5-O Alcohols Flashcards
What’s the general formula for an alcohol
CnH2n+1OH
When molecules have more than one functional group what is the priority order with prefix
1-Carboxylic acid (no prefix only suffix highest priority)
2-nitrile (cyano) use number to indicate position for rest
3-aldehyde (oxo)
4-ketone (oxo)
5-alcohol (hydroxy)
6-amine (amino)
How to name an alcohol with 1 -OH group
Alkane name, remove e, count which carbon atom it’s connected to (lowest number) then add ol
eg ethanol
eg butan-1-ol
How to name an alcohol with 2 or more -OH groups
Alkane name, add the numbers to which carbon atoms the -OH groups are attached to (lowest numbers), add di, tri, tetra etc, add ol
eg butane-1,4-diol
What’s the reactants/product of hydration and the catalyst
Reactant is an alkene and water (g)
Product is an alcohol
H3PO4 catalyst
How is ethanol made from fermentation
Carbohydrates from plants broken down into sugar by enzymes from yeast then converted into ethanol
Equation for production of ethanol by fermentation and fractional distillation give conditions for each
C6H12O6(aq) —> 2C2H5OH(aq) +2CO2(g)
Anaerobic conditions, prevent ethanol forming ethanoic acid
Compromised temp 35°, enzymes made ineffective at high temps
Yeast catalyst
Solution needs to be aqueous
15% yield of ethanol is then fractionally distilled as it has a boiling point lower than water
What’s a biofuel
A fuel derived or produced from renewable and biological sources
Evaluate whether ethanol produced by fermentation is carbon neutral
Agree
(Photosynthesis) 6CO2 + 6H2O —> C6H12O6 + 6O2
(Fermentation) C6H12O6 —> 2C2H5OH + 2CO2
(Combustion) 2C2H5OH + 6O2 —> 4CO2 +6H2O
6 mol of CO2 absorbed 6mol of CO2 released, not net emissions
Disagree
Energy needed for transport of fuel and processing it is from fossil fuels
Fertiliser required contains carbon
Mechanism for hydration of alkenes is in alkene deck
What are environmental and ethical issues surrounding biofuel use
Land used to grow plants could be used to grow food
How to know if an alcohol is tertiary/3°
The substitute group is on the same C atom as the -OH group
What are 1°, 2°, 3° alcohols
1°, 1 alkyl group attached to carbon with -OH
2°, 2 alkyl groups attached to carbon with -OH
3°, 3 alkyl groups attached to carbon with -OH
What can primary alcohols eg ethanol be oxidised into
Aldehydes, further oxidised into carboxylic acids
1) CH3CH2OH +[O] —> CH3CHO+ H2O
2)CH3CH2OH + 2[O] —> CH3COOH + H2O
How are the methods to produces aldehydes or carboxylic acids from primary alcohols different
Aldehydes
[O] and excess alcohol added into hot H2SO4
Aldehyde distilled off to prevent further oxidation
Carboxylic acids
Heat under reflux, distill off products
Excess [O]
What are secondary alcohols eg propan-2-ol oxidised to
Ketone
CH3CH(CH3)OH + [O] —> CH3COCH3 + H2O
What’s the oxidising agent used to oxidise alcohols
Acidified Potassium dichromate (VI)
Orange solution turns green in presence of primary/secondary alcohol
What happens in oxidation in terms of hydrogen
Loses hydrogen
Ionic equation for reaction of ethanol with acidified dichromate
6ē +14H+ + Cr2O7 2- —> 2Cr 3+ + 7H2O
Need state symbols for ionic eq
Half equation for reaction of ethanol to give ethanal
CH3CH2OH —> CH3CHO + 2H+ + 2ē
Half equation for reaction of ethanol to ethanoic acid
CH3CH2OH + H2O —> CH3COOH + 4H+ + 4ē
How to test for an aldehyde or ketone with fehlings reagent
Aldehyde, blue solution forms a brick red precipitate
Ketone, solution remains blue
How to test for an aldehyde or ketone with tollens reagent
Aldehyde, colourless solutions forms a silver mirror
Ketone, solution remains colourless
What reaction turns alcohols into alkenes
Elimination
Conditions for an elimination reaction
Heat at 180°c
Excess conc H2SO4 (catalyst)
Uses for elimination reactions
Alkenes produced can form additions polymers without the monomer being derived from crude oil
Elimination mechanism on symmetrical alcohols
First arrow: lone pair on the oxygen from the hydroxyl group. The arrow goes from the middle of the lone pair to the H+ catalyst
Second arrow: the oxygen is now bonded to 2 H atoms giving it a +ve charge. The arrow goes from the middle of the carbon oxygen bond onto the oxygen.
third arrow: the C atom has a +ve charge arrow from the middle of the CH bond to the middle of the CC bond.
Elimination mechanism for unsymmetrical alcohols
First arrow: lone pair on the oxygen from the hydroxyl group. The arrow goes from the middle of the lone pair to the H+ catalyst
Second arrow: the oxygen is now bonded to 2 H atoms giving it a +ve charge. The arrow goes from the middle of the carbon oxygen bond onto the oxygen.
third arrow: the C atom has a +ve charge arrow from the middle of the CH bond to the middle of the CC bond, two possible products, form E-Z isomers
Ethanol production by hydration vs fermentation
Hydration
Higher yield
Ethene is non renewable
Equipment is expensive
Fermentation
Glucose is renewable
Cheaper equipment
