Haloalkanes and Haloarenes — Class 12 CBSE Chemistry revision notes
A 5-page visual revision sheet for Haloalkanes and Haloarenes, written for Class 12 CBSE Chemistry. Formulas, diagrams and the traps that cost marks, laid out to be read the night before rather than the term before. Free, and it opens inside CapCompass.
Page 1 as PDF
Haloalkanes and Haloarenes in one look
a halogen on carbon sets up a leaving group, and everything else follows from how well it leaves
Haloalkane vs haloarene
- halogen on an sp^3 carbon, e.g. CH_3CH_2Cl
- C-X bond is a normal sigma bond, halogen lone pairs not delocalised
- undergoes nucleophilic substitution readily
- halogen on an sp^2 aromatic carbon, e.g. chlorobenzene
- halogen lone pair conjugates into the ring, C-X gets partial double-bond character
- resists nucleophilic substitution under ordinary conditions, needs forcing conditions
Classification and nomenclature
- primary (1°): halogen carbon attached to one other carbon; secondary (2°): two; tertiary (3°): three
- allylic halide: halogen on the carbon next to a C=C double bond; benzylic halide: halogen on the carbon next to an aromatic ring
- IUPAC name treats halogen as a substituent prefix: chloro, bromo, iodo, fluoro, cited alphabetically with other substituents
- vinylic halide: halogen directly ON a double-bond carbon (C=C-X); like aryl halides, this C-X also resists substitution
Common preparation routes
- from an alcohol, SOCl_2 (best: only gases as byproducts)
R-OH+SOCl_2→ R-Cl+SO_2+HCl - from an alkene, HX addition (Markovnikov)
R-CH=CH_2+HX→ R-CHX-CH_3 - from an alkane, free-radical halogenation under UV light
R-H+X_2to R-X+HX
Page 1 of 5. The full sheet, all 5 pages, opens free in the app.
What this Haloalkanes and Haloarenes sheet covers
- Haloalkane vs haloarene
- Haloalkane (alkyl halide)
- Haloarene (aryl halide)
- Classification and nomenclature
- Common preparation routes
- from an alcohol, SOCl_2 (best: only gases as byproducts)
- from an alkene, HX addition (Markovnikov)
- from an alkane, free-radical halogenation under UV light
- SN1 vs SN2 mechanism
- SN1
- SN2
- Predicting SN1 vs SN2
- Why haloarenes resist nucleophilic substitution
- Elimination vs substitution with a bulky base
- Other named reactions
- Wurtz reaction: two alkyl halides + sodium in dry ether
- Fittig reaction: two aryl halides + sodium in dry ether
- Friedel-Crafts alkylation, catalysed by AlCl_3
- Grignard reagent
- Polyhalogen compounds, uses and cautions
- Symbols
- Traps that cost marks
- Tricks that save time
How CapCompass uses this sheet
These notes are not a standalone PDF. CapCompass plans Chemistry chapter by chapter against your real exam dates and free hours, and when the plan reaches Haloalkanes and Haloarenes the sheet opens inside the study block itself — at the page covering the sub-topic that block is on, with the timer still running. Revision arrives at the moment the plan says revise, instead of having to be gone looking for.