Question

Given below are two statements:

Statement I: 3-phenylpropene reacts with $HBr$ and gives secondary alkyl bromide having a chiral carbon atom as the major product.

Statement II: Aryl chlorides and aryl cyanides can be prepared by Sandmeyer reaction as well as Gattermann reaction.

In the light of the above statements, choose the correct answer from the options given below

• A. Both Statement I and Statement II are true
• B. Both Statement I and Statement II are false
• C. Statement I is true but Statement II is false
• D. Statement I is false but Statement II is true

Hint:

Think about carbocation rearrangement to the more stable benzylic position for the first statement. For the second, distinguish the reagents used in Sandmeyer and Gattermann reactions, specifically regarding cyanide.

Answer 1

The Correct Option is C

Let's evaluate the statements based on organic chemistry principles.

Analysis of Statement I:
1. Reactant: 3-phenylprop-1-ene ($Ph-CH_2-CH=CH_2$).
2. Reagent: $HBr$.
3. Mechanism: Electrophilic addition. The first intermediate is a secondary carbocation ($Ph-CH_2-CH^+-CH_3$). A 1,2-hydride shift occurs to form a secondary benzylic carbocation ($Ph-CH^+-CH_2-CH_3$), which is resonance-stabilized by the benzene ring.
4. Major Product: $Ph-CH(Br)-CH_2-CH_3$ (1-bromo-1-phenylpropane).
5. Characterization: This is a secondary alkyl bromide. The carbon atom attached to the $Br$ atom is bonded to four different groups ($-H$, $-Br$, $-C_2H_5$, $-C_6H_5$), making it chiral. Thus, Statement I is correct.

Analysis of Statement II:
1. Sandmeyer Reaction: Converts diazonium salts to $Ar-Cl$, $Ar-Br$, or $Ar-CN$ using $Cu(I)$ salts like $CuCl$, $CuBr$, or $CuCN$. This is true.
2. Gattermann Reaction: A modification using $Cu$ powder and $HX$ to produce $Ar-Cl$ or $Ar-Br$. It does not typically apply to the synthesis of aryl cyanides ($Ar-CN$), for which the Sandmeyer method is used. Thus, the statement is incorrect in claiming Gattermann can be used for aryl cyanides. Statement II is false.

Conclusion: Statement I is True, Statement II is False.