Question

3-Phenylpropene on reaction with HBr in presence
of a peroxide gives
(1) 2-Bromo-3-phenylpropane
(2) 1-Phenyl-3-bromopropane
(3) 1-Bromo-3-phenylpropane
(4) 3-Bromo-1-phenylpropane​

Answer 1

Explanation:

3-Phenylpropene on reaction with HBr in presence of a peroxide gives

(1) 2-Bromo-3-phenylpropane ✔

(2) 1-Phenyl-3-bromopropane

(3) 1-Bromo-3-phenylpropane

(4) 3-Bromo-1-phenylpropane

Explaination :-

When 3-phenylpropene reacts With HBr in presence of peroxide then it gives 2-bromo-3-phenylpropane. This is the example of Anti-Markovnikov's rule or Kharasch's effect.

Additional information :-

Markovnikov's rule :-

→ Markovnikov's rule say that hydrogen is attached where hydrogen is more and halogen is attached where hydrogen is less.

Anti-Markovnikov's rule :-

→ Anti-Markovnikov's rule say that hydrogen is attached where hydrogen is less and halogen is attached where hydrogen is more.

→ Anti-Markovnikov's rule is also known as Kharasch's effect or peroxide effect.

Finkelstein reaction :-

→ Alkyl iodide are often prepared by the reaction of alkyl chloride/bromide with NaI in dry acetone. This reaction is known as Finkelstein reaction.

Sandmeyer's reaction :-

→ The diazonium salt is prepared by treating aniline dissolved in cold aqueous mineral acid with an aqueous solution of sodium nitrite at low temperature (0-5°C).

→ Bromo and chloroarenes can be prepared by treating a freshly prepared diazonium salt solution with cuprous bromide or cuprous chloride.

By the action of Thinoyl chloride :-

→ Chloroalkane is prepared by refluxing the alcohols with SOCl2 in the presence of pyridine.

→ Best method for preparation of Chloroalkane.