7.5 Some Commercially Important Alcohols 😎

🎯 Quick Overview

Only two alcohols dominate industry and exams alike—methanol (CH3OH) and ethanol (C2H5OH). They power everything from paints to perfumes, so mastering their prep, properties and pitfalls is a must! :contentReference[oaicite:0]{index=0}

🚀 Methanol (CH3OH)

How it’s made

  • Old-school: destructive distillation of wood (hence the nickname “wood spirit”).
  • Modern route: catalytic hydrogenation of carbon monoxide at high P and T using a ZnO–Cr2O3 catalyst:
    \\( \mathrm{CO + 2H_2 \xrightarrow[\text{high }P,T]{ZnO\!-\!Cr_2O_3} CH_3OH} \\)

Key properties 🔍

  • Colourless liquid, b.p. 337 K.
  • Extremely poisonous—tiny sips can cause blindness; larger doses are fatal. ⚠️

Top uses 💼

  • High-grade solvent for paints & varnishes.
  • Feed-stock for making formaldehyde and many other chemicals.

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🌟 Ethanol (C2H5OH)

1️⃣ Fermentation route 🍇➡️🍷

  1. Invertase converts sucrose in molasses, sugarcane or grapes into glucose & fructose (\\( \mathrm{C_6H_{12}O_6} \\)).
  2. Zymase (from yeast) ferments these sugars under anaerobic conditions:
    \\( \mathrm{C_6H_{12}O_6 \xrightarrow{\text{zymase}} 2C_2H_5OH + 2CO_2} \\)
  3. Fermentation stops once alcohol reaches ≈14 %; above that, zymase is inhibited.
  4. If air leaks in, ethanol oxidises to ethanoic acid—ruining the drink’s taste.

2️⃣ Hydration route 🚰

Ethene hydration (see 7.4) now supplies bulk ethanol:
\\( \mathrm{CH_2{=}CH_2 + H_2O \xrightarrow{\text{acid}} C_2H_5OH} \\)

Properties 🔍

  • Colourless liquid, b.p. 351 K.
  • “Denatured” by adding CuSO4 (blue colour) + pyridine (foul odour) so people can’t drink industrial stocks.

Physiological effects 🧠

  • Acts on the central nervous system.
  • Small doses lower inhibitions; higher doses cause nausea, unconsciousness, and—at very high levels—can halt breathing.

Main uses 💼

  • Widely used solvent (e.g., paints).
  • Starting material for countless carbon compounds.

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💡 High-Yield NEET Nuggets

  1. Industrial methanol synthesis via catalytic hydrogenation of CO using ZnO–Cr2O3.
  2. Fermentation enzymes: invertase (sucrose → glucose + fructose) and zymase (glucose/fructose → ethanol + CO2).
  3. 14 % rule: zymase stops working when ethanol concentration exceeds ≈14 %.
  4. Denaturation cocktail for ethanol: CuSO4 + pyridine.
  5. Methanol toxicity—blindness at low doses, death at higher doses.

Happy studying and stay safe with those alcohols! 🎉