Qualitative analysis of organic functional groups

Question 1

Universal indicator paper turns red

Answer 1

Acid - carboxylic acid or phenol

Question 2

Shaken with bromine water, orange brown turns colourless

Answer 2

C=C present

Question 3

Shaken with bromine water, orange brown turns colourless. White ppt. formed

Answer 3

Phenol

Question 4

Warmed with acidified potassium dichromate.

Orange –> Green

Answer 4

Primary/secondary alcohol or aldehyde has been oxidised

Question 5

Warmed with acidified potassium dichromate.

Stays orange

Answer 5

If alcohol, it is a tertiary alcohol (not oxidised)

Question 6

Warmed with Tollens reagent. Silver mirror forms.

Answer 6

Aldehyde

Question 7

Warmed with Tollens reagent. Remains colourless

Answer 7

Ketone

Question 8

Warmed with silver nitrate solution in ethanol. White, cream or yellow ppt.

Answer 8

Chloroalkane
Bromoalkane
Iodoalkane

Question 9

Effervescence when sodium carbonate is added. Gas turns limewater cloudy

Answer 9

Carboxylic acid.

Question 10

Effervescence when magnesium is added. Squeaky pop is heard when lit split is applied to gas.

Answer 10

Carboxylic acid.

Question 11

Add 2,4 DNPH. Orange ppt. formed

Answer 11

Aldehyde or ketone

Question 12

Warm with ethanol and a few drobs of concentrated sulfuric acid. Sweet smell

Answer 12

Ester produced, could be carboxylic acid.