Question

Observe the following compounds and answer the questions given below.

      (I)

\[\ce{\underset{\text{(II)}}{CH3 - CH2 - Br}}\]

1. Identify the type of halides.
2. Explain the nature of the C – Br bond in both of these halides.
3. Which of these compounds will undergo aqueous alkaline hydrolysis readily? Write the reaction in support of your answer.

Answer 1

1. I - Haloarene/Aryl halide
   II - Haloalkane/Alkyl halide
   
2. 1. In compound (I), the halogen atom (–Br) is directly bonded to the sp² hybridized carbon atom of the aromatic ring. One of the lone pairs of electrons on the Br atom is in conjugation with π-electrons of the ring.
   Due to resonance, the C – Br bond acquires partial double bond character. As a result, the C – Br bond in compound (I) is stronger and shorter than compound (II).
   2. In compound (II), the halogen atom (–Br) is bonded to sp³ hybridized carbon which is a part of the saturated carbon skeleton. The C – Br bond in compound (I) is a polar covalent bond as –Br is more electronegative than carbon.
3. Compound (II) will undergo aqueous alkaline hydrolysis readily. Aqueous alkaline hydrolysis of ethyl bromide can be given as,
   \[\ce{\underset{\text{Ethyl bromide}}{CH3CH2 - Br} + \underset{\text{Nucleophile}}{OH-} -> \underset{\text{Ethanol}}{CH3CH2 - OH} + \underset{\text{Bromide ion}}{Br-}}\]