Properties Of Alcohols

Question 1

How does an alcohols properties compare to its corresponding alkane?

Answer 1

1. Less volatile
2. Higher melting points
3. Great water solubility

Differences become much smaller as carbon chain length increases

Question 2

How do alcohols bonds relate to their properties?

Answer 2

• have polar O-H bonds because of the difference in electronegativity between oxygen and hydrogen atoms
• so alcohol molecules are polar
• the intermolecular forces are very weak London forces between molecules but, much stronger hydrogen bonds between the polar O-H groups

Question 3

Why are alcohols less volatile than alkanes?

Answer 3

1. In liquid state, intermolecular hydrogen bonds hold the alcohol molecules together
2. These bonds must be broken in order to change the liquid to a gas
3. This requires more energy than overcoming London forces in awakens, so alcohols have a lower volatility

Question 4

What is the general relationship between boiling points and volatility?

Answer 4

As boiling point increases, volatility decreases.

Question 5

Why are short chain alcohols be completely soluble in water?

Answer 5

1. Hydrogen bonds from between polar O-H group of the alcohol and the water molecules
2. Longer hydrocarbon chains are less or not soluble as:
   
   • the influence of the -OH group becomes relatively smaller
   • a larger part of the molecule is made up of a non-polar hydrocarbon chain which can not form hydrogen bonds with water molecules

Question 6

What is a primary alcohol?

Answer 6

The -OH group is attached to a carbon atom that is attached to two hydrogen atoms and one alkyl group.

Question 7

What is a secondary alcohol?

Answer 7

-OH group is attached to a carbon atom that is attached to one hydrogen atom and two alkyl groups.

Question 8

What is a tertiary alcohol?

Answer 8

-OH group is attached to a carbon atom that is attached to three alkyl groups.