6.2.5 organic synthesis

Question 1

give the test for carbonyls

Answer 1

add 2,4-DNPH

orange precipitate forms, purify crystals to determine melting point and compare to a database

Question 2

give the test for aldehydes

Answer 2

add Tollen’s reagent and heat or add acidified KCrO7^2-

silver mirror precipitate or yellow to green

Question 3

give the test for carboxylic acids

Answer 3

add sodium carbonate

effervescence and gas forms white ppt in limewater

Question 4

give the test for phenol

Answer 4

add universal indicator

orange as weakly acidic

Question 5

give the test for primary alcohol

Answer 5

add KCrO7^2- and dil H2SO4 and warm gently
then add tollen’s reagent and heat
yellow to green
then silver mirror

Question 6

give the test for secondary alcohols

Answer 6

add KCrO7^2- and dil H2SO4 and warm gently
then add tollen’s reagent and heat
yellow to green
then no observed change

Question 7

give the test for tertiary alcohols

Answer 7

add KCrO7^2- and dil H2SO4 and warm gently

no observed change