Alcohols (FG, shape, classification & physical properties)

Question 1

What is the alcohol functional group?

Answer 1

-Hydroxyl (OH)

Question 2

What is the shape and bond angle around the oxygen in an alcohol?

Answer 2

Non-linear, 104.5 degrees.
2 lone pairs and 2 bonding pairs so unequal repulsion

Question 3

How can alcohols be classified and what does this depend on?

Answer 3

Primary, secondary or tertiary. Depends on number of alkyl groups bonded directly to the OH carbon

Question 4

What is methanol classified as?

Answer 4

A primary alcohol even though it only has hydrogens bonded to the OH carbon

Question 5

How does boiling point in alcohols change in comparison to their alkanes?

Answer 5

Alcohols always have a higher boiling point but the gap narrows as the carbon chain gets longer.
Alcohols have higher boiling points that corresponding alkanes due to H bonding between OH groups. More energy is needed to overcome intermolecular forces. H bonds plus induced dipole-dipole.
As carbon chain get longer, number of electrons in molecules increases so induced dipole-dipole forces get stronger and narrow the gap in boiling point. Influence of H bonding is less significant.

Question 6

What are alcohols solumbe in?

Answer 6

Water. For this, the energy releases when H bonds form between alcohol and water has to overcome intermolecular forces between alcohol molecules.

Question 7

How does alcohol solubility in water change?

Answer 7

Small alcohols are infinitely soluble.
Longer alcohols become less soluble due to increasing induced dipole forces between the alcohol molecules as carbon chain gets longer.