Question

Which from following statements is NOT correct for heterolysis?

• A. In this electron rich and electron deficient species are formed.
• B. Heterolysis of methyl bromide forms methyl carbocation.
• C. It occurs when bonded atoms have different electronegativity.
• D. Movement of a single electron from a shared pair of covalent bond occurs.

Hint:

Associate the terms clearly:
Homolysis = Homogeneous distribution = Single-electron movement $\rightarrow$ Free Radicals.
Heterolysis = Heterogeneous distribution = Two-electron pair movement $\rightarrow$ Ions.
Therefore, single electron movement can never be associated with heterolysis.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question asks us to identify the incorrect statement regarding heterolytic cleavage (heterolysis) of a covalent bond among the four options provided.

Step 2: Key Formula or Approach:
Covalent bonds can break in two distinct pathways:
1. Homolytic cleavage (Homolysis): The shared electron pair is split equally, where each leaving atom takes exactly one single electron, generating neutral free radicals. This involves the movement of a single electron represented by fish-hook arrows.
2. Heterolytic cleavage (Heterolysis): The shared electron pair is split unequally, where the more electronegative atom takes both bonding electrons, forming an anion (electron-rich) and a cation (electron-deficient). This involves a full-headed arrow representing a two-electron transfer.

Step 3: Detailed Explanation:
Let's analyze each statement systematically:
Statement (A): "In this electron rich and electron deficient species are formed." This is completely correct, as heterolysis splits a neutral molecule into an electron-deficient cation and an electron-rich anion.
Statement (B): "Heterolysis of methyl bromide forms methyl carbocation." This is entirely correct. Since bromine is much more electronegative than carbon, the C-Br bond undergoes heterolysis to yield a positive methyl carbocation ($\text{CH}_3^+$) and a bromide anion ($\text{Br}^-$).
Statement (C): "It occurs when bonded atoms have different electronegativity." This is correct because an electronegativity difference assists one atom in drawing the shared pair completely toward itself.
Statement (D): "Movement of a single electron from a shared pair of covalent bond occurs." This statement is incorrect. Heterolysis involves the transfer of both electrons (the entire pair) to one atom, whereas single-electron shifts occur exclusively in homolytic cleavage.

Step 4: Final Answer:
The incorrect statement is option (D), making it our correct choice.