4.2.1 Alcohols Flashcards
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.
- CH₃CHOHCH₃ (l) + [O] -> CH₃COCH₃ (g) + H₂O (l)
Is it possible to oxidise a tertiary alcohol?
- No
What is a dehydration reaction?
- A reaction where water is lost to form an organic compound
What are the products of a 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 a 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
