Phenolic thermoset formation:\nCondensation polymerisation of which pair of reactants produces Bakelite (phenol–formaldehyde resin)?

Introduction / Context:
Bakelite is the archetypal thermosetting resin, formed by condensation of phenol with formaldehyde to yield a cross-linked network. Recognising the correct monomer pair distinguishes phenolic resins from other condensation systems like urea–formaldehyde or melamine–formaldehyde.

Given Data / Assumptions:

• Bakelite is the trade name associated historically with phenol–formaldehyde resins.
• Cross-linking occurs during cure, making the material infusible.

Concept / Approach:
Phenol reacts with formaldehyde under acidic or basic catalysis to form hydroxymethyl phenols and then methylene/methylene-ether bridges, ultimately creating a 3D network known as Bakelite. Other aldehyde–amine systems produce different thermosets (e.g., urea–formaldehyde), not Bakelite.

Step-by-Step Solution:

Verification / Alternative check:
Materials encyclopedias uniformly define Bakelite as the phenol–formaldehyde thermoset network.

Why Other Options Are Wrong:

• Propylene: forms polypropylene via addition.
• Phenol & acetaldehyde: not the standard pair for phenolic resins.
• Urea & formaldehyde: yields UF resins.

Common Pitfalls:
Confusing UF/MF with phenolics due to similar condensation chemistry; the phenolic monomer identity is key.

Final Answer:
Phenol & formaldehyde