From Structure to Function: A Quick Reminder

Before diving into real-world examples, take a moment to recall ideas from previous modules:

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Key Feature	What You Already Know	Why It Matters for Applications
O–H group in alcohols	Capable of hydrogen bonding	Raises boiling point, improves water solubility → useful for disinfectants that must mix with water
C–O–C linkage in ethers	Cannot form hydrogen bonds to each other; non-polar regions dominate	Low boiling point, good solvent for non-polar substances, often volatile
Combustion of small alcohols	Releases energy, produces CO₂ + H₂O	Alternative fuels and fuel additives
Oxidation reactions	Convert primary alcohols → aldehydes → carboxylic acids	Basis for breath alcohol tests and food preservative production
Relative stability of ethers	Less prone to many reactions	Chosen as inert solvents in sensitive chemical syntheses

Keep these connections in mind while you explore each field of use below.

5.2 Alcohols in Everyday Life

5.2.1 Household and Personal-Care Products

1. Hand Sanitizers

   • Active ingredient: Ethanol (60–95 %) or isopropanol (≈70 %).

   • Why these alcohols?

     • They dissolve bacterial and viral membranes.

     • They evaporate quickly without leaving a residue because of moderate boiling points.

     • They are miscible with water and skin conditioners such as glycerol.

2. Antifreeze and Windshield Washer Fluids

   • Active ingredient: Ethylene glycol or propylene glycol.

   • Properties used:

     • Very high boiling points and low freezing points, stemming from strong hydrogen bonding.

     • Mixed with water, they lower the freezing point of the mixture, preventing engine block damage.

   • Safety note: Ethylene glycol is toxic if swallowed; propylene glycol is chosen for “pet-safe” products.

3. Perfumes and Colognes

   • Solvent: Ethanol.

   • Reason: Ethanol dissolves many fragrance oils (non-polar) and also mixes with water, giving a clear, uniform spray that evaporates quickly, leaving the scent behind.

5.2.2 Food and Beverages

• Fermentation of sugars by yeast produces ethanol—the basis of beer, wine, and spirits.

• Sugar alcohols (e.g., sorbitol, xylitol) provide sweetness with fewer calories and a lower impact on blood glucose.

• Ethanol acts as a carrier for vanilla extract and other flavor concentrates because it can dissolve both water-soluble and fat-soluble flavor molecules.

5.2.3 Fuels and Energy

1. Gasoline Additives

   • Bioethanol (E10, E85 mixtures): Raises the octane number and burns cleaner than pure gasoline, reducing carbon monoxide emissions.

   • Energy content issue: Ethanol contains about 30 % less energy per liter than gasoline, so fuel economy can drop slightly at high ethanol blends.

2. Straight Alcohol Fuels

   • Methanol: Used in race cars and some industrial burners. Its simple structure allows very rapid combustion but also leads to toxicity; strict rules govern its use.

   • Butanol (future interest): Closer energy content to gasoline while still renewable if produced by fermentation.

5.2.4 Pharmaceuticals

• Solvents and Carriers: Ethanol dissolves many drug molecules that are not water-soluble.

• Active Agents:

  • Glycerol (glycerin) soothes sore throats in cough syrups.

  • Benzyl alcohol is used as a preservative in injectable medicines due to its mild antibacterial action.

5.3 Ethers in Everyday Life

5.3.1 Solvents in the Laboratory and Industry

1. Diethyl Ether

   • Very low boiling point (35 °C) due to minimal hydrogen bonding → evaporates quickly.

   • Low polarity means it dissolves many non-polar reactants but remains separate from water.

   • Common in extraction procedures and Grignard reactions (Module 4 refresher).

   • Hazard: Highly flammable; forms explosive peroxides on long storage with oxygen. Always test and discard old bottles safely.

2. Tetrahydrofuran (THF)

   • Cyclic ether with a slightly higher polarity than diethyl ether.

   • Useful for dissolving polymers such as PVC; serves as a reaction medium for organometallic chemistry.

3. 1,4-Dioxane

   • Good solvent for cellulose and many synthetic reactions.

   • Emerging environmental concern: Classified as a probable carcinogen, found near detergent manufacturing sites.

5.3.2 Medical Uses

1. Diethyl Ether as an Early Anesthetic

   • First public demonstration in 1846 (“Ether Day”).

   • Works by depressing the central nervous system.

   • Replaced in modern practice by safer, easier-to-control agents, yet its discovery revolutionized surgery.

2. Modern Inhalation Anesthetics

   • Enflurane, Isoflurane, Sevoflurane are halogenated ethers.

   • Ether structure gives the right balance of volatility and stability, enabling rapid control of patient sedation with minimal metabolism in the body.

5.3.3 Fuel Additives

• MTBE (methyl tert-butyl ether)

  • Introduced to boost octane and cut carbon monoxide emissions.

  • Withdrawn or restricted in many regions because of groundwater contamination and a foul taste in drinking water.

  • Offers a lesson on balancing performance with environmental impact.

5.4 Safety: Handling, Storage, and Environmental Impact

5.4.1 General Laboratory and Household Safety Rules

1. Ventilation

   • Work in a fume hood or open space whenever vapors could build up.

2. Personal Protective Equipment

   • Safety glasses, nitrile gloves, and a lab coat for liquid handling.

3. Fire Risks

   • Keep open flames away.

   • Store flammable liquids (ethanol, diethyl ether) in metal safety cabinets.

4. Spill Response

   • Absorb small spills with inert material like sand, then dispose of according to local rules.

5. Disposal

   • Do not pour ethers or concentrated alcohols down the sink. Collect in labeled waste bottles.

5.4.2 Specific Hazards

Compound	Main Risk	Best Practice
Methanol	Blindness, death if ingested	Use colored fuel to discourage drinking; store locked away
Diethyl Ether	Extremely flammable; peroxide formation	Purchase small bottles; test for peroxides before distillation
Ethylene Glycol	Sweet taste attracts pets/children; kidney failure	Add bittering agent; switch to propylene glycol when possible
Halogenated Ethers	Greenhouse gases, anesthetic overdose	Minimize leakage with closed systems; monitor patient breathing

5.4.3 Environmental Points

• Volatile Organic Compounds (VOCs): Both alcohols and ethers can contribute to urban smog if released in large amounts.

• Biodegradability: Ethanol breaks down fairly quickly; some ethers like MTBE persist longer.

• Renewability: Bio-based ethanol and butanol reduce dependence on petroleum, but crop land use must be balanced with food needs.

• Life-Cycle Analysis: Engineers now look at energy spent in farming, transport, and processing when rating a fuel’s true carbon footprint.

5.5 Economic and Social Importance

1. Global Production

   • Ethanol: >100 billion liters per year (fuel and beverage).

   • Propylene Glycol: Key intermediate in plastics, cosmetics.

   • Ether solvents: Thousands of tons annually for pharmaceuticals, agrochemicals, and paints.

2. Job Creation

   • Farming, fermentation plants, refinery blending, shipping, and retail sectors all rely on alcohol-based fuels.

   • Specialty chemical companies produce medical-grade ethers and employ chemists, engineers, and technicians.

3. Public Health Impact

   • Hand sanitizers cut infection rates in hospitals and public spaces, a fact highlighted during the 2020 health crisis.

   • Safe anesthetics enable painless surgery, extending life expectancy and quality of life worldwide.

5.6 Mini-Case Studies

Case Study A: Hand Sanitizer Shortage and Community Response

During the early months of 2020, demand for hand sanitizer outpaced supply. Local distilleries switched from beverage alcohol to sanitizer production almost overnight. Understanding the chemistry of denatured ethanol, glycerol (to stop skin drying), and hydrogen peroxide (to kill bacterial spores) allowed these small businesses to meet health guidelines quickly.

 

Questions for you:

1. Which property of ethanol ensures rapid drying on the skin?

2. Why is glycerol added even though it reduces the sanitizer’s volatility?

3. What role does hydrogen peroxide play, and why is only a small amount needed?

Case Study B: The Rise and Fall of MTBE

MTBE was once the top choice to boost octane and lower tail-pipe carbon monoxide. Soon, leaks from underground storage tanks showed that MTBE persists in water and gives it a strong turpentine-like odor. Many regions replaced MTBE with ethanol or other additives.

 

Questions for you:

1. Which structural feature of MTBE limits its biodegradation?

2. How does a compound’s solubility in water affect its spread in groundwater?

3. Suggest two alternative fuel oxygenates and compare their environmental profiles.

5.7 Try It Yourself – Practice Problems

1. Match each compound with the property that makes it suitable for its main use:

    

   a) Isopropanolb) Propylene glycolc) Tetrahydrofurand) Sevoflurane

    

   i. Safer pet antifreezeii. Stable yet volatile inhalation anestheticiii. Laboratory solvent for PVCiv. Rubbing alcohol for disinfecting skin

2. You are formulating a paint stripper. It must dissolve oil-based paints quickly but evaporate slowly enough to give working time. Which alcohol or ether would you test first and why? Consider polarity, boiling point, and safety.

3. Calculate the volume of ethanol needed to provide the same energy as 50 L of gasoline. Assume gasoline provides 34 MJ L⁻¹ and ethanol provides 24 MJ L⁻¹. Show your steps.

4. A laboratory bottle of diethyl ether has been stored for two years. Outline a step-by-step protocol to decide whether it is safe to open and how to dispose of it if not.

5.8 Discussion Prompts

1. Governments sometimes subsidize corn-based ethanol. List two benefits and two drawbacks of this policy from economic, environmental, and social viewpoints.

2. Inhalation anesthetics are potent greenhouse gases. Should hospitals be required to capture and recycle them? Debate possible costs versus climate benefits.

3. Compare the risk–benefit profiles of ethanol in beverages and in hand sanitizers. Where should regulatory agencies place stricter controls?

5.9 Key Takeaways

• The practical uses of alcohols and ethers arise directly from their structures: hydrogen bonding for solubility and boiling point in alcohols, and relative inertness and volatility in ethers.

• Ethanol leads the way as a disinfectant, solvent, flavor carrier, and renewable fuel, while specialized ethers excel as solvents, anesthetics, and fuel additives.

• Safety is central: flammability, toxicity, and environmental persistence all demand careful storage, handling, and disposal.

• Economic and social impacts range from job creation to better health care, but each benefit must be weighed against energy costs, pollution, and resource use.

• By linking chemistry to real-world concerns, you deepen your understanding and become prepared to make informed choices in laboratories, industry, and daily life.