Problem 13 - A Complete Resource Book in Chemistry for JEE Main

Question

The substance used in the preparation of malachite green is (a) benzaldehyde (b) acetone (c) formaldehyde (d) acetaldehyde

Step-by-Step Solution

Answer

The substance used is benzaldehyde.

Step 1: Understand the Exercise

The exercise is asking which substance is used in the preparation of malachite green. Malachite green is a synthetic dye and it is important to know the chemical process or compounds involved in its synthesis.

Step 2: Identify Relevant Chemical Processes

Malachite green is traditionally synthesized by a condensation reaction. This process usually involves an aromatic aldehyde and an aromatic amine.

Step 3: Analyze the Options Given

The options given in the question are: benzaldehyde, acetone, formaldehyde, and acetaldehyde. Benzaldehyde is an aromatic aldehyde, which aligns with the process of synthesizing dyes like malachite green.

Step 4: Select the Correct Option

Given the chemical synthesis process of malachite green, benzaldehyde is the substance that fits the criteria. Thus, the correct answer is option (a) benzaldehyde.

Key Concepts

Aromatic Aldehyde

Aromatic aldehydes are organic compounds that have an aldehyde group (-CHO) attached to an aromatic ring, usually a benzene ring. These compounds play a significant role in various chemical syntheses, including the production of dyes, perfumes, and pharmaceuticals.
Aromatic aldehydes are characterized by their distinct smells and are often used as flavoring agents in industry. The presence of the aromatic ring contributes to the stability and reactivity of these compounds.
In chemical reactions, aromatic aldehydes act as key intermediates. Their ability to participate in various organic reactions, including condensation reactions, makes them versatile and valuable for chemists.

Benzaldehyde

Benzaldehyde is a simple and widely known aromatic aldehyde. Its structure consists of a benzene ring attached to an aldehyde group. This makes it an important starting material in organic chemistry.
Benzaldehyde is used industrially for the synthesis of other chemicals. It is famously used in the production of the synthetic dye, malachite green, through reactions that involve the interaction of aromatic amines. In addition to dye synthesis, benzaldehyde serves as a precursor for perfumes, flavorings, and pharmaceuticals.
To RECAP:

• It is colorless with a characteristic almond-like aroma.
• It participates in many organic syntheses due to its reactivity with other compounds.
• It is a key component in malachite green creation.

Synthetic Dye

Synthetic dyes are man-made chemical compounds designed to provide color to materials. These dyes are used in a vast array of applications, from clothing to food and other consumer goods.
Synthetic dyes like malachite green are created through specific chemical reactions. The synthesis involves complex processes, one of which is the condensation reaction, where benzaldehyde is a critical component.
These dyes offer several advantages over natural dyes:

• They provide a wider range of colors and greater color fastness.
• They are more cost-effective and sustainable for industrial use.
• Their chemical structure can be specifically designed to meet processing needs.

This specificity and versatility make synthetic dyes indispensable in today's world.

Condensation Reaction

A condensation reaction is a chemical process where two molecules combine to form a single molecule, usually with the loss of a small molecule like water or hydrogen chloride. This type of reaction is key in organic synthesis.
In the creation of malachite green, a condensation reaction occurs between benzaldehyde and aromatic amines. This reaction is crucial because it forms the core structure of the dye.
Condensation reactions are central to forming various organic compounds and are highly valued in synthetic chemistry:

• They allow for the formation of complex molecules from simpler ones.
• They are used in the synthesis of polymers, resins, and, of course, dyes.

The versatility of these reactions underscores their importance in both laboratory and industrial settings.

Aromatic Amine

Aromatic amines are organic compounds consisting of an amine group (-NH2) attached to an aromatic ring. These compounds are significant due to their role in manufacturing dyes, drugs, and plastics.
Their structure gives them unique properties and reactivity, which are essential in forming synthetic dyes like malachite green. In the dye synthesis process, aromatic amines react with aromatic aldehydes in a condensation reaction.
Key points about aromatic amines:

• They are used extensively in the chemical industry for dye synthesis.
• Their chemical interactions are central to forming complex colorant molecules.
• They provide stability and enhance color properties in dyes.

Overall, aromatic amines are vital components in many industrial applications, especially in creating brilliant synthetic dyes.