Phenol and phenolic resins — key facts Which of the following statements about phenol and phenol–formaldehyde products are correct in basic building-materials practice?
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APhenol is carbolic acid (common name).
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BPhenol is obtained from coal tar or synthesized from benzene.
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CPhenol reacts with formaldehyde to form phenol–formaldehyde resin.
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DPhenol–formaldehyde plastics find use in paints, varnishes, and items such as toilet seats.
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EAll of the above.
Answer
Correct Answer: All of the above.
Explanation
Introduction / Context:Phenol and phenolic resins occupy a central place in early polymer chemistry and building materials. Phenolic binders and finishes have been used in laminates, adhesives, and protective coatings for decades due to their heat resistance and durability.
Given Data / Assumptions:
- Nomenclature: “carbolic acid” is the historic name for phenol.
- Feedstocks: phenol has been produced from coal tar fractions or petrochemical routes (e.g., cumene process from benzene).
- Resin formation: phenol reacts with formaldehyde to yield thermosetting resins (resols/novolacs).
Concept / Approach:All statements trace the pathway from basic phenol sourcing to polymerization chemistry, and finally to practical uses in the built environment. Phenolic resins cure to hard, heat-resistant materials that serve in coatings, moulded parts, and laminates.
Step-by-Step Solution:
Identify phenol’s identity → carbolic acid is its common name.Recognize industrial sources → coal tar extraction or synthesis from benzene.Note reaction with formaldehyde → formation of phenol–formaldehyde resin.Connect to applications → paints, varnishes, moulded goods (e.g., toilet seats, handles).Verification / Alternative check:Historic materials catalogs and polymer handbooks document phenolic resins under trade names (e.g., Bakelite) with widespread building-related applications.
Why Other Options Are Wrong:
- Since A–D are correct, the best single choice is “All of the above.”
Common Pitfalls:Confusing thermosetting phenolics with thermoplastics; once cured, phenolics do not soften on reheating. Also, modern low-VOC coatings may use alternative chemistries, but the fundamentals remain instructive.
Final Answer:
All of the above.