2.7 Alcohols and Carboxylic Acids Flashcards
what is the functional group for all alcohols?
-OH
what is the general formula of alcohol?
CnH2n+1OH
What are the conditions for the industrial production of ethanol from ethene?
Hydration of ethene:
- Phosphoric acid catalyst (aqueous)
- Temperature of 300oC and high pressure 60-70 atm
Write the chemical equation for the hydration of ethene
CH2CH2+ H2O → 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?
- sugars are converted into ethanol
-Carried out with yeast - 30-40oC temperature
- Anaerobic conditions (no oxygen)
What is the chemical equation for the fermentation of glucose to form ethanol?
C6H12O6 → 2C2H5OH + 2CO2
After fermentation, how can ethanol be
separated from the rest of the reaction
mixture?
distillation
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
Why might someone argue that the
production of ethanol fuel from glucose is
not carbon neutral?
Energy is required to power the machinery to make fertilizers for the crops and to harvest the crops, which releases carbon dioxide. Similarly, more carbon dioxide is released during the transportation of the ethanol.
What is formed when alcohols undergo
dehydration?
alkenes
How do alcohols undergo dehydration
reactions?
Alcohols undergo dehydration reactions to form an alkene and a water molecule.
There are two ways to carry out dehydration:
- Heat with strong acid catalyst.
- Pass alcohol vapour over Al2O3
powder.
What is the chemical equation for the dehydration of propan-2-ol to form prop-2-ene?
CH3CH(OH)CH3 → CH2CHCH3 + H2O
Explain the classification of alcohols
- Primary, 1° - The carbon bonded to the hydroxyl group is bonded to one R group only.
- Secondary, 2° - The carbon bonded to the hydroxyl group is bonded to two R groups.
- Tertiary, 3° - The carbon bonded to the hydroxyl group is bonded to three R groups.
How are primary alcohols oxidised to
aldehydes?
If you heat a primary alcohol with acidified potassium dichromate(VI), the alcohol will be oxidised to form an aldehyde:
CH3CH2OH + [O] → CH3CHO + H2O
The acidified potassium dichromate(VI) will change colour from orange to green
How are secondary alcohols oxidised to
ketones?
The acidified potassium dichromate(VI) will change colour
from orange to green.
What qualitative test can be carried out
to test for primary and secondary
alcohols?
Add acidified potassium dichromate(VI):
The solution will change colour from orange
to green if a primary or secondary alcohol is
present.
What qualitative test can be carried out to test for carboxylic acids?
Add sodium hydrogen carbonate (NaHCO3):
The solution will effervesce and 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 the chemical equation for the reaction of ethanoic acid with sodium hydroxide?
CH3COOH + NaOH → CH3COO-Na+ + H2O
What is produced when carboxylic acids
react with carbonates?
Salt, carbon dioxide and water
What is the chemical equation for the reaction of methanoic acid with sodium carbonate?
2HCOOH + Na2CO3 → 2HCOO-Na+ + CO2+H2O
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.
What is the chemical equation for the
reaction between methanol and ethanoic
acid? Give the name of the ester formed
CH3OH + CH3COOH → CH3COOCH3 + H2O
Product CH3COOCH3
is methyl ethanoate.
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.
What are biofuels
Fuels from living organisms
Two types of biofuels
Bioethanol
Biodiesel
Advantages of biofuels
Renewable
carbon neutral
Disadvantage of biofuels
Land use
Use of resources
How is ethanol produced
By hydration of ethene
Hydration of Ethene
From cracking hydrocarbons produced from petroleum
Reacts with steam to produce
ETHANOL
conditions for hydration or ethene
300C
60-70 atm
Phosphoric catalyst
Fermentation
Sugars are converted into ethanol
Eg glucose is dissolved in water
Yeast is added
Then mixture is left in warm place
Yeast contains enzymes that catalyses the reaction
Equation for fermentation
C6H12C6——->2C2H5OH + 2CO2
What is an alcohol
Homologous series containing -OH as the functional group
