16.0 Organic analysis Flashcards
(9 cards)
Describe the two chemical methods and observations for distinguishing between alcohols and aldehydes.
Tollen’s reagent: ethanal gives a silver mirror, ethanol no change.
Fehling’s solution: ethanal gives a brick red precipitate, ethanol no change.
What simple chemical test can be used to identify
alkenes? What observations would you make?
Bromine water
Orange to colourless/decolourises in presence of alkene.
What simple chemical test can be used to identify
carboxylic acids? What observations would you make?
Sodium/calcium carbonate
Fizzing/effervescence
What simple chemical test can be used to identify
alcohols? What observations would you make?
Add sodium metal
Fizzing/effervescence
What simple chemical test can be used to distinguish between a primary and tertiary alcohol? What observations would you make?
Acidified potassium dichromate
Primary – orange to green
Tertiary – no change
How can mass spectrometry be used to determine the molecular formula of a compound?
The molecular ion peak is the furthest to the right on the mass spectrum. This indicates the molecular mass.
(Carbon 13 isotopes can cause a 1% abundance to the right of mol ion peak)
How does infra-red spectroscopy distinguish different functional groups in a molecule?
Different bonds absorb IR at characteristic wavenumbers
What is the ‘fingerprint’ region of an infra-red
spectrum and why is useful?
A complex area of the spectrum below 1500cm-1
Why would you expect carbon dioxide, methane, and water vapour to give strong absorbable peaks on an infrared spectrum?
They are greenhouse gases
