Problem 57 - A Complete Resource Book in Chemistry for JEE Main

Question

The distillation of phenol with zinc dust gives (a) \(\mathrm{C}_{6} \mathrm{H}_{5}-\mathrm{C}_{6} \mathrm{H}_{5}\) (b) \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{OC}_{6} \mathrm{H}_{5}\) (c) \(\mathrm{C}_{6} \mathrm{H}_{6}\) (d) \(\mathrm{C}_{6} \mathrm{H}_{12}\)

Step-by-Step Solution

Answer

The product is benzene, \( \mathrm{C}_6\mathrm{H}_6 \).

Step 1: Understanding the Reaction

Phenol is represented by the chemical formula \( \mathrm{C}_6\mathrm{H}_5\mathrm{OH} \). When phenol is heated with zinc dust, a reduction reaction occurs, which removes the oxygen attached to the phenol, effectively reducing the phenol to its simpler hydrocarbon form.

Step 2: Identify the Reaction Type

The reaction of phenol with zinc dust is a type of reduction reaction. Zinc serves as the reducing agent, which helps remove the oxygen atom from the phenol molecule, leading to the formation of benzene, \( \mathrm{C}_6\mathrm{H}_6 \).

Step 3: Predict the Reaction Product

In this reaction, zinc dust reduces phenol to benzene by removing the oxygen atom in the form of zinc oxide. This means the expected product of phenol distillation with zinc dust is benzene \( \mathrm{C}_6\mathrm{H}_6 \).

Key Concepts

zinc dust reduction

Zinc dust reduction is a popular technique in organic chemistry, used to convert phenolic compounds into hydrocarbons. This reduction process involves zinc dust as a reducing agent. When phenol

• has the chemical structure of \( \mathrm{C}_6\mathrm{H}_5\mathrm{OH} \)
• is heated in the presence of zinc dust

The oxygen atoms in the phenolic structure are removed. This type of reaction is essential because it transforms phenol into a less complex molecule by detaching the oxygen, thus eliminating the OH group from phenol.
Zinc itself, acting as a reducing agent, donates electrons to phenol. Often, students find it helpful to think of zinc as a helper that strips away the oxygen by forming zinc oxide \( (\mathrm{ZnO}) \) with this element, leaving behind pure hydrocarbons. This process emphasizes the versatile use of metal dust in chemistry, being an effective reductant even in seemingly stable molecules like phenol.
Overall, mastering zinc dust reduction opens doors to understanding more about hydrocarbon synthetization and reaction mechanisms in organic chemistry.

benzene formation

Benzene formation from phenol through zinc dust reduction is a fundamental concept in organic chemistry. Benzene is a simple aromatic hydrocarbon with the formula \( \mathrm{C}_6\mathrm{H}_6 \), characterized by its ring structure with alternating double and single bonds, creating a stable resonance system.
In this reaction, phenol's hydroxyl group (\( \mathrm{OH} \)) is detached, leading to the reformation of the benzene ring.

• This reaction removes just the oxygen atom.
• It ensures no other substitutions or structural changes in the carbon framework.

The transformation of phenol to benzene is not just about changing a formula. It’s about understanding how the specific removal of one atom, facilitated by a reducing agent like zinc, leads to the formation of a simpler and more stable hydrocarbon.
This reaction underscores the importance of benzene in chemistry due to its foundation for more complex aromatic structures. Understanding benzene formation helps chemists deduce subsequent reaction pathways in complex organic syntheses, making it an essential part of the organic chemistry toolkit.

organic chemistry reactions

Organic chemistry reactions are a diverse and vast field, encompassing different mechanisms and transformations like addition, substitution, and reduction. The reduction of phenol to benzene is a classic example of how selective elimination of certain atoms and groups can yield a different product entirely.
Reduction reactions involve the gain of electrons, often facilitated by reducing agents like zinc. In zinc dust reduction, the goal is to simplify a molecule, retaining only the core hydrocarbon structure.

• Phenolic compounds serve as excellent models for studying these transformations.
• The reaction highlights how complex molecules can be broken down in a controlled manner.

Organic reactions don’t just end with the transformation. They extend to understanding mechanisms, predicting products, and applying these reactions in synthetic chemistry to build larger, more complex molecules from simpler ones.
The study of these reactions not only enhances comprehension of chemical processes but also equips students with the knowledge to approach real-world problems via organic synthesis methods. A thorough grasp of reactions like zinc dust reduction is crucial for organic synthesis, pharmaceutical development, and chemical engineering solutions.