4.2.1 Alcohols

Question 1

Alcohols volatility

Answer 1

Relatively low due to their ability to form hydrogen bonds between alcohol molecules

Question 2

General formula for alcohols

Answer 2

CnH2n+1OH

Question 3

Alcohol solubility

Answer 3

Smaller (up to 3 carbons) are soluble as they can form hydrogen bonds with water
Longer the hydrocarbon chain the less soluble the alcohol

Question 4

Uses of alcohols

Answer 4

Ethanol: alcoholic drinks, solvent in the form of methylated spirits
Methanol: petrol additive to improve combustion and is important as a feedstock in the production of organic chemicals

Question 5

Types of alcohols

Answer 5

Primary
Secondary
Tertiary

Question 6

Primary alcohols

Answer 6

Where 1 carbon is attached to the carbon adjoining the oxygen

Question 7

Secondary alcohols

Answer 7

Where 2 carbons are attached to the carbon adjoining the oxygen

Question 8

Tertiary alcohols

Answer 8

Where 3 carbons are attached to the carbon adjoining the oxygen

Question 9

Complete combustion of alcohols

Answer 9

In excess oxygen

Will produce carbon dioxide and water

Question 10

Oxidizing agent for alcohols

Answer 10

Potassium dichromate 6

K2Cr2O7

Question 11

Partial oxidation of primary alcohols

Answer 11

Primary alcohol-> aldehyde
Reagent: potassium dichromate 6, warm gently and distil
Observation: orange dichromate ion (Cr2O7 2-) reduces to the green (Cr3+) ion

Write aldehyde as CHO on end

Question 12

How can you maximize the yield collected in distillation

Answer 12

Approximation of boiling point of desired aldehyde and not higher

Question 13

Full oxidation of primary alcohols

Answer 13

Reaction: primary alcohol-> carboxylic acid
Reagent: potassium dichromate 6 and dilute sulfuric acid
Conditions: use excess of dichromate and heat under reflux, distil off product after reaction has finished
And observations are same: orange to green
NEEDS TWO OXIDISING AGENTS

Question 14

What shouldn’t you do in reflux

Answer 14

Seal the end of the condenser

Build up of gas pressure could cause apparatus to explode

Question 15

What are added to reflux apparatus

Answer 15

Anti-bumping granules added to flask in both distillation and reflux to prevent vigorous, uneven boiling by making small bubbles form instead of large bubbles

Question 16

Oxidation of secondary alcohols

Answer 16

Secondary alcohol -> ketone 
Reagent: potassium dichromate 6 solution and dilute sulfuric acid 
Conditions: heat under reflux 
Observations: orange to green 
No further oxidation

Question 17

Oxidation of tertiary alcohols

Answer 17

Can’t be oxidised by potassium dichromate 6

No hydrogen atom blonde does to the carbon with the OH group

Question 18

Reaction of alcohols with dehydrating agents

Answer 18

Alcohol -> alkene
Reagents: conc sulfuric or phosphoric acid
Conditions: warm under reflux
Role of reagent: dehydrating agent/ catalyst
Type of reaction: acid catalysts elimination

Question 19

Dehydration reaction

Answer 19

Removal of a water molecule from a molecule

Question 20

When can some secondary and tertiary alcohols form more than one product

Answer 20

When double bond forms between different carbon atoms

Question 21

Substitution reactions of alcohols to form haloalkanes

Answer 21

Mixture of halide ions with conc acid NaCl + H2SO4 can be used for substituting a halogen onto an alcohol
Reaction: alcohol -> haloalkane
Reagents: conc sulfuric acid and sodium halide