Carbonyl Compounds

Question 1

R&C for preparing carbonyl compounds

Answer 1

oxidise 1’ alcohols:
K2Cr2O7(aq), H2SO4(aq), immediate distill

oxidise 2’ alcohols:
KMnO4(aq), H2SO4(aq), heat

Question 2

R&C for oxidation of aldehydes

(ketones can’t oxidise)

Answer 2

K2Cr2O7/KMnO4(aq), H2SO4(aq), heat

Question 3

R&Cf reduction of aldehydes and ketones

Answer 3

LiAlH4 in dry ether/ NaBH4, ethanol, r.t.
or
H2(g), Ni, r.t.

Question 4

R&C nucleophilic addition with HCN

then R&C for acidic hydrolysis & reduction of product

Answer 4

HCN, trace amount of NaCN/NaOH, cold

acidic hydrolysis: H2SO4(aq), heat
-forms COOH
reduction: LiAlH4 in dry ether or H2 & Ni at r.t.
-forms CH2NH2

Question 5

R&C & obs for 2,4 dinitrophenylhydrazine distinguishing test

Answer 5

2,4-dintrophenylhydrazine, r.t.

orange ppt

+ve for both aldehydes and ketones

Question 6

R&C & obs for Tollen’s reagent distinguishing test (Silver Mirror Test)

Answer 6

Tollen’s reagent/ [Ag(NH3)2]+(aq), heat

silver mirror/ grey/black ppt of Ag(s)

-ve result for ketones

Question 7

R&C & obs for Fehling’s solution distinguishing test

Answer 7

Fehling’s solution, heat

brick red ppt of Cu2O(s)

-ve result for aromatic aldehydes & ketones

Question 8

R&C & obs for Iodoform test

Answer 8

I2 in NaOH(aq), heat

pale yellow ppt of CHI3(s)

specific structure required