carbonyl compounds and carboxylic acids

Question 1

green box: testing for carboyl groups in aldehydes and ketones

Answer 1

1. • 5cm depth 2,4 DNP -> clean test tube
2. dropping pipette -> 3 drops-> unknown compound
3. no crystals form-> + drops of sulfuric acid
4. yelllow/ orange precipitate= presence of aldheyde/ketone

Question 2

testing for adheyde group with tollens reagent

Answer 2

1. • 3 cm depth aqeous silver nitrate-> clean test tube
2. • aqeous sodium hydroxide-> silver nitrate until brown precip of silver oxide forms
3. • dilute ammonia solution until brown precip clears –> colourless solution (Tollens reagent)
4. • 2cm depth unknown solution –> cean test tube
5. • equal volume of tollens reagent
6. leave test tube in beaker of warm water @ 50 degrees celscius for 10-15 mins; observe whether silver mirror formed or not

Question 3

identifying aldheyde and ketone by melting point

Answer 3

2,4 dnp precip analysed

1. yellow/ orange solid filtered from solution
2. solid recrystallised-> pure crystals
3. MP if 2,4 DNP measured + recorded
4. MP compared to data base of carbonyl compounds

Question 4

How to distinguish a carboxylci acid from a phenol

Answer 4

react with carbonate- carb acids are only organic compounds acidic enough to react with carbonate

Question 5

making ethyl propanoate

Answer 5

1. • 2cm3 of ehtanpl and equal vol of propanoic –> boiling tube
2. • drops of conc h2so4 to mixture
3. place boiling tube in beaker of hot water @ 80 degrees celscius
4. • contents of boiling tube–> beaker of aq sodium carbonate ( this is a weak base and neutralises acids in mixture , also removed smell of any carb acid that hasnt reacted , thus easier to detect smell of ester )
5. oily drops of ester would be present floating on the water , and you can smell it