Alcohols Flashcards
(42 cards)
What is the general formula of alcohols?
CnH2n+1OH
Why do alcohols have a higher melting and boiling point than alkanes of similar chain length? (1)
Because alcohols have an OH group they have hydrogen bonding between molecule so higher melting and boiling point
Why do short alcohol molecules dissolve well in polar solvents but longer alcohol molecules dissolve better in non-polar solvents? (1)
Because hydrogen bonds form about the OH group but not about the non-polar alkyl chain of the molecule
What are some of the uses of ethanol? (5)
As an intermediate in the synthesis of other organic chemicals
As a solvent in cosmetics and perfumes
In the manufacture of drugs, detergents and inks
The alcohol found in alcoholic drinks
Biofuel
What is the name of the reaction that is used to produce ethanol from crude oil?
Hydration of ethene
What conditions are needed for hydration? (4)
Concentrated phosphoric (H3PO4) catalyst
Steam
450 degrees Celsius temperature
50-100 atm pressure
Hydration occurs via which mechanism?
Electrophilic addition
What is the reaction called which produces ethanol by fermentation?
Anaerobic respiration/fermentation
What are the conditions needed for fermentation? (3)
Yeast enzymes
Temp - 35 degrees Celsius
No oxygen
Why should no oxygen be present when producing ethanol from fermentation? (1)
Because the ethanol formed may oxidise to ethanoic acid
What are the advantages of hydration of ethene to produce ethanol? (5)
Large scale production method
High purity product made
Readily available raw material
High rate of reaction
Continuous production method
What are the disadvantages of hydration of ethene? (3)
High temperature and pressure needed which increases costs
Expensive and high tech equipment needed
Crude oil is non-renewable
What are the advantages of fermentation? (4)
Uses renewable resources
Low tech method so suitable for developing countries as little expensive equipment needed
Low costs
Low temperature needed
What are the disadvantages of fermentation? (5)
Slow rate of reaction
Impure ethanol made needs distilling
Causes food prices to rise if crops are used to produce alcohol instead of food
Batch production method so less efficient
Low atom economy
What are biofuels?
A fuel produced from renewable plant material
What are the advantages of biofuels? (5)
Can be considered to be carbon neutral
Come from renewable raw materials
Helps to conserve crude oil supplies
Provide employment for farmers to grow crops
Companies with no oil reserves can still generate their own fuel
What are the disadvantages of biofuels? (4)
There are many other carbon costs in their production meaning they are not carbon neutral
Food prices rise as crops used for biofuels therefore an increase market price
Supply of biofuels dependent on crop harvest so less reliable
Biofuels cannot be made on a scale to meet global demands for fuels
What is the most common oxidising agent for alcohols?
Acidified potassium dichromate
What are primary alcohols oxidised to and what are the conditions needed? (4)
Aldehydes
Dilute H2SO4
Potassium dichromate
Distillation
What is the observation when primary alcohols are oxidised to aldehydes under distillation?
Orange to green
Outline the process of distillation (6)
Turn the water supply on to the condenser
Heat the flask
Ethanol will vaporise
Use a thermometer to maintain the temperature at the boiling point of ethanal
The ethanol vapours condense back into a liquid in the condenser
The ethanol is collected in a cooled container to avoid it vaporising
How do primary alcohols produce carboxylic acids? (4)
Oxidation
Conc H2SO4
Potassium dichromate
Reflux
What is the observation when primary alcohols are oxidised to carboxylic acid under reflux?
Changes from orange to green
Outline the process of reflux (5)
Connect the condenser vertically and turn the water supply on
Heat the flask
Ethanal will form by oxidation and will vaporise
The ethanal will condense on the side of the condenser and fall back into the reaction container
The ethanal will oxidise again to form ethanoic acid
