WM Flashcards
aldehyde general formula
RCHO
ketone general formula
RCOR’
carboxylic acid general formula
RCOOH
acid anhydride general formula
RCOOCOR’
ether general formula
ROR’
ester general formula
RCOOR’
primary, secondary and tertiary alcohols
. primary - OH group attached to carbon that is bonded to one R group
. secondary - OH group attached to carbon that is bonded to 2 R groups
. tertiary - OH group that is attached to 3 R groups
what is the reagent used to oxidise an alcohol
potassium dichromate (K2CR2O7)
what colour does the dichromate turn from and to when used to oxidise an alcohol
solution goes from orange to green
how do you extract an aldehyde from the oxidation of a primary alcohol
use distillation. aldehyde has lower boiling point than alcohol so will evaporate first
how do you form a carboxylic acid from a primary alcohol
heat under reflux and use excess oxidising agent
why, when heating under reflux, does the aldehyde not get removed?
aldehyde is evaporated then condenses and falls back down into flask
how is an ester formed
by reacting an alcohol with a carboxylic acid or an acid anhydride
what is a phenol
OH group (hydroxyl group) attached to a benzene ring
test for phenols
add iron (III) chloride to solution. if phenol is present a purple colour should form
how does reflux work
strong heating and you won’t lose volatile (can readily change from solid/liquid form to vapour) reactants and products. volatile compounds will evaporate and condense back into flask.
when is distillation performed
when you are trying to separate two substances with different boiling points
how does recrystallisation work
you do this when you want to purify solids.
1. add just enough hot solvent to dissolve impure solid.
2. crystals should begin to form, let them cool.
3. filter these crystals to get your solid purified crystals. wash these with very cold solvent and dry them off.
what is the mobile phase and stationary phase in TLC
mobile phase = solvent
stationary phase = paper
how can colourless compounds be seen in TLC
using iodine or fluorescent dyes and uv light.
how can you spot the spots in TLC using iodine
place chromatogram in a sealed jar containing iodine crystals. the iodine vapour will stick to the chemicals and turn them purple.
how can you spot the spots using a fluorescent dye
add dye to paper. colourless spots will block any glow from dye and you can then draw around these spots to see them more clearly.
