Alcohols

Question 1

What is the functional group of an alcohol?

Answer 1

Hydroxyl group, -OH

Question 2

What is the general
formula of an alcohol?

Answer 2

CnH2n+1OH

Question 3

How do you name alcohols (one prefix, one suffix)?

Answer 3

Hydroxyl- or -ol

Question 4

What kind of intermolecular forces do alcohols have? Why?

Answer 4

Hydrogen bonding, due the the difference in electronegativity in the OH bond

Question 5

How do alcohols’ melting and boiling points compare to other hydrocarbons’ of similar chain C lengths? Why?

Answer 5

Higher, because they have hydrogen bonding (strongest type of intermolecular force) which are stronger than London forces and require more energy to overcome.

Question 6

Are alcohols soluble in water? Why does solubility depend on chain length?

Answer 6

Soluble when short chain - hydrogen in OH bonds to hydrogen bond in water
Insoluble when long chain - non-polarity of C-H bond takes precedence

Question 7

What makes an alcohol primary?

Answer 7

C bonded to OH is bonded to one alkyl group

Question 8

What makes an alcohol secondary?

Answer 8

C bonded to OH is bonded to two alkyl groups

Question 9

What makes an alcohol tertiary?

Answer 9

C bonded to OH is bonded to three alkyl groups

Question 10

Write an equation for the combustion of ethanol

Answer 10

C2H5OH(l) + 3O2(g) -> 2CO2(g) + 3H2O(l)

Question 11

What forms if you partially oxidise a primary alcohol?

Answer 11

An aldehyde

Question 12

What conditions are needed to partially oxidise a primary alcohol?

Answer 12

Dilute sulphuric acid, acidified potassium dichromate (VI), distill product as it’s produced, gentle heating

Question 13

Write an equation for the partial oxidation of ethanol

Answer 13

CH3CH2OH(l) + [O] -> CH3CHO(g) + H2O(l)

Question 14

What forms if you fully oxidise a primary alcohol?

Answer 14

A carboxylic acid

Question 15

What conditions are needed to fully oxidise a primary alcohol?

Answer 15

Concentrated sulphuric acid, acidified potassium dichromate (VI), reflux and strong heating.

Question 16

Write an equation for the full oxidation of ethanol

Answer 16

CH3CH2OH(l) + 2[O] -> CH3COOH(g) + H2O(l)

Question 17

What forms if you fully oxidise a secondary alcohol?

Answer 17

A ketone

Question 18

What conditions are needed for the oxidation of a secondary alcohol?

Answer 18

Concentrated sulphuric acid, acidified potassium dichromate (VI), strong heating

Question 19

Write an equation for the oxidation of propan-2-ol

Answer 19

CH3CH(OH)CH3(l) + [O] -> CH3COCH3(g) + H2O(l)

Question 20

Is it possible to oxidise tertiary alcohol?

Answer 20

No

Question 21

What is a dehydration reaction?

Answer 21

An elimination reaction where water is lost to form an organic compound

Question 22

What are the products of dehydration reaction of alcohol?

Answer 22

Alkene and water

Question 23

What are the conditions required for dehydration of alcohol?

Answer 23

Concentrated sulphuric acid or concentrated phosphoric acid and 170°C

Question 24

What are the products of halide substitution reaction with alcohol?

Answer 24

Haloalkane and water

Question 25

In what form is the halide used in halide substitution reaction?

Answer 25

In the form of a hydrogen halide, e.g. HBr

Question 26

How is hydrogen halide made in situ? Give examples

Answer 26

A salt is reacted with acid to form the hydrogen halide, e.g. sodium bromide reacts with sulfuric acid to form HBr. When iodine is reacted, phosphoric acid is used as sulfuric acid oxidises iodide ions into iodine.