RP 6 - organic

what is RP 6

tests for alcohol, aldehyde, alkene and carboxylic acid

test for alcohol (metal)

1. add piece of metal Na to alcohol

2. produces H2 shown by squeaky pop test

3. dispose XS Na using ethanol - if comes in contact with water there is a serious fire risk

test for alcohol (potassium dichromate)

1. primary and secondary will reduce it from orange dichromate (VI) to green chromium (III) ions

2. remains orange if tertiary

test for aldehyde (fehlings)

1. mix equal volumes of fehlings solution A and B with resultant reagent being a clear dark blue solution

2. add drops to test tube and anti bumping granules

3. add aldehyde

4. warm gently for 2 mins in beaker of hot water - gradually bring beaker to boiling and maintain temp

5. lift test tube out and allow to stand for few mins

6. brick red ppt formed

test for alkene

1. add bromine to alkene (1cm3 : 2 drops)

2. shake contents vigorously from side to side

3. bromine water decolourised from orange if alkene present

test for carboxylic acid

1. place spatula of Na2CO3 in test tube and add dilute ethanoic acid using pipette

2. collect gas produced and bubble through limewater

3. turns cloudy as CO2 produced

problems with phenols

also acidic but are not sufficiently acidic to react with carbonates

test for haloalkane

1. use teat pipette to add 1-bromobutane to NaOH to test tubes (nucleophilic sub)

2. warm contents for few mins in beaker filled with hot water approx 60 degrees

3. acidify by adding HNO3 and then AgNO3

4. AgBr ppt forms

what does HNO3 do

removes carbonate and hydroxide impurities which would form ppts