3.3.6- Organic analysis (PAPER 2) Flashcards
How to test for alkenes?
Shake sample with bromine water
Positive result= orange to colourless.
How to test for alcohols?
Warm alcohol with acidified potassium dichromate.
Primary+ secondary alcohols- orange solution turns green
Tertiary alcohols- solution stays orange as there is no reaction.
How to test for carboxylic acids?
Add sodium carbonate solution/solid and
bubble the gas produced through limewater
Positive result= will cause limewater to go cloudy
How to test for aldehydes?
Fehling’s solution
-warm sample with fehling’s solution
-positive result= clear blue to red precipitate
-no reaction with ketones
Tollens’ reagent
-add silver nitrate solution
-add dilute sodium hydroxide
-add dilute ammonia solution (Tollens’ reagent)
-positive result will form a silver mirror inside test tube
-no reaction with ketones
How to test for halogenalkanes?
Warm sample with aqueous sodium hydroxide, acidify with nitric acid, add silver nitrate.
Precipitate formed= Cl white, Br cream
I yellow.
What is a high resolution mass spectrometer?
Records mass to a much higher resolution ( eg 0.0001)
Can differentiate between molecules of the same mr based on tiny differences in ar.
Precise relative molecular mass measured.
How does infrared spectroscopy work?
Beam of infrared radiation is passed through sample in the form of EM waves. Covalent bonds in the molecule absorb specific frequencies of IR. Bonds in a molecule absorbed IR at different wave numbers.
What is the fingerprint region?
The peaks below 1500cm
Can compare to known spectra to identify a compound.
Link between infrared radiation and the atmosphere.
Some molecules in the atmosphere absorb IR and contribute to global warming.
Natural frequency of bond vibrations in molecules like CO2 coincides with frequency of the infrared radiation- this occurs when sample is placed in infrared spectrometer.
