3.3.5 Alcohols Knowledge Flashcards
what is an alcohol?
molecule with a hydroxyl functional group attached to a hydrocarbon chain
what is the general formula of alcohols?
CnH2n+1OH
what is the functional group isomer of butan-1-ol?
ethoxyethane - H3CCHOCHCH3
what is the carbonyl group?
C=O
what is the carbonyl group bonded to in aldehydes?
Carbonyl bonded to at least one H atom
what is the structural formula for the carbonyl group in an aldehyde?
CHO
what is the suffix for an aldehyde?
-al
what number is the carbonyl group in an aldehyde?
The carbonyl group in an aldehyde is always C number 1
what is the carbonyl group bonded to in ketones?
Carbonyl bonded to two C atoms
what is the structural formula for the carbonyl group in a ketone?
CO
what is the suffix for a ketone?
-one
what number is the carbonyl group in a ketone?
Because the C= can be at different positions in a chain, they often require a number that is not 1
what is the carbonyl group bonded to in carboxylic acids?
Carbonyl bonded to an OH group
what is the structural formula for the carbonyl group in a carboxylic acid?
COOH
what is the suffix for a carboxylic acid?
-oic acid
what number is the carbonyl group in a carboxylic acid?
The carbonyl in carboxylic acids is always C number 1
How many [o]s are used in the oxidation of a primary alcohol through distillation?
1
How many [o]s are used in the oxidation of an aldehyde through reflux?
1
How many [o]s are used in the oxidation of a primary alcohol through reflux?
2
How many [o]s are used in the oxidation of a secondary alcohol?
1
How many waters are produced in the oxidation of a primary alcohol under distillation?
1
How many waters are produced in the oxidation of an aldehyde under reflux
0
How many waters are produced in the oxidation of a primary alcohol under reflux.
1
How many waters are produced in the oxidation of a secondary alcohol?
1
What is the oxidising agent for the the oxidation of alcohols?
Acidified potassium dichromate
What is the observation for alcohol oxidation?
Orange (Cr2O7^2-) to green (Cr3+)
How do you test for types of alcohols?
- Test that you have an alcohol by testing for the -OH group; show that it is a neutral liquid, free of water and that it reacted with solid phosphorus(V) chloride to produce a burst of acidic steamy hydrogen chloride fumes.
- Add a few drops of the alcohol to a test tube containing potassium dichromate(VI) solution acidified with dilute sulphuric acid.
- Warm tube would be in a hot water bath.
- In the case of a primary or secondary alcohol, the orange solution turns green. With a tertiary alcohol there is no colour change.
- Produce enough of the aldehyde (from oxidation of a primary alcohol) or ketone (from a secondary alcohol) to be able to test them. There are various things which aldehydes do which ketones don’t. These include the reactions with Tollens’ reagent, Fehling’s solution and Benedict’s solution
Why don’t tertiary alcohols oxidise?
- With primary and secondary alcohols, the oxidising agent removes the hydrogen from the -OH group, and a hydrogen from the carbon atom attached to the -OH. Tertiary alcohols don’t have a hydrogen atom attached to that carbon.
- You need to be able to remove those two particular hydrogen atoms in order to set up the carbon-oxygen double bond.
what is the reagent for turning a primary alcohol into an aldehyde?
acidified potassium dichromate
what conditions are required for turning a primary alcohol into an aldehye?
Heat under distillation
what does a primary alcohol become when it is heated under distillation with acidified potassium dichromate?
aldehyde
what is the reagent for turning an aldehyde into a carboxylic acid?
acidified potassium dichromate
what conditions are required to turn an aldehyde into a carboxylic acid?
heat under reflux
what does an aldehyde become when it is heated under reflux with acidified potassium dichromate?
carboxylic acid
what is the reagent for turning a primary alcohol into a carboxylic acid?
acidified potassium dichromate
what conditions are required to turn a primary alcohol into a carboxylic acid?
heat under reflux, excess oxidising agent
what does a primary alcohol become when it is heated under reflux with excess acidified potassium discorhomae?
carboxylic acid
what is the reagent for turning a secondary alcohol into a ketone?
acidified potassium dichromate
what conditions are required to turn a secondary alcohol into a ketone?
heat under reflux or distillation
what does a secondary alcohol become when it is heated with acidified potassium dichromate?
ketone
why does the choice of heat under reflux or distillation affect what is produced from the oxidation of a primary alcohol?
because of the different boiling points of alcohols, aldehydes, and carboxylic acids
what is the strongest IMF in alcohols?
hydrogen bonding
what is the strongest IMF in carboxylic acids?
hydrogen bonding
what is the strongest IMF in aldehydes?
p.d.d
which out of alcohols, aldehydes, and carboxylic acids have the lowest boiling point and why?
- The strongest IMF in alcohols is hydrogen bonding
- The strongest IMF in carboxylic acids is hydrogen bonding
- The strongest IMF in aldehydes is p.d.d; this is the weakest IMF so has the lowest boiling point
describe the structure and function of a condenser
- Are open at both ends
- Cold water flows around the outside
- Cools hot vapour and condenses it to a liquid
what is the purpose of anti-bumping granules?
- Heating of a reaction mixture can cause the formation of large bubbles and ‘bumping’ of the equipment, which is unsafe
- Anti-Bumping Granules added to the reaction mixture prevent the formation of large bubbles
why is Reflux is used to oxidise a primary alcohol to a carboxylic acid?
as it doesn’t allow any reactant vapour to escape
describe the production of ethanoic acid from ethanol useing reflux apparatus
- Ethanol and acidified K2Cr2O7 are heated to boiling point for a prolonged time.
- Ethanal vapour is formed which escapes from the liquid mixture
- Ethanal vapour is then condensed back into liquid and returns to the reaction mixture.
- Any ethanal and ethanol that initially evaporates can then be oxidised.
describe the process of creating a carboxylic acid from a primary alcohol using reflux apparatus?
- Aldehyde vapour rises and enters condenser
- Aldehyde vapour cools and condenses, then drops back into reaction mixture
why do condensers have an open top/end?
to prevent pressure build up, which could cause an explosion
where should the thermometer be in distillation apparatus?
The thermometer must be level with the side arm
why is distillation used to produce aldehydes from primary alcohols?
As the aldehyde is produced in distillation, it forms a vapour and escapes from the reaction mixture into the condenser. Distillation allows the aldehyde to escape the reaction mixture and prevents further oxidation.
describe how aldehydes are produced from primary alcohols under distillation
- Aldehyde vapour rises and enters condenser
- Aldehyde vapour cools and condenses
- Aldehyde product is collected
