Problem 9 - A Complete Resource Book in Chemistry for JEE Main

Question

Which pair of species given below produce bakelite? (a) phenol, methanol (b) phenol, \(\mathrm{NaOH}\) (c) phenol, urea (d) phenol, formaldehyde

Step-by-Step Solution

Answer

Option (d), phenol and formaldehyde, is used to produce Bakelite.

Step 1: Understanding Bakelite

Bakelite is a type of early plastic that was one of the first synthetic polymers. It is produced by the condensation reaction between phenol and an aldehyde or ketone.

Step 2: Identifying the Reactants

Based on the given answers: - Option (a) involves phenol and methanol - Option (b) involves phenol and sodium hydroxide - Option (c) involves phenol and urea - Option (d) involves phenol and formaldehyde.

Step 3: Recognizing the Correct Reaction Pair

Bakelite is specifically made by the reaction of phenol with formaldehyde. None of the other options include formaldehyde; they involve either an alcohol, a base or a different nitrogen-containing compound.

Step 4: Conclusion

The pair that produces Bakelite is phenol and formaldehyde, which is option (d).

Key Concepts

Condensation Reaction

In the realm of chemistry, a condensation reaction is a crucial chemical process. It typically involves the combination of two molecules to form a larger molecule. During this process, a small molecule, often water, is removed or released. This is a vital step in the formation of many polymers and larger organic structures.
Bakelite synthesis, specifically, relies on a condensation reaction between phenol and formaldehyde. In this reaction, phenol and formaldehyde molecules join together to create the polymer network that gives Bakelite its unique properties.

• Two molecules combine to form a larger one.
• Often releases a small molecule, such as water.
• Essential for forming polymers like Bakelite.

Phenol

Phenol is an aromatic compound with the chemical formula C₆H₅OH. It is known for having a hydroxyl group (-OH) directly bonded to a benzene ring. This structure makes phenol a key reactant in many industrial chemical processes.
In the context of Bakelite synthesis, phenol plays a vital role due to its ability to readily undergo condensation reactions with other compounds, such as formaldehyde. The aromatic nature of phenol contributes to the stability and thermal resistance of the resulting Bakelite polymer.

• Chemical formula: C₆H₅OH
• Aromatic structure with a hydroxyl group
• Key reactant in Bakelite synthesis

Formaldehyde

Formaldehyde is a simple aldehyde with the formula CH₂O. It is a colorless gas at room temperature, characterized by a strong odor. In chemistry, formaldehyde is a potent and versatile reactant. Due to its reactivity, formaldehyde easily reacts with phenol in condensation reactions, forming a polymer network essential for Bakelite production. The reaction helps create strong, durable bonds that contribute to the hardness and heat resistance seen in Bakelite.

• Simple aldehyde: formula CH₂O
• Highly reactive, enabling effective polymerization
• Crucial for Bakelite's bond structure

Synthetic Polymers

Synthetic polymers are human-made polymers derived from petrochemicals or other chemical processes. These long chains of repeated units form a wide variety of materials with diverse applications, from plastics to clothing fibers. Bakelite represents one of the earliest synthetic polymers, showcasing the potential of combining phenol and formaldehyde. The resulting material is hard, heat-resistant, and non-conductive, making it invaluable in electrical insulators and the early manufacturing of consumer goods.

• Man-made polymers from chemical processes
• Include materials like plastics, fibers, and resins
• Bakelite: an early example with unique properties