C Unit 2.7 Alcohols and Carboxylic acids Revamp Flashcards
How do they prepare ethanol?
(2-way)
- Steam and ethene passed over
- a catalyst of phosphoric acid
Write eqn for the preparation of ethanol?
CH2=CH2(g) + H2O(g) ⇌ CH3CH2OH(g)
Temperature for the preparation of ethanol and reason?
(3-way)
- 300°C
- Rxn = exothermic
- High yield
Pressure for the preparation of ethanol and reason?
(3-way)
- 60-70 atms (moles?)
- 2 moles into 1 gas
- High yield
Why is phosphoric acid catalyst used to prepare ethanol?
Just increases the rate
(Overthinking)
What’s the steam:ethene ratio for the preparation of ethanol?
(Optional probably lol)
0.6:1 but aye whatever man
How to make conversion efficient for the preparation of ethanol?
(3-way…. whatevs)
- Steam & ethene recycled
- 5% conversion per pass
- Theoretical atom econ. = 100%
What’s an alternate method to prepare ethanol?
(2-way)
- Fermentation of sugar (glucose)
- from plant material
Write eqn for the preparation of ethanol through fermentation?
C6H12O6 -> 2 C2H5OH + 2CO2
What’s the temperature and the catalyst used for the preparation of ethanol through fermentation?
(1 + 2-way)
- 30°C
- Enzymes in yeast
- are the natural catalysts
How do they actually gain the ethanol through fermentation?
(2-way + 2-way)
- Ethanol separated from remaining liquid mixture
- CO2 escapes as a gas
- BP of ethanol = 80°C
- Use of fractional distillation
Purpose of ethanol through fermentation?
(2 things)
- Alcoholic drinks
- Bioethanol (fuel for motor vehicles)
Define biofuel?
(2-way)
- A fuel produced through contemporary biological processes
- e.g. agriculture & anaerobic digestion
What type of process is the formation of fossil fuels?
Geological processes
The ethical issue of biofuels?
(2-way + 1)
- Use crops to feed people
- than to provide raw materials for biofuels
- May cause food shortages/increase of food price
The 3 economic issues of biofuels?
(take it easy, cuz brief explanation for each)
- Human resources = more people needed for biofuels than petrol/diesel
- Increased income = for farmers
- Lower fuel prices = limits demand for fossil fuels
Environmental issue of biofuels?
(4-way)
- Said to be carbon neutral
- Supposed to reduce productions of greenhouse gas
- True with less CO2 but aren’t carbon neutral
- Fossil fuels used in their production… (making fertilisers)
Define carbon neutral?
(2-way)
- Amount of CO2 released same as
- Amount absorbed by plants as they grow
How to turn an alcohol back into an alkene?
Dehydrating the alcohol
How to dehydrate an alcohol?
(2-way)
- Pass alcohol vapour
- over heated aluminium oxide
Write eqn of ethanol forming alkene through dehydration?
CH3CH2OH(g) -> H2O(g) + CH2=CH2(g)
Alternate of alcohol to an alkene?
(2-way)
- Heated w/ concentrated sulfuric acid (in excess)
- at 170°C
How to distinguish primary alcohols (1°)?
(2-way)
- Carbon carries the -OH group
- Same carbon attached to 1 alkyl group
How to distinguish secondary alcohols (2°)?
(2-way)
- Carbon carries the -OH group
- Same carbon attached to 2 alkyl groups
How to distinguish tertiary alcohols (3°)?
(2-way)
- Carbon carries the -OH group
- Same carbon attached to 3 alkyl groups
Purpose of oxidation of alcohols?
To produce aldehydes/ketones/carboxylic acids
What oxidising agents are used to oxidise alcohols?
(2.)
- Sodium hypochlorite (NaOCl… interesting!)
- potassium dichromate(VI) acidified w/ dilute sulphuric acid
Colour change if oxidation occurs for alcohols?
(Using Acidified potassium dichromate)
Orange to green
If u oxidise primary alcohols, what can you get?
(2 things)
- Aldehydes
- AND, carboxylic acids (fruther oxidised)
Draw oxidation of ethanol creating ethanal or ethanoic acid
Stages’ yours
Draw oxidation eqn of ethanol for just ethanal
GOooooo, don’t forget:
- +H2O
- Pointing out carbonyl bond
Draw oxidation of ethanal for ethanoic acid
Again, but don’t forget reflux
How to actually gain the aldehyde from oxidation of primary alcohols?
(2-way)
- Distill product immediately
- after formation
How to actually gain the carboxylic from further oxidation of primary alcohols?
Reflux the alcohol ig
If u oxidise secondary alcohols, what can you get?
Ketones
Draw eqn of propan-2-ol oxidised gaining propanone
Stages yours’
If u oxidise tertiary alcohols, what can you get?
Nothing, no reaction whatsoever
Why can’t we oxidise tertiary alcohols?
(2-way + 1 point)
- The oxidising agent usually removes H
- From -OH group and H attached to C atom
- Tertiary alcohols don’t have that latter part
U know the colour change for using dichromate(VI). But how do u actually perform the test?
(4-way)
- Few drops of alcohol
- To test tube containing potassium dichromate(VI) sol.
- … acidified with dilute sulphuric acid
- Tube warmed in hot water bath
For testing alcohols, what about the observation for tertiary?
No colour change
How to test for carboxylic acids?
- Use hydrogencarbonate
- Produces salt, CO2 + H2O
Results for when u use hydrogencarbonate on dilute carboxylic acid?
(2-way)
- Immediate fizzing (CO2)
- Colourless solution of “…“-noate
(there’s an example up ahead)
Write symbol eqn of ethanoic acid + sodium hydrogen carbonate?
CH3COOH + NaHCO3 -> CH3COONa + CO2 + H2O
How are carboxylic acids acidic?
(2-way)
- Due to the hydrogen in
- -COOH group
Significance of carboxylic acid being acidic?
(3-way… prob don’t needa deep the list)
- Can react w/
- metals, bases, alkalis, carbonates + hydrogencarbonates
- similarly to inorganic acids
Explain carboxylic acids reacting with bases/alkalis?
(4-way… 1 may be optional)
- Simple neutralisation reaction
- Likewise to H+ ions from acid rxn w/ OH- ions
- May gain colourless solution
- Deduce a change: temperature increase
- Acid + Alkali/Base -> Salt + Water
Write symbol eqn. of dilute ethanoic acid w/ sodium hydroxide solution?
CH3COOH(l) + NaOH(s) -> CH3COONa(aq) + H2O(l)
Write symbol eqn. of ethanoic acid w/ copper(II) oxide?
(Could be wrong… onto ur deduction skills)
2CH3COOH(l) + CaO(s) -> Ca(CH3COO)2 + H2O(l)
Explain carboxylic acids reacting with carbonates & hydrogencarbonates
(3-way)
- Salt formed w/ CO2 + H2O
- It’s pretty much like ur identifying of carboxylic acids
- … Immediate fizzing & colourless solution…
Write symbol eqn. of propanoic acid w/ potassium carbonate?
CH3CH2COOH + K2CO3 -> 2 CH3CH2COOK + CO2 + H2O
What test can you do to identify the gas (CO2) produced?
(2…)
- Pass gas through lime water
- Solution is milky = present
What’s the ester function group look like?
(+ 2-way)
O=C-O
- aka C double bond w/ O
- and single bond w/ O
What happens when an alcohol and a carboxylic acid reacts?
- Esterification, forms an ester (sweet-smelling substance)
- & a small molecule (H2O)
Requirements & Fact for an alcohol and a carboxylic acid to react?
(3-way)
- H2SO4 used as catalyst
- Mixture heated to 70°C
- Reaction is reversible
Write word + structural formula eqn for ethanol + ethanoic acid
Also circle the ester functional group.
All yours pal
Ethanol + ethanoic acid ⇌ ethyl ethanoate + water
How to name esters?
(3-way)
- First part = alcohol
- Second part = carboxylic acid
- e.g. methanol + propanoic acid = methyl propanoate
How is the water molecule created from esterification?
(2-way)
- OH group from carboxylic acid
- H part from alcohol group
How would we really gain the ester from esterification?
(2-way)
- Separation by distillation
- As it has the lowest boiling point
How do we actually perform the distillation of esters?
(4-way)
Ofc after setup:
- Gently heat mixture of alcohol + carboxylic acid
- w/ presence of conc. H2SO4
- Distill off ester as soon as it’s formed
- Also preventing reverse reaction
How come separation by distillation work for esters?
(3-way)
- Ester doesn’t form hydrogen bonds
- Weak intermolecular forces
- Still lowest boiling point
I’d say redeeming but, we’re not done yet
,’:)
