Statements on Hydrohalogenation and Preparation of Aryl Compounds
Given below are two statements:
Statement I: 3-phenylpropene reacts with 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
Options
Both Statement I and Statement II are true
Both Statement I and Statement II are false
Statement I is true but Statement II is false
Statement I is false but Statement II is true
Topics & Concepts
Step-by-Step Solution
To determine the correctness of both statements, let us analyze them step-by-step:
Evaluation of Statement I:
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Structure of Reactant: 3-phenylpropene has the molecular formula .
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Electrophilic Addition Mechanism ():
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Step 1: Protonation The double bond undergoes electrophilic addition with to form a secondary carbocation:
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Step 2: Rearrangement via 1,2-Hydride Shift The secondary carbocation rearranges via a -hydride shift to form a more stable benzylic carbocation, which is stabilized by resonance with the aromatic ring:
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Step 3: Nucleophilic Attack by The bromide ion attacks the benzylic carbocation to form the major product:
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Product Characteristics:
- The major product is 1-bromo-1-phenylpropane.
- The carbon attached to the bromine atom is bonded to two other carbon atoms (the benzylic ring carbon and the ethyl group carbon), making it a secondary alkyl bromide.
- The carbon atom () in is bonded to four distinctly different groups: , , , and . Hence, it is a chiral carbon atom.
Therefore, Statement I is true.
Evaluation of Statement II:
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Sandmeyer Reaction: Benzenediazonium chloride reacts with cuprous salts like , , and to give aryl chlorides (), aryl bromides (), and aryl cyanides (), respectively.
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Gattermann Reaction: In the Gattermann reaction, copper powder in the presence of the corresponding halogen acid ( or ) is used to prepare aryl chlorides and aryl bromides: However, aryl cyanides () cannot be prepared by the Gattermann reaction.
Therefore, Statement II is false.
Conclusion:
- Statement I is true
- Statement II is false
This corresponds to Option C.