14.1 Properties of alcohols
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What functional group do alcohols contain
-OH Hydroxyl group
What is the hydroxyl group responsible for
Both the physical and chemical properties of the alcohols
What is methanol used for
Simplest alcohol High-performance fuel - efficient combustion Important chemical feedstock - starting chemical in many syntheses, polymers, paints, solvents, insulation
What is ethanol used in
Alcoholic drinks Fuel
Naming alcohols
Adding -ol to stem name of longest carbon chain Position of functional group indicated using number
Differences in physical properties between alcohols and alkanes of the same number of carbon atoms
Alcohols less volatile, have higher melting points and greater water solubility than alkanes
How can the differences in physical properties between alcohols and alkanes of the same number of carbon atoms be explained
Alkanes - non-polar bonds as electronegativity of H and C very similar Intermolecular forces between non-polar molecules are very weak London forces Alcohols have polar O-H bond due to difference in electronegativity of O and H atoms Intermolecular forces very weak London forces but also much stronger hydrogen bonds between polar O-H groups
What must happen for a liquid alcohol to be changed into a gas
Intermolecular hydrogen bonds must be broken Requires more energy than overcoming London forces in alkanes Alcohols therefore lower volatility than alkanes
What word is used to describe compounds with low boiling points
Volatile The higher the boiling point, the lower the volatility
Are alkanes and alcohols soluble in water
Alkanes are non-polar and cannot form H bonds with water Alcohols are completely soluble in water as H bonds form between polar -OH group and water molecules
How does the influence of the -OH group change as a hydrocarbon chain increases in size
The influence decreases Solubility of longer chain alcohols decreases
How can alcohols be classified
As primary, secondary or tertiary
What does the classification of alcohols depend on
The number of hydrogen atoms and alkyl groups attached to the carbon atom that contains the alcohol functional group
How is the -OH attached in a primary alcohol
Attached to a carbon atom that is attached to two H atoms and one alkyl group
How is the -OH attached in a secondary alcohol
Attached to a carbon atom that is attached to one H atom and two alkyl groups
How is the -OH attached in a tertiary alcohol
Attached to a carbon atom that is attached to NO H atoms and three alkyl groups