Chapter 14 Properties of alcohols

Question 1

Why do alcohols have a higher boiling point than alkanes?

Answer 1

Alcohols contain polar O-H groups which create Hydrogen bonds and therefore has more intermolecular forces to overcome whereas an alkane does not have hydrogen bonds and less forces to overcome

Question 2

Why are alcohols more soluble in water than alkanes?

Answer 2

Alcohols contain a polar O-H group which can create H-Bonds in water and dissolve whereas an alkane only contains non-polar bonds and are unable to form hydrogen bonds in water

Question 3

Why do alcohols have a lower volatility than alkanes?

Answer 3

In the liquid state, hydrogen bonds hold the alcohol molecules together and these bonds must be broken in order to change state which requires more energy than overcoming the weaker london forces in alkanes

Question 4

How do you classify an alcohol?

Answer 4

Primary has the -OH on carbon, attached to 2 hydrogen and 1 alkyl group

Secondary has the -OH on carbon, attached to 1 hydrogen and 2 alkyl group

Tertiary has the -OH on carbon, attached to 0 hydrogen and 3 alkyl group

Question 5

How do you oxidise an alcohol?

Answer 5

Alcohols can be oxidised by adding an oxidsing agent of K2Cr2O7 acidified with dilute sulfuric acid

Question 6

When oxidising an alcohol, how do you ensure the product is an aldehyde?

Answer 6

Preparing with distillation rather than reflux

Question 7

What colour change is present when oxidising an alcohol?

Answer 7

Orange to Green

Question 8

What is a dehydration reaction?

Answer 8

A reaction in which a water molecule is removed from the starting material

Question 9

Describe a dehydration reaction with an alcohol

Answer 9

The alcohol is heated under reflux in the presence of an acid catalyst such as conc sulfuric acid

The product is an alkene and water

Question 10

Describe a substitution reaction with an alcohol

Answer 10

Alcohols react with hydrogen halides to form haloalkanes