Why boiling point of alcohol is higher than ether?
Oxygen is
more electronegative than hydrogen. For
this reason, O – H bond of alcohol is
polar one.
As a result , alcohol molecules can form inter molecular hydrogen
bond, through which alcohol molecules become associated and they are staying
as gigantic molecule.
Hence, a
large amount heat energy is required to break this large number of hydrogen
bond .Consequently,
the boiling point of alcohol molecule is very much higher.
On the other
hand , ether molecules are slightly polar. So, among the ether molecule ,a
weak dipole-dipole force of attraction act.
Therefore,
to separate these ether molecule a less amount of heat energy is required .
Consequently,
the boiling point of ether is less than
alcohol .
For example
, the molecular weight of ethanol (46) is same as the molecular weight (46) of dimethyl ether.
Yet, the boiling
point of ethanol is 78.7ᵒC
whereas the boiling point of dimethyl ether is – 24.9ᵒC.
Why
solubility of alcohol in water decreases with increasing molecular mass ?
Why solubility of alcohol in water decreases with increasing molecular mass ?
Alcohol is
soluble in water due to formation of inter molecular hydrogen bond with water
molecule .
But, with increasing molecular mass the solubility of alcohol in water gradually decreases and ultimately alcohol with higher mass are insoluble in water.
But, with increasing molecular mass the solubility of alcohol in water gradually decreases and ultimately alcohol with higher mass are insoluble in water.
This is due
to the fact that alcohol with lower molecular mass can form inter molecular
hydrogen bond with water molecule easily.
Because, in case of lower alcohol
the priority of polar hydrophilic part ( - OH )
more prominent than non polar hydrophobic part ( -R ,alkyl group ).
On the other
hand, in case of higher alcohol that is alcohol with higher molecular mass,
the non polar hydrophobic part of alcohol ( - R , alkyl group ) is more
prominent than polar hydrophilic part ( -OH ).
Hence, these
alcohol have low tendency to form hydrogen bond with water molecule .
Consequently,
they are insoluble in water .
Why the boiling point of alcohol is higher than alkane?
Oxygen is
more electronegative than hydrogen. For
this reason, O – H bond of alcohol is
polar one.
As a result , alcohol molecules can form inter molecular hydrogen
bond , through which alcohol molecules become associated and they are staying
as gigantic molecule.
Hence, a
large amount heat energy is required to break this large number of hydrogen
bond .Consequently,
the boiling point of alcohol molecule is very much higher.
On the other
hand, alkane are completely non polar. So, a weak Vander waals force of
attraction acts among the alkane molecules, that is alkane molecules are
staying as individual molecule.
Hence, to
separate these alkane molecule a very much less amount of heat energy is
required.Consequently,
the boiling point of alkane is very much less than alcohol.
For example
, the molecular weight of ethanol (46) is near about same as the molecular
weight of propane ( 44 ).
But, the
boiling point of ethanol is 78.7ᵒC
where as the boiling point of propane is - 42ᵒC which is very much less.
Summary
- Why boiling point of alcohol is higher than ether ?
- Why solubility of alcohol in water decreases with increasing molecular mass ?
- Why the boiling point of alcohol is higher than alkane ?
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