Test: JEE Main 35 Year PYQs- Haloalkanes & Haloarene- 2 - JEE MCQ

TIPS/Formulae :
The given reaction is an example of electrophilic substitution. Further, CH₃ group in toluene is o, p-directing

Chlorination beyond monochlorination during the preparation of alkyl halides in presence of UV light can be suppressed by taking alkane in excess.
NOTE : For isomeric alkanes the one having largest straight chain has highest b.p. because of large surface area.

Further dehydrohalogenation of CH₃CH = CH₂ can be done only by strong base like NaNH₂

Addition of HBr of 2-pentyne gives two structural isomers (I) and (II)

Each one of these will exist as a pair of geometrical isomers. Thus, there are two structural and four configurational isomers

NOTE : Alkyl halides give alcohols with aq. KOH, which is a substitution reaction.

TIPS/Formulae :
The reaction proceeds via free radical mechanism.
As 2º free radical is more stable than 1º, so
CH₃CH₂CH(Br)CH₃ would be formed.

(CH₃ )₃C -MgCl + D₂O → (CH₃)₃C -D +Mg(OD)Cl

Occurrence of racemization points towards the
formation of carbocation as intermediate, which being planar can be attacked from either side.

Dehydrobromination by strong base (alc. NaOH) followed by Markownikoff addition of HBr.

So F can have three possible structures

TIPS/Formulae :
It is an example of intramolecular Wurtz reaction.

NOTE : Br^– is a better leaving group than chloride. In this reaction alkali metal (Na) is electron donor.

Grignard reagents react with compounds containing active hydrogen to form hydrocarbons corresponding to alkyl (or aryl) part of the Grignard reagent.
C₆H₅MgBr + Me₃COH →C₆H₆ + Me₃COMgBr

NOTE : Elimination of HBr from CH₂= CHBr requires a stronger base because here, Br acquires partial double bond character due to resonance.

The product (a) will be formed.
Nucleophilic substitution of an alkyl halide is easier as compared to that of an aryl halide.
PhS^– is a strong nucleophile and dimethyl formamide  is a highly polar aprotic solvent.
These reagent favour S_N2 reactions at 2° benzylic carbon.
NOTE : In a S_N2 reaction, the major product formed is inversion product.

TIPS/Formulae :
Aryl halides are stable due to resonance stabilization.
The resonating structures

stabilise the aryl halide. These structures include a double bond between C and Cl which is shorter and thus stronger than the usual C – Cl single bond. The sp² hybridised carbon, being electronegative, makes the C – Cl bond shorter and stronger.

SOCl₂​,SO₂​Cl₂​ both give chlorination by nucleophilic substitution on an electrophilic carbon.

In toulene ,there is no electrophilic centre

oxidation occur by controlled free radical reaction using Cl₂​ in presence of high.