Carbon and its Compounds · Lesson 10 of 13
Some Important Carbon Compounds – Ethanol
“Ethanol is a solvent, fuel and reaction partner with more chemistry than its familiar name suggests.”
• Describe important physical properties and uses of ethanol. • Explain the reaction of ethanol with sodium. • Explain dehydration of ethanol to ethene. • Explain the role of concentrated sulphuric acid as a dehydrating agent. • Distinguish ethanol, methanol and denatured alcohol using the information given in the chapter.
Ethanol is one of the most familiar carbon compounds. It is a liquid, mixes with water in all proportions and is an important solvent. Its reactions also connect functional groups with the hydrocarbon chemistry studied earlier.
Properties Of Ethanol
Ethanol is a liquid at room temperature and is commonly called alcohol. It is soluble in water in all proportions. Because it is a good solvent, it is used in preparations such as tincture iodine, cough syrups and tonics.
Reaction With Sodium
Ethanol reacts with sodium metal and releases hydrogen gas. The other product is sodium ethoxide.
Problem
What observations and products should be expected when sodium reacts with ethanol?
- 1.Sodium reacts with the alcohol functional group.
- 2.Hydrogen gas is evolved and can be identified by its characteristic ignition test.
- 3.The organic product is sodium ethoxide.
- 4.The balanced equation uses two sodium atoms and two ethanol molecules to produce one hydrogen molecule.
Reaction To Give Unsaturated Hydrocarbon
When ethanol is heated with excess concentrated sulphuric acid, water is removed from ethanol and ethene is formed. This is a dehydration reaction.
A Dehydrating Agent removes water from another substance during a reaction.
Concentrated sulphuric acid acts as the dehydrating agent. Notice the structural change: ethanol contains only single carbon-carbon bonding, while ethene contains a C=C double bond and is unsaturated.
Alcohol As A Fuel
Sugarcane juice can be processed into molasses and fermented to produce ethanol. Ethanol can be used as a fuel or blended with petrol. When burned completely in sufficient oxygen, it forms carbon dioxide and water.
How Alcohols Affect Living Beings
The chapter describes ethanol as affecting the central nervous system when consumed in large amounts. It can slow metabolic processes and impair coordination, judgement and timing.
Methanol
Methanol is much more dangerous. Even small amounts can be fatal. The chapter explains that methanol can be oxidised in the liver to methanal, which damages cells and can affect the optic nerve, causing blindness.
Denatured Alcohol
Denatured Alcohol is industrial ethanol made unfit for drinking by adding poisonous substances and often colouring agents.
Industrial ethanol may be mixed with substances such as methanol and coloured so it can be identified easily and cannot be misused as a beverage.
| Substance | Key Point |
|---|---|
| Ethanol | Useful solvent and fuel; mixes with water |
| Methanol | Highly toxic even in small amounts |
| Denatured alcohol | Industrial ethanol deliberately made unfit for drinking |
Quiz
What gas is evolved when ethanol reacts with sodium?
What is the product formed with sodium besides hydrogen?
What is formed when ethanol is dehydrated?
What role does concentrated sulphuric acid play in ethanol dehydration?
What is denatured alcohol?
Practice Problems
- Describe the physical properties and uses of ethanol given in the chapter.
- Write and balance the reaction of ethanol with sodium and identify the gas evolved.
- Explain the dehydration of ethanol to ethene, including the role of concentrated sulphuric acid.
- Compare ethanol and ethene before and after dehydration in terms of bonding.
- Explain why ethanol can be used as a fuel.
- Distinguish ethanol, methanol and denatured alcohol using the information given in the chapter.
Key Takeaways
• Ethanol is a water-miscible liquid and a useful solvent. • Ethanol reacts with sodium to form sodium ethoxide and hydrogen. • Heating ethanol with concentrated sulphuric acid removes water and forms ethene. • Concentrated sulphuric acid acts as a dehydrating agent in this reaction. • Methanol is highly toxic, while denatured alcohol is industrial ethanol deliberately made unfit for drinking.