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Alcohols and Ethers
AH Chemistry Unit 3(b)
Alcohols
Physical properties
• When comparing the boiling point of
ethanol with an alkane, which alkane
would you compare it with?
• Which would have the higher boiling
point?
• Why?
• Alcohols exhibit hydrogen bonding.
• As a result, they exhibit higher boiling
points than (most) other organic
compounds of similar molecular mass.
• Which is more soluble in water: ethanol
or hexan-1-ol?
• Why?
• The lower alcohols are miscible with
water but as their chain length increases
their solubility in water decreases.
Preparation of alcohols
• There are 2 principle methods for
producing alcohols in industry.
What are they?
1. Acid-catalysed hydration of alkenes
(electrophilic addition)
2. Nucleophilic substitution of
halogenoalkanes
Reactions of alcohols
• With metals
– produces alkoxides
• Dehydration
– produces alkenes
• With carboxylic acids
– produces esters, slowly
• With acid chlorides
– produces esters, more vigorously
Acid chlorides
Carboxylic acids can be converted into acid
chlorides by reaction with:
– Thionyl chloride
– Phosphorus(III) chloride
– Phosphorus(v) chloride
Producing esters
• Use full structural formulae to illustrate
how ethyl propanoate can be produced
from an alcohol and an acid chloride.
• What type of reaction is this?
Ethers
General formula
Uses
• Solvents
• Reasons:
– Dissolve many organic compounds
– Volatile (so removed easily by distillation)
Preparation of ethers
• Q: How can you prepare an ether in the
lab?
• A: Reaction of a halogenoalkane with a
metal alkoxide.
• Q: What type of reaction is this?
• A: Nucleophilic substitution
Naming ethers
Methoxyethane
Methoxymethane
Ethoxypropane
Naming Ethers
• Name the longest continuous chain
e.g. pentane
• Name the alkoxy group by removing “yl”
from the substituent name and adding
“oxy” e.g. propyl becomes propoxy
• Add the appropriate number in front of
the substituent if the ether is branched
e.g. 3
• Name a halogenoalkane and metal alkoxide
combination you could use to prepare
ethoxybutane.
• Name a halogenoalkane and metal alkoxide
combination you could use to prepare
2-ethoxybutane.
• Name the ether produced by reacting 1chloropropane with sodium ethoxide.
Physical properties – mp / bp
• How do the melting and boiling points of
ethers compare to alcohols?
• Why?
Physical properties - solubility
• Why are ethers of low molecular mass
soluble in water?
Chemical properties
• Flammable
• Form peroxides on exposure to air / light
(these are unstable and explosive)
e.g. ethoxyethane peroxide