JEE · Chemistry · Haloalkanes & Haloarenes doubts
12 doubts found
How do I decide whether a reaction will go by SN1 or SN2?
Look at the substrate first.
Why were CFCs banned for damaging the ozone layer?
Chlorofluorocarbons are so unreactive they drift up to the stratosphere intact.
Why must a Grignard reagent be made and used in perfectly dry conditions?
A Grignard reagent (R–MgX) has a strongly nucleophilic, basic carbon.
Why does a tertiary halide give a racemic (mixed left/right) product while a primary one gives a single mirror image?
A tertiary halide reacts by SN1 through a flat, planar carbocation.
What does “Nucleophilic substitution” actually mean in Haloalkanes & Haloarenes, and why does it matter for JEE?
a nucleophile replaces the halogen; it can go by SN1 (two steps, via a carbocation) or SN2 (one step, backside attack).
I keep getting “Nucleophilic substitution” questions wrong in Haloalkanes & Haloarenes. What's the trap?
assuming every substrate reacts by the same mechanism.
What does “Grignard reagent” actually mean in Haloalkanes & Haloarenes, and why does it matter for JEE?
R–MgX is a powerful nucleophile/base that builds C–C bonds, but it reacts violently with any water.
I keep getting “Grignard reagent” questions wrong in Haloalkanes & Haloarenes. What's the trap?
using a Grignard reagent in a wet apparatus.
What is the difference between polar protic solvent and polar aprotic solvent?
A polar protic solvent (water, alcohols) can hydrogen-bond, stabilising a carbocation, so it favours SN1; a polar aprotic solvent (acetone, DMSO) leaves the nucleophile free and reactive, so it favours SN2.
What is the difference between haloalkane and haloarene?
A haloalkane has halogen on an sp³ carbon and readily undergoes substitution; a haloarene has halogen on an aromatic ring where resonance and the sp² C–X bond make substitution much harder.
How is Haloalkanes & Haloarenes tested in JEE, and what should I focus on?
Prioritise the core ideas: Nucleophilic substitution, Grignard reagent.
What are the most common mistakes students make in Haloalkanes & Haloarenes?
the halogen on an aromatic ring is held by partial double-bond (resonance) character, so haloarenes resist the easy substitution that haloalkanes undergo.