JEE Main 35 Year PYQs- Haloalkanes & Haloarenes- 1 - Free MCQ Test

Since benzyl iodide gives yellow ppt. hence this is compound B and A was phenyl iodide (C₆H₅I).

DDT is prepared by heating chlorbenzene and chloral with concentrated sulphuric acid

In an SN2 reaction, in the transition state, there will be five groups attached to the carbon atom at which reaction occurs. 

Thus there will be crowding in the transition state, and presence of bulky groups make the reaction sterically hindered.

In Corey House synthesis of alkanes alkyl halide react with lithium dialkyl cuprate

R'X + LiR 2Cu → R'-R + RCu + LiX

The formation of 2-butene is in accordance to
Saytzeff’s rule. The more substituted alkene is formed. 

CH₃OH + C₆H₅MgBr → CH₃O.MgBr + C₆H₆

It follows E2 mechanism. Hughes and Ingold proposed that bimolecular elimination reactions take place when the two groups to be eliminated are trans and lie in one plane with the two carbon atoms to which they are attached i.e. E2 reactions are stereoselectively trans.

In S_N2 mechanism transition state is pentavelent. For bulky alkyl group it will have sterical hinderance and smaller alkyl group will favour the S_N2 mechanism. So the decreasing order of reactivity of alkyl halides is
RCH₂X > R₂CHX > R₃CX

S_N2 reaction is favoured by small groups on the carbon atom attached to halogen.
So, the order of reactivity is
CH₃Cl > (CH₃)₂CHCl > (CH₃)₃CCl > (C₂H₅)₂CHCl

NOTE : S_N2 reaction is shown to maximum extent by primary halides. The only primary halides given is CH₃Cl. so the correct answer is (d).

Since S_N1 reactions involve the formation of
carbocation as intermediate in the rate determining step, more is the stability of carbocation higher will be reactivity of alkyl halides towards S_N1 route. Now we
know that stability of carbocations follows the order :
3° > 2° > 1°, so S_N1 reactivity should also follow the same order.
3° > 2° > 1° > Methyl (S_N1 reactivity)

Four monochloro derivatives are chiral

DDT is a non-biodegradable pollutant.

Steric congestion around the carbon atom undergoing the inversion process will slow down the S_N2 reaction,
hence less congestion faster will the reaction. So, the order is
CH₃Cl > (CH₃)CH₂ – Cl > (CH₃)₂CH – Cl > (CH₃)₃CCl

Alkyl fluorides are more conveniently prepared by heating suitable chloro – or bromo-alkanes with organic fluorides such as AsF₃, SbF₃, CoF₂, AgF, Hg₂F₂ etc.
This reaction is called Swarts reaction.
CH₃Br + AgF → CH₃F + AgBr
2CH₃CH₂Cl + Hg₂F₂ →2CH₃CH₂F + Hg₂Cl₂