Alcohols

Question 1

What is the general formula of an alcohol?

Answer 1

CnH2n+1OH

Question 2

Why is the OH bond polar?

Answer 2

The oxygen is more electronegative than the hydrogen.

Question 3

Explain the solubility of alcohols (4 points).

Answer 3

1. The OH group of the alcohol can form hydrogen bonds with water molecules.
2. Whereas the carbon chain forms induced dipole-dipole, so cannot interact with water molecules.
3. Alcohols become less soluble as the carbon chain length increases.
4. The more OH groups a molecule has, the more H bonds will form, the greater its water solubility.

Question 4

Definition of volatility

Answer 4

If a liquid is volatile, it can change from a liquid to a gas easily (by the breaking of intermolecular forces between the molecules), then the boiling point is low.

Question 5

Write the reaction for the combustion of propan-1-ol

Answer 5

CH3H7OH + 9/2O2 …. 3CO2 + 4H2O

Question 6

Write the reaction for the complete combustion of butan-2-ol

Answer 6

C2H9OH + 6O2 …. 4CO2 + 5H2O

Question 7

What oxidising agent is used in oxidation of alcohols?

Answer 7

Acidified potassium dichromate

Question 8

What are the observations of an oxidation of alcohols reaction?

Answer 8

Orange to green colour change

Question 9

Write the half equation which represents the reduction of chromium

Answer 9

Cr2O7^2- + 14H+ + 6e- …. 2Cr^3+ + 7H2O

Question 10

What are the products, reagents and conditions for the partial oxidation of primary alcohols?

Answer 10

Aldehyde
K2Cr2O7(aq)
Concentrated H2SO4(aq)
Distillation

Question 11

Why is distillation used in partial oxidation?

Answer 11

1. Separates solutions with different boiling points. An aldehyde is formed which has a lower boiling point, so is separated.
2. Provides energy for the reaction.
3. Removes the product from the oxidising mixture to prevent further oxidation.

Question 12

What product is formed when a primary alcohol is fully oxidised?

Answer 12

A carboxylic acid

Question 13

Definition of reflux

Answer 13

Continuous evaporation and condensation.

Question 14

What product is formed when an aldehyde is fully oxidised?

Answer 14

Carboxylic acid

Question 15

What product is formed when secondary alcohols are fully oxidised?

Answer 15

A ketone

Question 16

What are the reagents and conditions for the full oxidation of secondary alcohols?

Answer 16

K2Cr2O7 and concentrated H2SO4(aq)
Reflux

Question 17

What is the test for tertiary alcohols?

Answer 17

Cannot be oxidised

Question 18

What acid catalyst can be used to dehydrate primary alcohols?

Answer 18

Concentrated H2SO4(aq) or concentrated H3PO4(aq)

Question 19

What is the name of the reaction for the conversaion of a primary alcohol into an alkene?

Answer 19

Elimination (of H2O)

Question 20

What are the conditions for the elimination reaction of primary alcohols?

Answer 20

Reflux

Question 21

What type of reaction is the conversion of a primary alcohol into haloalkane?

Answer 21

Substitution

Question 22

What are the reagents and conditions for the substitution reaction of primary alcohols into haloalkanes?

Answer 22

Alcohol and sodium halide and concentrated H2SO4(aq)
Heat under reflux

Question 23

What are the two steps for the substitution reaction of a primary alcohol into a haloalkane?

Answer 23

1. Sodium halide + H2SO4(aq) …. hydrogen halide + sodium hydrogensulfate
2. Hydrogen halide + alcohol …. haloalkane + water

Question 24

What type of reaction is esterification with carboxylic acids?

Answer 24

Reversible.
Forwards: condensation
Backwards: hydrolysis