[Year 1] WM Flashcards
How do you identify an alcohol?
R-OH
Suffix: -ol
ethanol, CH₃CH₂OH
How do you identify an aldehyde?
R-COH
Suffix: -al
propanal, CH₃CH₂CHO
How do you identify a ketone?
R-CO-R’
-one
propanone, CH₃COCH₃
How do you identify a carboxylic acid?
R-COOH
Suffix: -oic acid
butanoic acid, CH₃CH₂CH₂COOH
How do you identify an acid anhydrides?
(R-CO)₂O
-oic anhydride
ethanoic anhydride, (CH₃CO)₂
How do you identify an ether?
R-O-R’
-oxy-
methoxyethane, CH₃OCH₂CH₃
How do you identify an ester?
R-COO-R’
alkyl-____-anoate
methyl ethanoate, CH₃COOCH₃
What makes an alcohol primary?
If the carbon it is connected to, is connected to one other carbon.
What makes an alcohol secondary?
If the carbon it is connected to, is connected to two other carbons.
What makes an alcohol tertiary?
If the carbon it is connected to, is connected to three other carbons.
What happens when you oxidise primary alcohol?
Becomes an aldehyde (distillation) then carboxylic acid (reflux with excess oxidising agent).
What happens when you oxidise secondary alcohol?
Becomes a ketone (reflux).
What happens when you oxidise tertiary alcohol?
Cant be oxidised (unless you burn it).
What is used to oxides alcohols?
Acidified potassium dichromate (K₂Cr₂O₇).
- acts as the oxidising agent, so it reduces itself.
- Turn from orange (dichromate ions) to green (chromium ions).
What are you doing when you distil something?
You are removing the desired product as it is formed.
What are you doing when you reflux something?
Heating reactants and condensing any volatile products/reactants to carry on the reaction.
What type of reaction forms alkenes from alcohols?
An elimination reaction.
- By refluxing with sulfuric acid or phosphoric acid.
- By passing alcohol vapour over a solid catalyst (Al₂O₃). (need to be able to draw this).
Describe the mechanism to dehydrate alcohols using elimination.
- Lone pair on Oxygen attack H⁺ from the acid catalyst.
- The intermediate formed has a + charge on the oxygen.
- This oxygen can pull electrons in the C-O bond strongly to break the bond.
- This leaves an unstable carbocation intermediate. (water leaves)
- The carbocation loses a H⁺ from a neighbouring carbon to form a C=C bond as the electrons from the bond move.
- This leaves an alkene, water, and reforms the H⁺ from the acid catalyst.
How can esters be made from alcohols?
Reacting them with a carboxylic acid:
- using a sulfuric acid catalyst.
- -OH from carboxylic acid is removed.
- -OR from alohol bond in its place.
- The removed -OH bonds with -H from alcohol.
Or acid anhydride:
- A C-O bond in the acid anhydride is broken.
- -R from the alcohol takes its place.
- the remaining -OH in the alcohol bonds with the smaller fragment to form a carboxylic acid.
Know how to draw these.
How can haloalkanes be made from alcohols?
Via a substitution reaction (e.g. HBr).
- -OH replaced by -Br.
- -OH forms water with remaining -H.
What is phenol and how are they numbered?
- A benzene ring with an alcohol group.
- carbon with the alcohol is the 1-carbon.
How do you test for phenols?
Add iron(III) chloride.
If phenol exists a purple colour should form.
Why can phenols react with NaOH?
- They are weak acids as they are able to dissociate partially to form a phenoxide ion.
- This phenoxide ion can then bond to Na⁺.
(an react with other strong bases too)
How can you tell the difference between phenols and carboxylic acids?
Carboxylic acids can react with weak bases whilst phenols cannot.
So you react carbonates with them to identify.