3.3.6 Organic Analysis Flashcards
What is the test for an alkene? Result?
Shake with bromine water, orange to colourless solution.
What is the test for an halogenoalkane? Result?
Add NaOH(aq) and warm, acidify with HNO3, add AgNO3(aq). White solid (chloroalkane), cream solid (bromoalkane), yellow solid (iodoalkane).
What is the test for an alcohol? Result?
Add acidified potassium dichromate (VI) solution (Kr2Cr2O7). Orange colour turns green with primary or secondary alcohols (also with aldehydes).
What is the test for an aldehyde? Result?
Warm with Fehling’s solution OR warm with Tollen’s reagent. Blue solution turns to brick red precipitate OR forms a silver mirror.
What is the test for a carboxylic acid? Result?
Add sodium hydrogen carbonate(aq) (NaHCO3). CO2 given off (effervescence).
Why do we take accurate masses of atoms to 4 d.p?
Because some compounds have the same Mr (eg. C3H8 and CH3CHO both have an Mr of 44).
How does infrared spectroscopy work?
Shine a range of IR frequencies, one at a time through an organic compound.
Infrared energy is absorbed by a molecule causing bond stretching and bond bending.
This produces peaks at certain wavenumbers, corresponding to different functional groups.
C-H is the functional group of what?
Alkanes/alkenes/aldehydes.
C=C is the functional group of what?
Alkenes.
O-H is the functional group of what?
Alcohols/carboxylix acids.
N-H is the functional group of what?
Amines.
C=O is the functional group of what?
Aldehydes/ketones.
Where is the fingerprint region found?
Area below 1500 cm^-1 in an infrared spectrum.
What does the fingerprint region contain, how are these formed?
Many peaks caused by complex vibrations of the whole molecule.
What do we do with the fingerprint region?
Use a database of known compounds to compare with.
