Module 4: Chapter 14 Alcohols Flashcards Preview

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Flashcards in Module 4: Chapter 14 Alcohols Deck (16)
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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)


Describe substitution reaction of alcohols?

a reaction in which one atom or group (-OH) is replaced by another atom or group (-Br)
- forms water