WM - Identification of Functional Groups (test-tube reactions)

Question 1

functional group = alkene

Answer 1

reagent - bromine water
result - orange to colourless

Question 2

functional group = aldehyde

Answer 2

reagent - Fehlings solution
result - blue solution to red precipitate

Question 3

functional group = aldehyde

Answer 3

reagent - Tollens reagent
result - silver mirror formed

Question 4

functional group = carboxylic acid

Answer 4

reagent - sodium carbonate
result - effervescence of co2 evolved

Question 5

functional group = 1* 2* alcohol and aldehyde

Answer 5

reagent - sodium dichromate and sulphuric acid
result - orange to green colour change

Question 6

functional group = chlorophyll alkane

Answer 6

reagent - warm with silver nitrate
result - slow formation of white precipitate of AgCl

Question 7

Tollens reagent reaction?
(reagent + conditions + reaction + observation)

Answer 7

reagent - formed by mixing aqueous ammonia and silver nitrate
[Ag(NH3)2]* complex formed
conditions - heat gently
reaction - ALDEHYDES only are oxidised into carboxylic acids
silver ions are reduced to silver rations
observations - with ALDEHYDES a silver mirror is formed coating inside of test tube. for KETONES no change

Question 8

Fehling’s solution reaction?
(reagent + conditions + reaction + observation)

Answer 8

reagent - fehlings solution containing blue Cu2+ ions
conditions - heat gently
reaction - ALDEHYDES are oxidised by the solution into a carboxylic acid
copper (II) ions are reduced to copper (I) oxide
observation - ALDEHYDES blue Cu2+ change to red precipitate of Cu2O. KETONES do not react