Alcohols Flashcards
What is the functional group of an alcohol?
-OH
How should you name alcohols?
alkan-?-ol
What are 2 uses of ethanol and methanol? (of interest only)
Ethanol:
1 - In alcoholic drinks
2 - As a solvent (e.g. in methylated spirits)
Methanol:
1 - Petrol additive (to improve combustion)
2 - Chemical feedstock to make organic products
Name the 2 ways it is possible to make ethanol
1 - Hydration of ethene
2 - Fermentation of sugars
What are the reagents used in hydration of ethene?
H20 (g)/steam
use alcohols booklet to see equation of hydration of ethene in displayed formula
What are the conditions of hydration of ethene
- Phosphoric acid (H3PO4) catalyst
- High temperature
- High pressure
What is the use of ethanol when made from hydration of ethene?
As a solvent and a chemical feedstock
What is the atom economy of hydration of ethene? How do you know?
100% atom economy
This is because in the reaction there is only 1 product made and it is useful so 100% of the atoms in the reactants are reacted into the useful product
What is the yield of ethanol when made from hydration of ethene?
100% yield (eventually)
Where does ethene come from?
Catalytic cracking of crude oil
What is the reagent in fermentation of sugars?
Glucose, C6H12O6
What must the conditions of fermentation of sugars be?
- Enzyme (in yeast)
- 37 degrees
What is the use of ethanol produced from the fermentation of sugars?
in alcoholic drinks
What observations can be made from the fermentation of sugars?
Bubbles of gas (from the carbon dioxide produced)
What is the atom economy of fermentation of sugars?
51%
What is the yield of ethanol from fermentation of sugars?
7-14%
How does the solubility of alcohols change when chain length is increased? Why?
Solubility decreases as the chain length increases because:
- A larger part of the molecule is made up of a non-polar hydrocarbon chain
- The hydrocarbon chain does not form hydrogen bonds with water molecules
Get a piece of paper and show an illustration of hydrogen bonding between water and ethanol
Check answer on pg 3 of alcohols booklet
How does the boiling point of an alcohol and an alkane differ? Why is this?
Alcohols have higher boiling points than alkanes (of similar Mr)
This is because a significant amount of heat energy is needed to overcome the hydrogen bonds in alcohols whereas the intermolecular forces in alkanes are London forces - alcohols have a lower volatility than alkanes
What is a primary alcohol?
The -OH group is attached to a carbon with only one alkyl group
What is a secondary alcohol?
The -OH group is attached to a carbon with two alkyl groups
What is a tertiary alcohol?
The -OH group is attached to a carbon with three alkyl groups
What are the reagents in the elimination of H20 from an alcohol?
Concentrated phosphoric acid/sulfuric acid (+ alcohol)
What is a dehydration reaction?
A H2O molecule is removed from a saturated molecule (alcohol) to form an unsaturated molecule (alkene)
What types of alcohols can be oxidised using an oxidising agent?
Primary and secondary alcohols
Which type of alcohol cannot be oxidised?
Tertiary alcohols
What is a suitable oxidising agent for alcohols?
Acidified dichromate Cr2O72-/H+
What is the symbol for the oxidising agent in an equation?
[O]
During the reaction, what colour does the oxidising agent change from?
From orange to green
What does partial oxidation of a primary alcohol produce?
Aldehydes
What conditions must there be to undergo partial oxidation?
Heat by distillation
Why can you not heat under reflux to make an aldehyde?
If possible then heating under reflux will make a carboxylic acid
What does further/complete oxidation of a primary alcohol produce?
Carboxylic acids
What does the oxidation of secondary alcohols produce?
Ketones
What can’t ketones be oxidised?
The carbon attached to the ketone functional group had no hydrogen bonded (to the C=O carbon) so cannot be oxidised
Why can’t a tertiary alcohol be oxidised?
Doesn’t have a H atom on the C to which the OH is attached
What do alcohols react with to form haloalkanes?
Hydrogen halides
What condition is needed to make an alcohol into a haloalkane?
Heat under reflux
What reagents are needed to make an alcohol into a haloalkane?
Metal halide and concentrated sulfuric acid (to make hydrogen halide) + alcohol
