Question

Match List-I with List -II

Choose the correct answer from the options given below:

• (A) - (II), (B) - (I), (C) - (III), (D) - (IV)
• (A) - (II), (B) - (I), (C) - (IV), (D) - (III)
• (A) - (III), (B) - (IV), (C) - (II), (D) - (I)
• (A) - (III), (B) - (IV), (C) - (I), (D) - (II)

Hint:

Key mechanism relationships:
\(\text{S}_\text{N}1 \rightarrow\) Planar carbocation \(\rightarrow\) Racemization.
\(\text{S}_\text{N}2 \rightarrow\) Backside displacement \(\rightarrow\) Walden Inversion.
\(\text{HX}\) addition \(\rightarrow\) Carbocation stability \(\rightarrow\) Markovnikov.
Hydroboration-oxidation \(\rightarrow\) Anti-Markovnikov addition of \(\text{H}_2\text{O}\).

Answer 1

The Correct Option is C

Concept:
Organic transformations show distinct stereochemical and regiochemical outcomes depending on the reaction mechanism, whether proceeding via planar carbocations, concerted backside displacement, or cyclic addition intermediates.

Step 1: Mechanism of Unimolecular Nucleophilic Substitution (\(\text{S}_\text{N}1\)):
The rate-determining step in an \(\text{S}_\text{N}1\) process is the departure of the leaving group to form a planar, \(sp^2\)-hybridized carbocation.
The incoming nucleophile can attack this planar intermediate from either face with equal probability.
For an optically active substrate, this attack leads to an equimolar mixture of enantiomers, resulting in racemization.
Therefore, (A) matches with (III).

Step 2: Electrophilic Addition of \(\text{HX}\) to Alkenes:
In the electrophilic addition of hydrogen halides to unsymmetrical alkenes, the electrophilic proton attaches to the carbon atom that already bears the greater number of hydrogen atoms.
This pathway proceeds via the more stable carbocation intermediate, yielding the Markovnikov product.
Therefore, (B) matches with (IV).

Step 3: Mechanism of Bimolecular Nucleophilic Substitution (\(\text{S}_\text{N}2\)):
An \(\text{S}_\text{N}2\) reaction proceeds via a single concerted step in which the nucleophile attacks from the side opposite to the leaving group.
This backside attack turns the tetrahedral geometry inside out, leading to complete inversion of configuration (Walden inversion).
Therefore, (C) matches with (II).

Step 4: Hydroboration-Oxidation of Alkenes:
Hydroboration-oxidation involves the concerted syn-addition of borane (\(\text{BH}_3\)) across a carbon-carbon double bond, followed by alkaline peroxide oxidation.
Boron bonds to the less hindered, less substituted carbon atom, which upon oxidation produces an alcohol with anti-Markovnikov regiochemistry.
Therefore, (D) matches with (I).
Final Answer:
The correct matching is (A)-(III), (B)-(IV), (C)-(II), (D)-(I), which corresponds to option (C).