Organic Analysis Flashcards
Test for alkenes
Bromine water
Orange to colourless
Test for primary or secondary alcohols
Acidified potassium dichromate (K2Cr2O7)
Orange to green
Test for Aldehydes
Warm with Tollens’s reagent
Silver mirror forms
OR
Warm with Fehling’s solution
Blue solution to brick red precipitate
Test for carboxylic acids
Add sodium carbonate (Na2CO3)
Effervescence
Why can multiple peaks appear on the mass spectrum?
Because when a molecule is analysed in a mass spectrometer, it can break up into smaller molecules called fragments. These all have different masses so different peaks can appear
State the meaning of the term ‘molecular ion’ peak
Has m/z equal to Mr of molecule
(peak with largest m/z value)
Imprecise (low resolution) mass spectrometry data is measured to what?
1 decimal place
High resolution mass spectrometry data is measured to what?
5 decimal places
Why can’t a mass spectrometer which measures m/z ratios to 1 decimal place tell the difference between C10H16O4 and C11H4O4?
They have the same molecular mass to 1 decimal place
Why can’t high resolution mass spectrometry tell the difference between propan-1-ol and propan-2-ol?
They have the same molecular formula so their molecular mass will be exactly the same
Why does C have a relative molecular mass of 12.00000?
By definition 12Carbon is the standard reference
How does infrared spectroscopy work?
A beam of IR radiation is passed through a sample containing a molecule
Infrared energy is absorbed by bonds in the molecule which makes the bonds vibrate
The bond vibrate at the same frequency as the infrared energy
What is the fingerprint region?
The area of the spectrum 1500cm-1 and below
How can mass spectrometry be used to confirm that a compound is definitely ethyl butanoate?
Compare with a known spectrum from a database, it should be an exact match
