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63 Cards in this Set
- Front
- Back
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What is the functional group in alcohols? |
OH also known as the hydroxyl group. It's responsible for the chemical and physical properties of the alcohols. |
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How do you name alcohols? |
You use the suffix -ol. The position of the OH group is given to the lowest number possible on the carbon backbone. |
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What are the uses of ethanol? |
In alcoholic drinks As a solvent (e.g. methylated spirits) |
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What are the uses of methanol? |
As a petrol additive (to improve combustion) As a chemical feedstock to make organic compounds. |
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What are the 2 ways you can make ethanol? |
The hydration of ethene Fermentation of sugars |
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What are the reagents in the hydration of ethene? |
H2O(g) (steam) and ethene |
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What conditions are required for the hydration of ethene? |
A phosphoric acid catalyst, high temperatures and high pressures. |
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What is the formula for phosphoric acid? |
H3PO4 |
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What is the ethanol produced by this method usually used for? |
As a solvent and a chemical feedstock |
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What reagent is required to produce ethanol from the fermentation of sugars? |
Glucose |
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What conditions are required? |
Enzyme (in yeast) and 37 degrees c. No oxygen as respiration is anaerobic |
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What is ethanol produced by this method usually used for? |
Alcoholic drinks |
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What is the atom economy and yield of ethanol from the hydration of ethene? |
100% atom economy as it's an addition reaction. 100% yield. |
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What is the source of the reactants for the hydration of ethene? |
Ethene is obtained from the catalytic cracking of crude oil. Crude oil is non-renewable as it takes millions of years to form. |
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What is the atom economy and yield of ethanol produced by fermentation? |
Atom economy is less than 100% as two products are formed from one reactant.
Yield is 7-14 % |
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What is the source of the reactants in fermentation? |
The source of glucose is sugar cane. It's renewable as sugar cane can be regrown. It makes bioethanol. |
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Can alcohols dissolve in water |
Alcohols dissolve in water because the polar OH group forms hydrogen bonds with polar H2O molecules. |
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Which alcohols are soluble? |
The first three in the alcohol homologous series are soluble in water. |
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What happens as you add CH2 to the alcohol? |
Solubility decreases as the chain length increases. |
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Why does solubility decrease as chain length increases? |
A larger part of the alcohol molecule is made up of a non-polar hydrocarbon chain. The hydrocarbon chain doesn't form hydrogen bonds with water molecules. |
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Are alkanes soluble in water? |
No because they're comprised of non-polar molecules which can't hydrogen bonds with water molecules. |
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What is the boiling point of alcohols like? |
They have higher boiling points than alkanes of a similar Mr. |
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Why is this? |
Hydrogen bonds form between alcohol molecules, so a significant amount of energy is required to break them in order to turn them from the liquid state into a vapour. This requires more energy than overcoming the weak London forces in alkanes. |
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What is another result of this? |
Alcohols have a lower volatility than alkanes with the same number of carbon atoms. |
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How are alcohols classified? |
They can be classified into primary, secondary and tertiary alcohols based on the number of alkyl groups. |
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What is a primary alcohol? |
An alcohol where the OH group is attached to a carbon with only one alkyl group. |
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What is a secondary alcohol? |
An alcohol where the OH group is attached to a carbon with 2 alkyl groups.
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What is a tertiary alcohol? |
An alcohol where the OH group is attached to a carbon with 3 alkyl groups.
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What reactions can alcohols be involved in? |
Combustion The elimination of H2O from an alcohol Oxidation of primary and secondary alcohols Nucleophilic substitution |
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What happens in combustion of alcohols? |
In a plentiful supply oxygen, they burn to give CO2 and H20. |
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What reagents are required for the elimination of H2O from an alcohol? |
A concentrated H3PO4(phosphoric acid) or H2SO4 (sulphuric acid) catalyst and alcohol. |
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What conditions are required for the elimination of H2O form an alcohol? |
Heating under reflux |
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What is the elimination of H2O from an alcohol also known as? |
The dehydration of an alcohol |
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What is dehydration? |
A reaction where a H2O molecule is removed from a saturated molecule to form an unsaturated molecule. |
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Which types of alcohols can be oxidised? |
Primary and secondary alcohols can be oxidised using an oxidising agent. |
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Which alcohols can't be oxidised? |
Tertiary alcohols |
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What is a suitable oxidising agent? |
A solution containing acidified dichromate |
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What is the symbol for an oxidising agent in a balanced chemical equation? |
[O] |
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What happens during the reaction? |
The oxidising agent changes colour from orange to green |
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What reagents are required for the oxidation of a primary alcohols? |
Acidified dichromate (H2SO4 and Na2Cr2O7) |
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What conditions are required for the oxidation of primary alcohols? |
Heating by distillation |
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What products are formed by the partial oxidation of a primary alcohol? |
An aldehyde and water |
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How is a primary alcohol oxidised? |
The primary alcohol is heated under distillation so that the aldehyde is separated from the mixture and to prevent further oxidation to the carboxylic acid.
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What method is used to partially oxidise a primary alcohol? |
Acidified dichromate solution is added to the top gradually via a tap funnel. It travels down the vertical condenser to the alcohol. It then returns to the top where it collects it a flask at the bottom. This solution that collects has partially oxidised the alcohol. Water is run along the apparatus and the aldehyde collects at the bottom. This process is called continuous distillation.
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What can the oxidising agent then do? |
It can further oxidise the aldehyde to produce a carboxylic acid. Here, it gains one oxygen atom. |
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How is a primary alcohol completely oxidised? |
It's heated under reflux |
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What products does this give? |
A carboxylic acid and water. Water is lost and oxygen is gained |
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What reagents are required for the oxidation of secondary alcohols? |
Acidified dichromate (H2SO4 and K2Cr2O7) |
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What conditions are required for the oxidation of secondary alcohols? |
Heating under reflux |
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What are the products of the oxidation of secondary alcohols? |
A ketone and water |
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Why can tertiary alcohols not be oxidised? |
They don't have a H atom on the carbon which the OH is attached to. |
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What happens in nucleophilic substitution with alcohols? |
Alcohols react with halogens to form haloalkanes. |
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What reagents are required for this? |
A NaBr and concentrated H2SO4 |
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What conditions are required? |
Heating under reflux |
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What happens when heating under reflux? |
The alcohol is heated with sulfuric acid and a sodium halide. This forms a hydrogen halide in situ. |
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What does this mean? |
The reagents to make the hydrogen halide are mixed with the alcohol. |
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What is the first part of the reaction if the sodium halide is sodium bromide? |
H2SO4 (aq) + NaBr(s) -->NaHSO4(aq) + HBr(aq) |
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What is the equation when the alcohol is added (ethanol)? |
C2H6O + HBr --> C2H5Br + H2O |
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What is the overall equation for the reaction of ethanol with sulfuric acid and sodium bromide? |
CH3CH2OH + NaBr + H2SO4 --> CH3CH2Br + NaHSO4 + H2O |
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What do you change if there's more then one OH group? |
Don't drop the e from the name |
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What type of process is fermentation to produce ethanol and why? |
It's a batch process as the CO2 the bacteria produces in respiration makes the solution acidic. This denatures the enzyme so it must be replaced |
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What type of process is hydration of ethene? |
Continuous |
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What must you remember when balancing a combustion of alcohol reaction? |
The O in the OH group |
