Carbonyl Compounds

Question 1

Describe ketones.

Answer 1

Functional group -CCOC-
Name ends in -one
Formed by oxidation of a secondary alcohol

Question 2

Describe aldehydes.

Answer 2

Functional group -CHO
Name ends in -al
Formed by partial oxidation of primary alcohol -> distillation required to obtain pure product

Question 3

Describe the reactions of carbonyl compounds: Reduction: Formation of Alcohols.

Answer 3

Reducing agents: LiAlH4 OR NaBH4 OR H2, Ni/Pt catalyst
Examples:
CH3COCH3 + 2[H] -> CH3CH(OH)CH3 secondary alcohol
CH3CHO + 2[H] -> CH3CH2OH Primary alcohol

Question 4

Describe the reactions of carbonyl compounds: Nucleophilic Addition.

Answer 4

Addition of cyanide ions
Product: Hydroxynitrile
Reagents: HCN, KCN as catalyst
Conditions: Heat
Example: CH3COCH3 -> CH3C(CN)(O-)CH3 -> CH3C(CN)(OH)CH3 + CN (catalyst)

Hydrolysis of hydroxynitrile
CH3C(CN)(OH)CH3 + H2O + HCl (or H2SO4) -> CH3C(COOH)(OH)CH3 + NH4Cl

Question 5

Describe the reactions of carbonyl compounds: Addition-Elimination (condensation)

Answer 5

Also used for to test for carbonyl compounds
Positive test -> Bright yellow / Bright orange precipitate
Brady’s reagent -> 2,4-dinitrophenylhydrazine

Question 6

Describe the reactions of carbonyl compounds: Oxidation

Answer 6

Used to distinguish between ketones and aldehydes.
Will get a positive test for aldehydes.
Tollen’s reagent: Positive test -> grey-silver precipitate
Fehling’s reagent: Positive test -> brick-red precipitate

Question 7

Describe the reactions of carbonyl compounds: Iodoform reaction

Answer 7

Used to test for ketones
Reagents: I2/NaOH OR I2/OH-
Results for positive test is a yellow precipitate.
Positive tests with:
Methyl ketones
Methyl alcohols
Ethanal
Ethanol

Products: Triiodomethane