Ionic reactions with organic compounds proceed through:
(A) Homolytic bond cleavage
(B) Heterolytic bond cleavage
(C) Free radical formation
(D) Primary free radical
(E) Secondary free radical
Choose the correct answer from the options given below:
(A) Homolytic bond cleavage
(B) Heterolytic bond cleavage
(C) Free radical formation
(D) Primary free radical
(E) Secondary free radical
Choose the correct answer from the options given below:
- (A) only
- (C) only
- (B) only
- (D) and (E) only
The Correct Option is C
Solution and Explanation
The question asks to identify the fundamental process through which ionic reactions with organic compounds proceed from the given options.
Concept Used:
Organic reactions are classified based on how the covalent bonds are broken. There are two primary types of covalent bond cleavage:
- Homolytic Bond Cleavage (Homolysis): In this process, the shared pair of electrons in a covalent bond is distributed equally between the two separating atoms. This leads to the formation of highly reactive, neutral species with an unpaired electron, known as free radicals. \[ \text{A:B} \xrightarrow{\text{Homolysis}} \text{A}^\bullet + \text{B}^\bullet \] Reactions involving this type of cleavage are called free-radical reactions.
- Heterolytic Bond Cleavage (Heterolysis): In this process, the shared pair of electrons is transferred completely to one of the bonded atoms when the bond breaks. This results in the formation of a pair of oppositely charged ions: a cation and an anion. \[ \text{A:B} \xrightarrow{\text{Heterolysis}} \text{A}^+ + \text{:B}^- \quad (\text{if B is more electronegative}) \] Reactions involving the formation and reaction of these charged species (ions) are called ionic reactions.
Step-by-Step Solution:
Step 1: Analyze the term "Ionic Reactions".
By definition, an "ionic reaction" is a reaction that proceeds through ionic intermediates. These intermediates are charged species, such as carbocations (positively charged carbon atoms) or carbanions (negatively charged carbon atoms).
Step 2: Evaluate the bond cleavage required for ionic reactions.
For an ionic reaction to occur, charged intermediates must be formed from a neutral organic molecule. This requires the unequal breaking of a covalent bond, where one atom retains the entire bonding pair of electrons, becoming an anion, and the other atom loses the electrons, becoming a cation. This process is, by definition, heterolytic bond cleavage.
Step 3: Evaluate the given options.
- (A) Homolytic bond cleavage: This process forms free radicals, not ions. It is the basis for free-radical reactions, not ionic reactions.
- (B) Heterolytic bond cleavage: This process forms ions (cations and anions), which are the key intermediates in ionic reactions. This is the correct mechanism.
- (C) Free radical formation: Free radicals are the result of homolytic cleavage and are characteristic of free-radical reactions.
- (D) Primary free radical: This is a specific type of free radical, an intermediate in free-radical reactions.
- (E) Secondary free radical: This is also a specific type of free radical, an intermediate in free-radical reactions.
Therefore, options (A), (C), (D), and (E) all relate to free-radical mechanisms, while only option (B) correctly describes the bond-breaking mechanism essential for ionic reactions.
Final Result:
Ionic reactions are characterized by the involvement of charged intermediates (ions). The formation of these ions from covalent organic compounds occurs through the unequal breaking of a bond, which is known as heterolytic bond cleavage.
The correct answer is (B) Heterolytic bond cleavage.
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