Chem 4 AQA Identifying functional groups using simple test-tube reactions

all the tests you need to know parrot fashion 

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  • Created by: Ella Shaw
  • Created on: 12-06-12 10:37

Alkenes

Test- add bromine water

Result- Orange-brown solution to colourless solution

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Haloalkanes

Test- Haloalkane in ethanol warmed with aqueous silver nitrate solution. OR Haloalkane in ethanol warmed with aqueous sodium hydroxide and then neutralised using aqueous nitric acid, followed by silver nitrate. 

Chloro- Colour of silver precipitate: White

           - After adding dilute ammonia: dissolves to produce a colourless solution

Bromo- Colour of silver precipitate: Cream

           - After adding dilute ammonie: precipitate is insoluble

           - After adding concentrated ammonia: precipitate dissolves to produce a                  colourless solution

Iodo- Colour of silver precipitate: Yellow

       - After adding dilute ammonia: precipitate is insoluble

       - After adding concentrated ammonia: precipitate is insoluble

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Carboxylic acids

Test- Add NaHCO3

Result- Bubbles of gas (CO2) which turn limewater cloudy

Test- Universal indicator

Result- Orange (approx pH3) 

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Aldehydes and Ketones

Test- Tollen's test (contains [Ag(NH3)2]+) 

Result- with aldehyde: Silver mirror forms

          - with ketone: no change

Test- Fehling's test (contains Cu2+ ions) 

Result- with adehyde: brick red precipitate forms

          - with ketone: no change 

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Alcohols

Test- heat alcohol with oxidising agent eg acidified (sulfuric acid) Potassium Dichromate OR acidified (sulfuric acid) potassium manganate

Primary Alcohol- With potassium dichromate: Orange solution to green solution

                         - With potassium manganate: Purple solution to colourless solution

Secondary alcohol- With potassium dichromate: orange solution to green solution

                             - With potassium managanate: purple solution to colourless                                       solution

Tertiary alcohol- With potassium dichromate: no change

                        - with potassium manganate: no change

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Acyl Chlorides

Test- add silver nitrate (AgNO3)

Result- vigorous reaction, fumes given off instantly. White precipitate of AgCl forms

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