carbonyl compounds

Question 1

What are carbonyl compounds?

Answer 1

An aldehyde or ketone (containing C=O bond).

Question 2

Are carbonyls soluble and if so, why and which ones?

Answer 2

● Yes as it forms hydrogen bonds. ● The small ones.

Question 3

How is Tollens’ Reagent formed? (aka ammoniacal silver nitrate)

Answer 3

1. By mixing NaOH (aq) to AgNO3 (aq) until a brown ppt is formed.
2. Adding dilute ammonia drop-by-drop until the ppt re- dissolves.

Question 4

how is a positve tolkien’s regent test formed

Answer 4

Aldehydes are oxidised by Tollens’ into carboxylic acids with Ag+ ions being reduced and coating inside of the test tube with a silver mirror:
Ag+ (aq) + e- → Ag (s)

This cannot happen with ketones as they cannot be oxidised.

Question 5

How is Brady’s Reagent used • to identify carbonyls? And
how does it react? (4)

Answer 5

Reacts with carbonyls to form a orange/yellow ppt (1)
(2)
● Recrystallise and determine melting point (3)
● Compare to database values (4)

Question 6

How are carbonyls reduced to alcohols? (without catalyst method) (reagents, conditions, mechanism,
example equation)

Answer 6

NaBH4 is used as a source of hydride (H-) ions. In ethanol solution.
Mechanism:
● Examples:
○ CH3CH2CHO + 2[H] → CH3CH2CH2OH
○ CH3COCH3 + 2[H] → CH3CH(OH)CH3
[H] just means some reducing agent.

Question 7

How can carbonyls be converted to alcohols? (with CATALYST) (type, reagents, conditions, example)

Answer 7

● Type: reduction.
● Reagents: H2 and nickel catalyst.
● Conditions: high pressure.
● Examples: CH3CHO + H2 → CH3CH2OH

Question 8

What are nitriles?

Answer 8

An organic compound that has a C≡N functional group

Question 9

How can carbonyls become hydroxynitriles and why would you do this? (with reagents, conditions, mechanism)

Answer 9

• Reagents: sodium cyanide (NaCN) and dilute H2SO4 OR HCN. • Conditions: RTP.
• Mechanism: nucleophilic addition.

• This is useful for increasing the length of the carbon chain.