Functional Group Tests and Observations

Question 1

Alkene (C=C)

Answer 1

Test: add bromine water
Observation: bromine water decolourises

Question 2

Carboxylic acids (R-COOH)

Answer 2

Test: add NaHCO3(aq) or Na2CO3(aq) and warm if necessary
Observation: bubbles of gas

Question 3

Phenol (C6H6O)

Answer 3

Test: add bromine water
Observation: bromine immediately decolourises, white ppt forms

Question 4

1° Alcohol (R-C-OH)

Answer 4

Test: Acidified potassium dichromate (K2Cr2O7)
Observation: Orange to green

Question 5

2° Alcohol (RR’C-OH)

Answer 5

Test: Acidified potassium dichromate (K2Cr2O7)
Observation: Orange to green

Question 6

Carbonyl group

Answer 6

Test: Add 2,4-dinitrophenylhydrazine
Observation: Orange Precipitate

Question 7

Ketones, 2°/3° Alcohols with CH3

Answer 7

Test: Add an alkaline solution of iodine and warm
Observation: Yellow precipitate forms

Question 8

Steps for confirmatory test for halogenoalkanes?

Answer 8

1. Warm with NaOH
2. Then add dilute HNO3
3. Few drops of AgNO3 (aq)

Question 9

Observations for R-Cl? Further confirmatory test?

Answer 9

1. White precipitate

2. Insoluble in dilute NH3 (aq)

Question 10

Observations for R-Br? Further confirmatory test?

Answer 10

1. Cream precipitate

2. Insoluble in dilute NH3 (aq), soluble in concentrated in NH3 (aq)

Question 11

Hydroxy (-OH)

Answer 11

Test: Add PCl5
Observation: Misty fumes

Question 12

Methyl carbonyl or methyl alcohol?

Answer 12

1. Test : alkaline solution of iodine, warm

2. Observation : Yellow precipitate forms