≫3.3 - Alcohols ✔

Question 1

What is the general formula of alcohols?

Answer 1

• CₙH₂ₙ₊₁OH

Question 2

What is the functional group of alcohols?

Answer 2

• R-OH

Question 3

What is the classification of alcohols?

Answer 3

• Alcohols can either by primary (1°), secondary (2°) or tertiary (3°).

Question 4

Why is the boiling point of alcohols relatively high?

Answer 4

• Because of the hydrogen bonding between molecules.

Question 5

Sketch a diagram of the hydrogen bonding between methanol and water:

Answer 5

Question 6

Alcohol Production:

Besides hydration and fermentation what two ways can alcohols be produced by?

(name the reagent and conditions)

Answer 6

• Nucleophilic substitution of a halogenoalkane:
  -Reagent: NaOH or KOH.
  -Conditions: reflux, dissolve halogenoalkane in a little ethanol, aqueous reagent.
• Electrophilic addition of an alkene with concentrated sulphuric acid followed by the reaction with water applying heat.

Question 7

Alcohol Production:

Outline the mechanism name, equation, conditions and draw the mechanism for hydration of alkenes:

(C₂H₄)

Answer 7

Industrial Method:

• Electrophilic addition.
• C₂H₄ + H₂O ⇌ C₂H₅OH
• Conditions: concentrated sulphuric acid, pressure of 60atms, temperature of 600K and excess ethene to give a high yield.

Question 8

What are uses of fermented alcohols?

Answer 8

• Wine/beer - alcoholic drinks (If the alcoholic drink needs a higher concentration of alcohol, then fractional distillation is needed.)
• Biofuels (Ethanol produced is separated via fractional distillation and then used as biofuel.)

Question 9

What is the meaning of the term biofuel?

Answer 9

• A fuel derived immediately from living matter.

Question 10

What does carbon-neutral mean?

Answer 10

• This is an activity in which there is no net annual emissions of CO₂ into the atmosphere.

Question 11

Reactions of Alcohols - Elimination of alcohols:

What are the conditions, the overall equation and outline the mechanism:

(Starting reagent: C₂H₅OH)

Answer 11

• Concentrated sulphuric acid (H₂SO₄) at 170°C acting as a catalyst providing H+ ion.
• C₂H₅OH → C₂H₄ + H₂O

Question 12

Reactions of Alcohols - Combustion of alcohols:

Give the complete combustion equation for ethanol and the incomplete combustion equation for pentanol:

Answer 12

• C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O
• C₅H₁₁OH + 5O₂ → 5CO + 6H₂O