distinguishing tests (prac) Flashcards
how to test for alkene
to 1 cm3 of sample, add 1-2 drops of Br2 (aq)/(l)/in hexane and shake well.
Br2 (aq): orange solution decolourises
Br2 (l): reddish brown bromine colourises
Br2 in hexane: orange red bromine decolourises
(IN DATA BOOKLET)
to 1cm3 of sample, add 10 drops of H2SO4 (aq) followed by 1 drop of KMnO4. purple KMnO4 decolourises
how to test for halogenoalkanes
1) to 1cm3 of sample in a test tube, add 1cm3 of NaOH (aq)
2) heat in a water bath for 3-5 min
3) cool and acidify with dilute HNO3 before adding 1cm3 of aqueous AgNO3
white ppt: R-Cl
pale cream ppt: R-Br
yellow ppt: R-I (formed fastest)
how to test for primary/secondary alcohols
to 1 cm3 of sample in a test tube, add 10 drops of H2SO4, followed by 1-2 drops of aq KMnO4/K2Cr2O7
heat in water bath for 3-5 min
purple KMnO4 decolourises or orange dichromate turns green
how to test for methyl carbonyl/alcohol thing
to 1 cm3 of deionised water in a test tube, add 1cm3 of the sample solution, 6 drops of NaOH and add iodine solution dropwise until a permanent yellow/orange solution is observed
how to test for carbonyl compounds
to 1cm3 of sample, add 2,4-DNPH dropwise until in excess
orange ppt formed
how to test for aldehyde
to 1cm3 of sample, add 1cm3 of Tollen’s reagent and warm mixture in water bath for 3-5 min
silver mirror formed
how to test for aliphatic aldehyde
to 1cm3 of sample, add 2cm3 of Fehling’s solution and warm mixture in a water bath for 3-5 min
brick red ppt (Cu2O) formed
how to test for phenol
to 1cm3 of sample, add 2 drops of FeCl3 solution
violet colouration observed
or aqueous Br2 dropwise until in excess
orange solution decolourises, white ppt formed
how to test for phenylamine
add Br2 (aq) dropwise until in excess
orange solution decolourises, white ppt formed
how to test for carboxylic acid
Na2CO3
to 1cm3 of sample, add 1cm3 of Na2CO3. Bubble any gas evolved using a delivery tube to 1cm3 of limewater
how to test for acyl chloride
