4.2.1 Alcohols: Module 4: Core Organic Chemistry: Chemistry OCR A A Level

What is the functional group of an alcohol?

Hydroxyl group -OH

What is the general formula of an alcohol?

CnH2n+1OH

How do you name alcohols (one prefix, one suffix)?

Hydroxyl- OR -ol.

What kind of intermolecular forces do alcohols have? Why?

Hydrogen bonding, due to the electronegativity difference in the OH bond.

How do alcohols’ melting point and boiling point compare to other hydrocarbons’ of similar C chain lengths? Why?

Higher, because they have hydrogen bonding (strongest type of intermolecular force) → stronger than London forces.

Are alcohols soluble in water? Why does solubility depend on chain length?

Soluble when short chain - OH hydrogen bonds to hydrogen bond in water.

Insoluble when long chain - non-polarity of C-H bond takes precedence.

What makes an alcohol primary?

C bonded to OH is only bonded to one other C atom.

What makes an alcohol secondary?

C bonded to OH is bonded to two other C atoms.

What makes an alcohol tertiary?

C bonded to OH is bonded to three other C atoms.

Write an equation for the combustion of ethanol.

C2H5OH (l) + 3O2 (g) → 2CO2 (g) + 3H2O (l)

What forms if you partially oxidise a primary alcohol?

An aldehyde.

What conditions are needed to partially oxidise a primary alcohol?

Dilute sulphuric acid, potassium dichromate (VI), distill product as it’s produced, gentle heating.

Write an equation for the partial oxidation of ethanol.

CH3CH2OH (l) + [O] → CH3CHO (g) + H2O (l)

What forms if you fully oxidise a primary alcohol?

A carboxylic acid.

What conditions are needed to fully oxidise a primary alcohol?

Concentrated sulphuric acid, potassium dichromate (VI), reflux, strong heating.

Write an equation for the full oxidation of ethanol.

CH3CH2OH (l) + 2[O] → CH3COOH (g) + H2O (l)

What forms if you oxidise a secondary alcohol?

A ketone.

What conditions are needed for the oxidation of a secondary alcohol?

Concentrated sulphuric acid, potassium dichromate (VI), strong heating.

Write an equation for the oxidation of propan-2-ol.

CH3CH(OH)CH3 (l) + [O] → CH3COCH3 (g) + H2O (l)

Is it possible to oxidise tertiary alcohol?

No.

What is a dehydration reaction?

A reaction where water is lost to form an organic compound.

What are the products of dehydration reaction of alcohol?

Alkene and water.

What are the conditions required for dehydration of alcohol?

Concentrated sulfuric acid or concentrated phosphoric acid and 170°C.

What are the products of the halide substitution reaction with alcohol?

Haloalkane and water.

In what form is the halide used in halide substitution reaction?

In the form of hydrogen halide, e.g HBr.

How is hydrogen halide made in situ? Give examples.

A salt is reacted with acid to form the hydrogen halide. E.g sodium bromide reacts with sulfuric acid to form HBr. When iodine is reacted phosphoric acid is used as sulfuric acid oxidises iodide ions into iodine.