3.3.6 Organic Analysis Flashcards
Test for alcohols (what you use)
Acidified potassium dichromate
Explain test for alcohols
Acidified potassium dichromate oxidises primary and secondary alcohols but not tertiary alcohols
Primary and secondary will turns from orange to green
Why in test for alcohols colour change from orange to green
Oxidising agent reduces itself
Cr2O7 2- —-> Cr 3+
Problem which acidified potassium dichromate test for alcohols
Primary and secondary both turn green
How to determine from primary and secondary alcohol
Fractional distillation
Then test aldehyde (primary) or ketone (secondary)
Test for Aldehydes and ketones (f)
Fehlings solution + heat water bath
Oxidised aldehydes but not ketones
Aldehyde blue to brick red precipitate
Ketone remains blue
Test for aldehydes and ketones (t)
Tollens reagent + water bath
Make tollens
Aldehyde - silver precipitate (tollens is reduced)
Ketones - no precipitate
How to make tollens reagent
Silver nitrate solution (colourless)
Add few drops NaOH (brown precipitate)
Add dilute ammonia until precipitate dissolves
Why do we use water bath not Bunsen burner when testing for aldehydes and ketones
They are flammable
Test for alkenes and alkanes
Add bromine water
Shake
Alkene- colourless
Alkane - no change
Test for carboxylic acids
Add carbonate ( must be named E.g. sodium hydrogen carbonate)
Will produce bubbles
What carbonate schools use use for carboxylic acid test
Sodium carbonate
How does IR work
Used infrared radiation to increase the vibration energy of the covalent bonds
What is the fingerprint region in IR
Allows use to identify specific molecules
What do addition peak in IR show
Impurities
