Chemistry - Halogen Derivative Question with Solution | TestHub

(A) Rate of Sɴ1 Reaction

Answer: The statement is correct.

The rate of Sɴ1 reaction depends on the stability of the carbocation intermediate. Tertiary carbocations are more stable than secondary carbocations due to hyperconjugation and inductive effects. The stability order is $3^{\circ }>2^{\circ }>1^{\circ }>methyl$. The carbocation formed from the benzylic chloride (Ph₂CH-Cl) is highly stable due to resonance with two benzene rings, making it more reactive than the secondary cyclic carbocation. The order given is correct: secondary cyclic halide $<$ benzylic chloride.

(B) Rate of Sɴ2 Reaction

Answer: The statement is correct.

The rate of Sɴ2 reaction is inversely proportional to steric hindrance at the reaction center. The order given is primary halide with electron-withdrawing group $>$ allylic halide $>$ secondary halide. The primary halide with a ketone group has less steric hindrance than the allylic and secondary halides. Secondary halides have significant steric hindrance compared to primary and allylic halides, making the given order of reactivity correct.

(C) Aryl halide are less reactive than Alkyl halide for nucleophilic substitution reaction

Answer: The statement is correct.

Aryl halides are less reactive towards nucleophilic substitution reactions than alkyl halides due to several reasons:

The C-Cl bond in aryl halides has partial double bond character due to resonance, making it stronger and shorter. The carbon atom is $s{p}^2$ hybridized, which is more electronegative than the $s{p}^3$ carbon in alkyl halides, holding the electron pair more tightly. Steric hindrance and repulsion from the electron-rich benzene ring hinder the approach of the nucleophile.

(D) Benzene and propene can be distinguished by bromine water test

Answer: The statement is correct.

Propene is an alkene and will undergo an addition reaction with bromine water (Br₂ in H₂O), causing the reddish-brown color of the bromine water to decolorize. Benzene, although it has double bonds, is aromatic and does not typically undergo addition reactions under these mild conditions; it requires specific catalysts for substitution reactions. Therefore, the test can distinguish between them.