4.2.1 Alcohols Flashcards
(16 cards)
What causes alcohols to be polar?
The O–H bond is polar due to the electronegativity difference between oxygen and hydrogen.
Why are alcohols soluble in water?
Alcohols form hydrogen bonds with water molecules due to the presence of the polar O–H group.
Why do alcohols have lower volatility than alkanes?
Alcohols have hydrogen bonding between molecules
How is a primary alcohol defined?
A primary alcohol has the –OH group attached to a carbon atom bonded to one other carbon atom.
How is a secondary alcohol defined?
A secondary alcohol has the –OH group attached to a carbon atom bonded to two other carbon atoms.
How is a tertiary alcohol defined?
A tertiary alcohol has the –OH group attached to a carbon atom bonded to three other carbon atoms.
What are the products of complete combustion of an alcohol?
Carbon dioxide and water.
What is observed when a primary alcohol is oxidised under controlled conditions?
An aldehyde is formed; the orange solution of K₂Cr₂O₇ turns green.
What conditions are used to form an aldehyde from a primary alcohol?
Distillation with acidified potassium dichromate (K₂Cr₂O₇/H₂SO₄).
What conditions are used to form a carboxylic acid from a primary alcohol?
Reflux with excess acidified potassium dichromate (K₂Cr₂O₇/H₂SO₄).
What is observed when a secondary alcohol is oxidised?
A ketone is formed; the orange solution of K₂Cr₂O₇ turns green.
Why can’t tertiary alcohols be oxidised?
Tertiary alcohols do not have a hydrogen atom attached to the carbon bearing the –OH group
What is the reagent and condition for dehydrating an alcohol?
Concentrated H₃PO₄ or H₂SO₄ and heat.
What is the product of elimination of water from an alcohol?
An alkene is formed.
What is the reagent needed to substitute a halide into an alcohol?
A sodium halide (e.g. NaBr) and concentrated H₂SO₄.
What is the product when an alcohol reacts with NaBr and H₂SO₄?
A haloalkane is formed via substitution.
