectively. Try each question first. Then tap it to see the answer. S N1 reaction rate depends on the stability of the intermediate carbocation. 2-Chloro-2-methylpropane forms a tertiary carbocation, (CH₃)₃C⁺, which is highly stable. 1-Chlorobutane forms a primary carbocation, CH₃CH₂CH₂CH₂⁺, which is least stable. 2-chloro-2-methylpropane The reaction is a beta-elimination (dehydrohalogenation). Beta-hydrogens are present on C1 and C3. Elimination from C1 gives pent-1-ene, while elimination from C3 gives pent-2-ene. By Zaitsev rule, the more substituted alkene is the major product. pent-2-ene This reaction is the Wurtz-Fittig reaction. Equation: C₆H₅Br + 2Na + CH₃Br → C₆H₅-CH₃ + 2NaBr. An alkyl group attaches directly to the benzene ring. toluene (methylbenzene) Alcohols, Phenols and Ethers . Aldehydes, Ketones and Carboxylic Acids . Amines . The 10 chapters of Class 12 Chemistry . CBSE does not give marks to one chapter. It prints 6 marks for Unit 6, Haloalkanes and Haloarenes, which includes Haloalkanes and Haloarenes. No. They are written by SwaVid from the NCERT textbook. The CBSE curriculum is the reference for what is assessed. Alcohols, Phenols and Ethers. SwaVid is an AI tutor for Indian students in Classes 6 to 12. It finds the earlier ideas a child missed, then teaches today’s chapter. Start free to see how it works. - Unit 6 NCERT book - 6 marks, Unit 6 - 3 quick checks - Predicting SN1 substitution product for primary alkyl halides . Primary alkyl halides undergo substitution predominantly via the SN2 pathway because primary carbocations are unstable and steric hindrance is minimal. - Writing an alkyl cyanide when haloalkane reacts with silver cyanide . KCN is ionic and attacks mainly through carbon to form alkyl cyanides, but AgC≡N is largely covalent and attacks through nitrogen to form alkyl isocyanides (R-NC). - Expecting high nucleophilic reactivity for chlorobenzene at room temperature . Chlorobenzene is stabilized by resonance giving partial double-bond character to the C-Cl bond; nucleophilic substitution requires extreme conditions or strong electron-withdrawing groups. - Preparing Grignard reagents in the presence of water or moisture . Grignard reagents are highly reactive bases and react with any source of proton to form hydrocarbons, so they must be prepared in strictly anhydrous dry ether. ## Key Links - [CBSE](https://www.swavid.com/cbse) - [Class 12](https://www.swavid.com/cbse/class-12) - [Chemistry](https://www.swavid.com/cbse/class-12/chemistry/chapters) - [Start free →](https://www.swavid.com/signup) - [All 10 chapters](https://www.swavid.com/cbse/class-12/chemistry/chapters) - [NCERT Chemistry Part II (Reprint 2026-27)](https://ncert.nic.in/textbook.php) - [Open notes](https://www.swavid.com/cbse/class-12/chemistry/chapter/alcohols-phenols-and-ethers) - [Open notes](https://www.swavid.com/cbse/class-12/chemistry/chapter/aldehydes-ketones-and-carboxylic-acids) - [Open notes](https://www.swavid.com/cbse/class-12/chemistry/chapter/amines) - [Class 12 Chemistry](https://www.swavid.com/cbse/class-12/chemistry/chapters) - [Start free →](https://www.swavid.com/signup)