CI 13.2 – Alcohols and Ethers
(C) JHUDSON 2005
Draw two different structures with
the molecular formula C2H6O
Remember carbon bonds to 4
other atoms, oxygen bonds to 2
Ethanol (an alcohol)
Methoxymethane (an ether)
Alcohols
All alcohols contain the hydroxyl
functional group -OH and have
similar chemical properties
Ethanol can be represented any of these ways;
Naming Alcohols
Full structure
formula
Skeletal
formula
Name
Ethanol
Propan-1-ol
Propan-2-ol
Full structure
formula
Skeletal
formula
Name
Butan-1-ol
Pentan-1-ol
Butan-2-ol
Pentan-3-ol
Physical Properties of Alcohols
Like water molecules, alcohols are polar
due to the electronegativity of the oxygen
atom. Alcohol molecules can hydrogen
bond to each other and to water molecules.
This explains their solubility in water.
At room temperature ethanol is a liquid
whilst ethane is a gas. Can you explain why?
Ethanol has a higher boiling point because
the attractive forces between its molecules
are greater. The intermolecular bonds must
be broken to form a gas.
Alcohol molecules can hydrogen bond to
water molecule so alcohols are soluble in
water.
For bigger alcohol molecules the influence of
the OH group becomes less. So longer chain
alcohols are less soluble.
Ethers
Methoxyethane
Methoxymethane
We can think of ethers as like water molecules with
both hydrogen atoms replaced by alkyl groups.
No hydrogen bonding can occur and the molecules
are only slightly polar so boiling pts are similar to
alkanes with similar mass.