2.7 Alcohols and Carboxylic Acids Flashcards
Miscibility (how easily a liquid mixes with water)
Smaller chain alchohols are miscible in water due to the their ability to hydrogen bond with water molecule. When mixed, new water alcohol hydrogen bonds form, possible as is no significant difference in energy when it happens
Volatility (measure of ease of a liquid turning into vapour)
Alcohols have a higher bp and hence a lower volatility due to the presence of hydrogen bonding and van der Waals.
Industrial Production
Addition reaction of ethene with steam in the presence of phosphoric (H3PO4) catalyst. Requires high temps (300 degrees) and pressure (60-70atm)
Has a 5% conversion rate so remaining ethene is recycled
+ 100% atom economy
- low percentage yield
Fermentation
Used to produce alcoholic drinks, yeast catalyst required and kept at body temp (25-40) . Distillation required for seperation
C6H12O6 –> 2C2H5OH + 2CO2
sugar cane
- not 100% atom economy
Biofuels
Biofuels are produced by living organisms:
Bioethanol -> obtained from sugar in plants
Biodiesel -> Obtained from oils and fats from seeds in plants
+ Carbon neutral
+ Renewable
+ Economic and political security
- Large land use
- use of resources - water,fertilisers
- carbon neutral? - fuel required to build factories and transport
Dehydration
Sulfuric acid or phosphoric acid
heat (180) and Al2O3
ethanol —> ethene + H2O
butan-2-ol —-> but-1-ene/but-2-ene + H2O
Oxidation Of Alcohols
Primary
C2H5OH + [O] -> (heat + distil, H+/Cr2O72-) CH3CHO (ethanal)
C2H5OH + 2[O] -> (heat + reflux, H+/Cr2O72-) CH3COOH (ethanoic acid)
Secondary
C3H7OH + [O] -> (heat + reflux, H+/Cr2O72-) CH3COHCH3 (propanone)
Tertiary
Does not undergo oxidation as there is no hydrogen to remove on C attached to OH group
acidified dichromate (VI) ion will turn from orange to green in primary/secondary oxidation due to it being reduced
Carboxylic Acids
Soluble as h bonds are present but solubility decreases with size of molecule as OH (polar) part is becoming less significant
High bp due to permanent dipole-dipole interactions (C=O) and h bonds (O-H). Bp increases with size of carboxylic acids due to stronger van der Waals
Carboxylic Acids Reactions
With metals:
2CH3CH2COOH + Mg —> (CH3CH2COO)2Mg + H2
With bases:
HCOOH + NaOH —-> HCOOHNa + H2O
With carbonates and hydrogen carbonates:
2CH2COOH + CaCO3 —-> (CH2COO)2Ca + H2O + CO2
CH2COOH + NaHCO3 —–> CH3COONa + H2O + CO2
Carboxylic Acids -> Esters
Conc H2SO4 Catalyst
Ethanol + Ethanoic acid -> ethyl ethanoate + water
Properties of esters
Insoluble in water
lower bp (permanent dipole)
fruity odour
Draw Reflux and Distillation apparatus
Reflux - liquid evaporates, vapour goes into condenser, cools and turns into liquid. Slow reaction, allows time for equilibrium to be established.
