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Methods (Aldehydes + Ketones) - Coggle Diagram
Methods
(Aldehydes + Ketones)
Confirmation of Product
A+K
REACTS
with
2,4-dinitrophenylhydrazine
forms orange ppt
product
FILTERED
purified by
RECRYSTALLISATION
crystals
DRIED
determine
MELTING
point
COMPARE
with table of melting points
of 2,4-dinitrophenylhydrazones
identify unknown organic compounds
by preparing derivative
Laboratory Preparation of
2,4-dinitrophenylhydrazones
place 5cm3 of 2,4-DNPH
solution
in suitable container (
test tube
)
add some
DROPS
test liquid (propanal)/test solid dissolved in ethanol
if crystals
don't form
add some
dilute SULFURIC ACID
WARM
mixture in water bath
COOL
mixture in iced water
(ensures solid does not dissolve)
FILTER
off crystals using
suction filtration
RECRYSTALLISE
(using ethanol as solvent)
dry hydrazone crystals
in low temperature oven
or desiccator
DETRMINE
melting point
(compare MPs of hydrazones
in data table)
Recrystallisation
DISSOLVE
impure crystals in
minimum amount/volume of
HOT solvent
FILTER
solution whilst hot by gravity filtration, using hot
to
remove insoluble
impurities
COOL
filtrate + allow
to crystallise
impurities are left
in the solution
FILTER
off crystals
DRY
crystals
between filter paper
cool oven (low temp)
desiccator
Suction Filtration
benefits
much faster than gravity
place
FILTER PAPER
in
Buchner funnel
place Buchner funnel
in
BUCHNER FLASK
attach flask to
SUCTION PUMP
+
suck air through flask
diagram
Melting Points
place some solid in
CAPILLARY TUBE
(sealed @ one end)
HEAT
slowly
(using melting point apparatus)
RECORD
temp @ which solid
starts + finishes melting
REPEAT
+ average
COMPARE
temps
in data book
effect of impurities on MP
broad range
lower
pure solid
solid which melts
within range of 1-2°C