C15 Alcohol Flashcards
(19 cards)
How is ethanol produced industrially from alkenes?
By hydration of alkenes using steam in the presence of a phosphoric acid catalyst.
How is ethanol produced by fermentation?
By the anaerobic respiration of glucose using yeast at ~30°C.
What are the conditions for fermentation of glucose to produce ethanol?
30–40°C, no oxygen (anaerobic), yeast as catalyst, aqueous conditions.
What is a biofuel?
A fuel produced from renewable biological resources (e.g. plants).
Write the balanced equation for fermentation of glucose.
C₆H₁₂O₆ → 2 C₂H₅OH + 2 CO₂
Why might ethanol not be considered a fully carbon-neutral fuel?
Because CO₂ emissions may arise from farming, transport, and processing.
Outline the mechanism for the hydration of alkenes to alcohols.
Electrophilic addition: 1. Protonation of alkene 2. Carbocation formation 3. Nucleophilic attack by water 4. Deprotonation
Name one environmental benefit of using ethanol as a fuel.
Reduces reliance on fossil fuels and lowers net CO₂ emissions.
What reagent is used to oxidise alcohols?
Acidified potassium dichromate (K₂Cr₂O₇/H⁺).
What do primary alcohols oxidise to?
First to aldehydes, then to carboxylic acids.
What do secondary alcohols oxidise to?
Ketones.
Can tertiary alcohols be oxidised easily?
No, they resist oxidation under normal conditions.
How can you ensure only aldehydes are produced from a primary alcohol?
Use distillation to remove the aldehyde as it forms.
How can you obtain a carboxylic acid from a primary alcohol?
Use reflux to allow further oxidation of the aldehyde.
How can you distinguish between an aldehyde and a ketone?
Use Fehling’s or Tollens’ reagent — aldehydes give positive results.
What is elimination in alcohols?
The removal of a water molecule to form an alkene.
What conditions are required for the elimination of water from alcohols?
Heat with concentrated sulfuric or phosphoric acid.
Outline the mechanism for alcohol elimination.
- Protonation of -OH group 2. Formation of a carbocation 3. Loss of a proton from adjacent carbon to form a double bond.
Why is elimination of alcohols useful industrially?
Produces alkenes that can be used in polymer manufacture without crude oil.
