Condensation & Redox - Organic Reactions & Mechanisms (8.3)

Question 1

Give 2 types of condensation reactions

Answer 1

Esterification

Amide/Protein synthesis

Question 2

Give the reactants used in esterification

Answer 2

Alcohol
+ Carboxylic acid derivative
+ Catalyst

Question 3

Give the reactants used to make amides (proteins)

Answer 3

Amine
+ Carboxylic acid derivative
+ Catalyst

Question 4

In organic chemistry what is usually being oxidised or reduced?

Answer 4

Carbon

Question 5

Give an alternative definition of oxidation (not to do with adding/removing electrons)

Answer 5

Addition of oxygen
OR
Removal of hydrogen

Question 6

Give an alternative definition of reduction (not to do with adding/removing electrons)

Answer 6

Loss of oxygen
OR
Addition of hydrogen

Question 7

Give an example of an oxidising agent

Answer 7

Acidified potassium dichromate

Question 8

Describe the colour change from Cr(VI) -> Cr(III)

Answer 8

Orange -> Green

Question 9

Give an example of 2 reducing agents

Answer 9

Lithium aluminium hydride (LiAlH4) &
Sodium borohydride (NaBa4)

Question 10

Give an advantage and disadvantage of using LiAlH4 as a reducing agent

Answer 10

+ Very reactive

- Requires dry solvent

Question 11

Give an advantage and disadvantage of using NaBH4

Answer 11

+ Does not need dry conditions

- Won’t reduce carboxylic acids

Question 12

What can we use to symbolise oxidising & reducing agents in organic chemistry?

Answer 12

[O] (oxidising agent)

[H] (reducing agent)

Question 13

Ketones can be oxidised. True or false?

Answer 13

False. Ketones cannot be oxidised

Question 14

Tertiary alcohols cannot be oxidised. True or false?

Answer 14

True

Question 15

What are the main uses of the potassium dichromate test?

Answer 15

• Oxidation gives a positive test for aldehydes & 1°/2° alcohols
• It can distinguish between 1°/2° and 3° alcohols
• It can distinguish between aldehydes & ketones

Question 16

How do you test for aldehydes using Fehling’s solution?

Answer 16

Blue sol -> red/orange ppt

Question 17

How do you test for aldehydes using Tollen’s reagent?

Answer 17

[Ag(NH3)2+)])

Colourless sol -> gives silver mirror (solid Ag)

Question 18

What happens to ketones in Fehling’s solution?

Answer 18

No change (remains blue)

Question 19

What happens to ketones in Tollen’s reagent?

Answer 19

No change (remains colourless)

Question 20

How do you make aldehydes?

Answer 20

• Primary alcohols are oxidised under reflux
• A reflux allows us to boil the solvent without it evaporating
• The aldehyde is removed by distillation before it is oxidised before it is oxidised further

Question 21

How do you make ketones?

Answer 21

• Secondary alcohols are oxidised under reflux

- A reflux allows us to boil the solvent without it evaporating

Question 22

What happens if you heat the reaction with primary alcohols strongly?

Answer 22

Carboxylic acid is formed