Transcript Alcohols and ethers

This is ethane, an alkane. Alcohols are based on alkanes but with one of the
H atoms replaced by an -OH group.
This is ethanol.
The hydroxyl group is often just shown as -OH.
To name an alcohol you need to know the number of carbon atoms it contains.
This gives the first part of the alcohol's name.
An alcohol is named by adding ol to the prefix given by its number of
carbon atoms.
The total number of hydrogen atoms in an alcohol is twice its number of
carbon atoms, plus two.
But the hydroxyl group is usually treated separately.
It helps to know the prefixes given by the number of carbon atoms and the
general formula.
The structural formula shows how the atoms are bonded together in methanol.
The displayed formula shows all the atoms and all the bonds in methanol.
The skeletal formula shows the functional group but leaves out the carbon
atom and other hydrogen atoms.
And the same information for ethanol.
Alcohols with 3 or more carbon atoms have position isomers. Look at
propanol.
The hydroxyl group can be joined to an end carbon atom or to the one in the
middle.
We number the carbon atoms to tell them apart. If we do it this way, we get
propan-3-ol.
But the number must be the lowest possible, so here we number from the
right, giving propan-1-ol.
The other isomer is propan-2-ol. In this case, it does not matter from which
end we start the numbering.
This is butanol with its hydroxyl group on one of the end carbon atoms.
We use the lowest numbers, so this is butan-1-ol.
This is butanol with its hydroxyl group on one of the middle carbon atoms.
We use the lowest numbers, so this is butan-2-ol.
There is a branched isomer of butanol. The longest chain has three carbon
atoms, so we name it after propanol.
It is 2-methylpropan-1-ol.
There is another branched isomer.
This one is 2-methylpropan-2-ol.
If the carbon atom carrying the hydroxyl group is directly attached to one other
carbon atom, we have a primary alcohol.
If the carbon atom carrying the hydroxyl group is directly attached to two other
carbon atoms, we have a secondary alcohol.
If the carbon atom carrying the hydroxyl group is directly attached to three
other carbon atoms, we have a tertiary alcohol.
Polyhydric alcohols contain more than one hydroxyl group.
This one has two hydroxyl groups, so it is a diol. It is called
ethane-1,2-diol.
This polyhydric alcohol has three hydroxyl groups, so it is a triol.
It is called propane-1,2,3-triol.
Ethers have two carbon atoms joined to an oxygen atom. They have a general
formula R-O-R', where R and R' are alkyl groups.
This is ethoxyethane.
This ether is an 'oxygenate' commonly added to petrol. It is commonly called
MTBE or methyl tertiary butyl ether.
Its systematic name is 2-methoxy-2-methylpropane.
Intermolecular forces must be overcome for simple molecular substances to
boil. The stronger the forces, the higher the boiling point.
Ethanol and methoxymethane have identical molecular formulae and relative
molecular masses. Their boiling points should be similar if instantaneous
dipole-induced dipole forces are the only intermolecular forces to overcome.
Ethanol has a much higher boiling point than methoxymethane as it also has
hydrogen bonds that must be overcome.
Similarly, butanol has a much higher boiling point than ethoxyethane because
it also has hydrogen bonds that must be overcome.