4.2.1 - Alchols

Question 1

Primary alcohols

Answer 1

• 2 hydrogens attached to the carbon that is attached to the -OH group
• 1 R groups

Question 2

Secondary alcohols

Answer 2

• 1 hydrogen attached to the carbon that is attached to the -OH group
• 2 R group

Question 3

Tertiary alcohols

Answer 3

• 0 hydrogens attached to the carbon that is attached to the -OH group
• 3 R groups

Question 4

Explain the solubility of alcohols

Answer 4

• Shorter chains are more soluble than longer chains.
• The hydroxyl (polar) group in the shorter chains dominate in the molecule so hydrogen bonds can be formed between the alcohol and water,
• The alkyl group(the carbon chain which non polar and is now longer) dominates and interferes with the hydrogen bonds between the -OH group and water

Question 5

What type of bonding is in alcohols

Answer 5

Hydrogen bonding
and london forces

Question 6

Blurt everything you know about alcohols to haloalkanes including the reagents, and an example : ethanol goes to ?

Answer 6

Reagents: Concentrated sulfuric and sodium halide
Conditions: Heat under reflux
nucleophilic substitution

Question 7

Blurt everything you know about oxidation of Primary Alcohols

Answer 7

-Primary alcohols > Aldehyde > Carboxylic acids
- Reagent: acidified potassium dichromate (VI) (looks yellow)
- Conditions: Distillation
- In bothe cases we observe a colour change from orange to green
- Aldehydes can be oxidised further into carboxylic acids. Acidified potassium dichromate is the reagent but this time
conditions = heat under reflux

Question 8

Blurt everything you know about oxidation of Secondary Alcohols.
Use an example: Propan-2-ol

Answer 8

• Secondary alcohols can only be oxidised once.
• They are oxidised into ketones.
• Reagents : acidified potassium dichromates (K2Cr2O7) or sulfuric acid (H2SO4).
• Conditions: Heat under reflux
• Observation: the
  orange dichromate
  ion (Cr2O7
  2-) reduces
  to the green Cr 3+ ion

Question 9

Why can’t tertiary alcohols be oxidised ?

Answer 9

Tertiary alcohols cannot be oxidised at all by potassium dichromate: This is because there is no hydrogen
atom bonded to the carbon with the OH group.

Question 10

Blurt everything you know about alcohols to alkenes including the reagents. Use the example of Propan-1-ol and butan-2-ol.

Answer 10

Reagents: Concentrated sulfuric or phosphoric acid (H3PO4 or H2SO4).
Conditions: heat (under reflux)
Role of reagent: dehydrating agent/catalyst
Type of reaction: acid catalysed elimination
- H2O is produced
- Example of a dehydration reaction.
- Mechanism not required

Question 11

Blurt everything you know about alcohols to haloalkanes including the reagents. Use the example of ethanol

Answer 11

Reagents: Concentrated
sulfuric acid and sodium halide
- Mechanism not required

Question 12

Explain what you know about the volatility of alcohols compared to alkenes

Answer 12

How easy a substance can evaporate into a gas.
- Alcohols: Less volatile(less able) due to strong hydrogen bonding between molecules.
- Alkenes: More volatile due to weaker Van der Waals forces.

Question 13

Blurt everything you know about the polarity of alcohols.

Answer 13

• The -OH group in alcohols makes them polar because of the electronegativity difference between oxygen and hydrogen.
• The presence of the polar -OH group makes alcohol molecules polar overall

Question 14

Blurt everything you know about the combustion of alcohol including an example (the combustion of ethanol)

Answer 14

Question 15

Draw a distillation setup

Answer 15

Water in is ALWAYS at the bottom

Question 16

Draw a reflux set up

Answer 16

Water in is ALWAYS at the bottom