3.3.5 Alcohols

Question 1

Does propan-1-ol or butane have a higher boiling point and why. (4)

Answer 1

-Both have similar strength Van der Waal forces between molecules (similar number of electrons)
-Propan-1-ol has hydrogen bonding between molecules
-Therefore will require more energy to overcome the intermolecular forces between neighbouring molecules of propan-1-ol
-Therefore higher boiling point

Question 2

Explain why propan-1-ol is more soluble in water than butane.

Answer 2

-The electronegativity difference between O and H means that alcohols can form hydrogen bonds with water

-Alkanes do not have any polar bonds that can form hydrogen bonds or permanent dipole-dipole interactions with water

Question 3

Explain why propan-1-ol is more soluble in water than hexan-1-ol.

Answer 3

.The shorter the hydrocarbon chain the more soluble the alcohol is.

.Hydrogen bonding with water is more prevalent in shorter alcohols.

.In longer chain alcohols the large non-polar chain dominates, meaning it is insoluble.

Question 4

What does partial oxidation of primary alcohol form? what is the reagent and conditions

Answer 4

makes an aldehyde

reagent: acidified potassium dichromate
conditions: warm gently, distil out aldehyde as it forms

Question 5

How do we stop aldehydes forming carboxylic acids?

Answer 5

aldehydes have a lower boiling point than carboxylic acids so can be distilled off preventing further oxidation to a carboxylic acid