Module 4: Chapter 14 Alcohols Flashcards
What are alcohols?
- the -OH group attached to carbon atoms is called the hydroxyl group
- an alcohol has a hydroxyl group attached to carbon chain or alicyclic ring
- a hydroxyl attached to an aromatic ring is called a phenol and is different in its reaction to alcohols
How do you name alcohols/
(alkyl groups) longest carbon chain name (minus ‘e’ unless there’s more than one -OH) - position of alcohol group(s) - (di/tri/tetra) ol
What is a primary alcohol?
the OH carbon joined to one other carbon or has 2 hydrogen atoms on it
What is a secondary alcohol?
the OH carbon is only directly joined to 2 other carbons or has 1 hydrogen atom attached to it
What is tertiary alcohol?
the OH carbon is directly joined to 3 other carbons or has no hydrogen atoms attached
What are the intermolecular forces of alcohols?
- alcohols are polar molecules
- alcohol molecules can form hydrogen bonds with each other
- allows for alcohols to mix with water and gives alcohols much higher boiling points
What happens to intermolecular forces when the chain gets longer?
- as the carbon chain gets longer the strength of London forces become more important and stronger
- in all cases more energy is needed to overcome the additional hydrogen bondings in alcohols compared to corresponding alkane
- as the carbon chain gets longer the solubility in water falls. H2O forms stronger attractions to other H2O’s than it can form to non-polar carbon chains
What are the uses of alcohols?
- Methanol can be used as a fuel, combusts efficiently and exists as a liquid at room temperature
· however is toxic and engine corrosive
· methanol is a feedstock for making polymers, paints and glues - Ethanol is the alcohol in drinks, it’s also used as a fuels (sometimes mixed with petrol), solvent and feedstock
- Ethane-1,2-diol is used as antifreeze
Describe the combustion of alcohols?
- exothermic reaction
- complete combustion
Describe the oxidation of alcohols?
- the hydroxyl group of some alcohols can be oxidised using potassium dichromate (VI) solution (K2Cr2O7) acidified with dilute sulfuric acid (H2SO4)
- orange to green as dichromate ions are reduced into chromium ions
- oxidising agent represented by [O]
- H2O is also a product
What are the organic products of oxidation of alcohols?
Primary alcohols:
- aldehyde -COH (gentle heating with distillation) + H2O
- carboxylic acid -COOH (high temperature under reflux, excess acidified K2Cr2O7)
Secondary alcohols:
- ketone (reflux) -C=O
Tertiary alcohols:
- not oxidised as tertiary alcohols don’t have a hydrogen atom bonded to the carbon atom carrying the -OH group
What is reflux?
- a process that allows continuous heating of volatile reactants (vertical condenser)
- vaporised reactants condense and drip back into the reaction vessel to continue reaction
What is distillation?
Uses a side mounted condenser to separate liquids according to their boiling points
Describe the dehydration of alcohols (eliminations reaction)?
- dehydration reaction is when a water molecule is removed from the the starting material
- heat alcohol under reflux in the presence of an acid catalyst (concentrated H2SO4/H3PO4)
- forms an alkene and water
What is an elimination reaction?
An elimination reaction is a reaction in which a small molecule is removed from a larger molecule leaving an unsaturated molecule (reverse addition reactions)
