Alcohols Flashcards
What functional group do ALL alcohols contain?
-OH functional group
What colour are alcohols?
colourless
What kind of solution do alcohols create when they dissolve in water?
neutral solutions
What are the first four alcohols in order?
methanol
ethanol
propan-1-ol
butan-1-ol
What is the -OH functional group responsible for in an alcohol?
the -OH functional group is responsible for an alcohols characteristic reactions
What is the molecular formula for the alcohol methanol?
CH3OH
What is the molecular formula for the alcohol ethanol?
C2H5OH
What is the molecular formula for the alcohol propan-1-ol?
C3H7OH
What is the molecular formula for the alcohol butan-1-ol?
C4H9OH
What does the displayed formula for methanol look like?
should have drawn it right mate
What does the displayed formula for ethanol look like?
should have drawn it right mate
What does the displayed formula for propan-1-ol look like?
should have drawn it right mate
What does the displayed formula for butan-1-ol look like?
should have drawn it right mate
In terms of the naming system for the first four alcohols, what else uses the same system with different endings for the words?
alkanes and alkenes but the alcohols end with an ‘ol’ instead
For the first four alcohols, what is the oxygen (O) from the functional group -OH attached to in the displayed formula?
the O in -OH is attached to a carbon (C) at the end
What are the 3 different ways that ethanol can be oxidised?
-burning in air or oxygen (complete combustion)
-reaction with oxygen in the air to form ethanoic acid (microbial oxidation)
-heating with potassium dichromate (VI) in dilute sulfuric acid to form ethanoic acid (treatment with an oxidising agent)
When alcohols e.g. ethanol undergo complete combustion what do they form?
carbon dioxide + water
(complete combustion)
What kind of flame does ethanol burn with during complete combustion?
an almost invisible blue flame
During microbial oxidation of ethanol, how is the ethanol oxidised?
the microorganisms in the air (acetobacter) use oxygen from the air to oxidise ethanol and form ethanoic acid
What will the microbial oxidation of ethanol produce?
it will produce a weak solution of the carboxylic acid, ethanoic acid, which is the same acid used in vinegar
What kind of acid is ethanoic acid?
carboxylic acid
What happens when ethanol is heated with potassium dichromate (VI) solution in dilute sulfuric acid?
ethanol oxidises to ethanoic acid
What is the equation for the oxidation of ethanol when reacting with potassium dichromate (VI) solution in dilute sulfuric acid?
CH3CH2OH + [O] —> CH3CO2H + H2O
[O] = potassium dichromate acidified with dilute sulfuric acid
What is the colour change when ethanol is being oxidised by potassium dichromate (VI) solution in dilute sulfuric acid when HEATING?
orange —> green
Is the reaction for the oxidation of ethanol with potassium dichromate (VI) with dilute sulfuric acid fast or slow?
its a slow reaction so the mixture is heated for about an hour
What is placed above the reaction flask for the oxidation of ethanol with potassium dichromate (VI) with dilute sulfuric acid and why?
a condenser to avoid the substances evaporating and prevents volatile liquids from escaping
What is the molecular formula for ethanoic acid?
C2H4O2
What does the displayed formula for ethanoic acid look like?
should have drawn it right mate
How many double bonds are there in ethanoic acid and if there is what is it between?
there is 1 double bond between a carbon (C) and oxygen (O) atom
What are the two ways that ethanol can be manufactured?
-(hydration of ethene) reacting ethene with steam in the presence of a phosphoric acid catalyst at a temperature of about 300*C and a pressure of about 60-70 atmospheres
-the fermentation of glucose, in the absence of air, at an optimum temperature of about 30*C and using the enzymes in yeast
What is ethene a by-product of and what are its uses?
the cracking of hydrocarbons and is a valuable feedstock for making many chemicals
What are the exact conditions needed for the hydration of ethene to create ethanol?
-temperature of around 300*C
-pressure of 60-70 atmospheres
-phosphoric acid as a catalyst
How pure is the ethanol that the hydration of ethene produce?
forms 100% pure ethanol (no purification needed)
Is the method for hydration of ethene to form ethanol sustainable or not and why?
it is NOT sustainable as it comes from a non-renewable source
also ethene comes from crude oil so more energy is needed
In terms of time and speed, what kind of process is the hydration of ethene to create ethanol?
it is a fast continuous process
How is the ethanol, ethene and water separated after the reaction from the hydration of ethene to create ethanol?
ethene is separated easily as it has a much lower boiling point than ethanol and water
ethanol and water are separated by fractional distillation
What is the molecular formula of ethene?
C2H4
Does ethene have a double bond?
YES as it is an unsaturated hydrocarbon (alkene)
How can ethanol be produced by fermentation?
ethanol can be produced by fermentation where sugar or starch is dissolved in water and yeast is added
What are the conditions needed for fermentation to create ethanol?
-optimum temperature of 30*C with the absence of oxygen for a few days with enzymes PRESENT to break down sugar
-anaerobic respiration to prevent oxidation further as yeast respires anaerobically
What does yeast respiring anaerobically using glucose produce?
ethanol + carbon dioxide
What is the chemical reaction of yeast anaerobically respiring using glucose to produce ethanol and carbon dioxide?
C6H12O6 —> 2CO2 + 2C2H5OH
At what concentration of alcohol (ethanol) is the yeast killed off in the fermentation method?
once the alcohol reaches around 15% concentration
What happens after the alcohol (ethanol) reaches around 15% concentration?
the process is repeated adding yeast each time to increase the concentration of ethanol
At the end of the fermentation method to produce ethanol, what is left and how is it separated?
at the end there is a mixture of ethanol and water which is separated by fractional distillation
Is the fermentation method to create ethanol sustainable and if it is why?
YES because it comes from renewable sources (sugar comes from plants) and less energy is needed
In terms of time and speed, is the fermentation method to create ethanol fast?
20-60 hours as it is a slow process and a BATCH PROCESS
How pure is the ethanol produced using the fermentation method?
around 51% pure so fractional distillation is needed
(disadvantage)
Why is temperature of specific in the fermentation method for the production of ethanol?
above 40⁰ the enzymes would permanently lose their structure (denature).
at a temperature lower than 30⁰ the process would be too slow
What are the two risks of air being present in the fermentation method for the production of ethanol?
fermentation is conducted in the absence of air. In the presence of air (aerobic conditions), enzymes in the yeast produce carbon dioxide and water instead of ethanol
also in the presence of air the ethanol can oxidise to ethanoic acid