2.7 alcohols and carboxylic acids

what is the general formula for alcohols?

CnH2n+1OH

What are the conditions for the industrial production of ethanol from ethene?

Hydration of ethene:
- phosphoric acid catalyst (aqueous)
- temperature of 300 degrees and high pressure (60/70atm)

what is the chemical equation for the hydration of ethene?

CH2CH2 + H20 = CH3CH2OH

How can ethanol be produced from a renewable source?

ethanol can be produced from the fermentation of sugars. In crops, enzymes break down starch into sugars which can then undergo fermentation to form ethanol

what conditions are required for the fermentation of glucose to form ethanol?

- carried out with yeast
- 30-40 degrees temperature
- anaerobic conditions (no oxygen)

what is the chemical equation for the fermentation of glucose to form ethanol?

C6H1206 = 2C2H5OH + 2CO2

After fermentation, how can ethanol be separated from the rest of the reaction mixture?

distillation

what is formed when alcohols undergo dehydration?

alkenes

why is the production of ethanol fuel from glucose said to be carbon neutral?

a process is carbon neutral if it contributes no net increase to the amount of carbon dioxide in the atmosphere

ethanol fuel, produced from glucose is carbon neutral because the crops take in carbon dioxide during photosynthesis which balances out the amount of carbon dioxide that is released when the fuel is burned

how do alcohols undergo dehydration reactions?

alcohols undergo dehydration reactions to form an alkene and a water molecule

two ways to carry out dehydration
- heat with strong acid catalyst
- pass alcohol vapour over AL2O3 powder

explain the classification of primary alcohols?

the OH is joined to a carbon atom that has 1 R group and 2 h atoms

explain the classification of secondary alcohols?

The OH is joined to a carbon atom that has 2 R groups and 1H atom

explain the classification of tertiary alcohols?

the OH is joined to a carbon atom that has 3R groups and O H atoms

how are primary alcohols oxidised to aldehydes?

if a primary alcohol is heated under reflux with acidified potassium dichromate VI, the alcohol will be oxidised form a carboxylic acid.

the acidified potassium dichromate VI will change colour from orange to green

how are secondary alcohols oxidised to ketones?

if a secondary alcohol is heated under reflux with acidified potassium dichromate VI, the alcohol will be oxidised to form a ketone

the acidified potassium dichromate VI will change colour from orange to green

what test can be carried out to test alcohol?

add acidified potassium dichromate VI

the acidified potassium dichromate VI will change colour from orange to green

what test can be carried out for carboxylic acids?

add sodium hydrogen carbonate (NaHCO3)

The solution will bubble and the carbon dioxide will be produced if a carboxylic acid is present. The gas released can be tested with limewater to identify it as carbon dioxide

what is produced when carboxylic acids react with bases?

salt and water

what is produced when carboxylic acids react with carbonates?

salt, carbon dioxide and water

what is produced when carboxylic acids react with hydrogencarbonates?

salt, carbon dioxide and water

how do alcohols react with carboxylic acids?

alcohols react with carboxylic acids to form esters. this process is called esterification and requires heating with a sulfuric acid catalyst

explain how ethanol can be separated from water

ethanol and water have different boiling points so they can be separated by distillation;
- the mixture is heated until the ethanol evaporates
- the ethanol vapours enter the condenser where they condense and run into a beaker

two methods that ethene are used

- hydration of ethene
- fermentation of sugars

how is ethene formed?

ethene comes from the cracking of hydrocarbons produced from petrol

what is the equation of combustion of ethene

C2H5OH + O2 = 2CO2 + 3H20

what are the advantages of fossils fuels?

- renewable
- greenhouses gases

what are the disadvantages of fossils fuels?

- land use
- use of resources
- carbon neutrality

suggest why would need fractional distillation rather than simple distillation to separate the ethanol from the mixture?

The boiling temp are similar can both evaporate and heating the fractionating column allows the water to condense before column allows the water to condense before reaching the top

method on partial oxidation?

heat gently with a small amount of oxidising reagent and add distil to form aldehyde

method on complete oxidation?

heat strongly under reflux with a small volume of alcohol and excess oxidation reagent