ALDEHYDES & KETONES
It contains benzaldehyde, and acetic acid
Chloral Hydrate is a sedative/hypnotic drug used to
treat insomnia
Structure
Formaldehyde
HCHO
Acetaldehyde
or
Structure
Acetone
Acetophenone
Chlorahydrate
Benzaldehyde
Aldehydes
ketones
Physical properties
State
Color
Odor
Formaldehyde
Liquid, mobile, solution Colorless
Pungent
Acetaldehyde
Liquid, mobile, true
Colorless
Pungent
Acetone
Liquid, mobile, true
Colorless
Characteristic odor
Solid, microcrystalline
White
Characteristic odor
Benzaldehyde
Liquid, oily, true
Colorless
Characteristic odor
Acetophenone
Liquid, oily, true
Colorless
Characteristic odor
Chlorahydrate
Ignition test
Inflammability
Change in
appearance
Change
in color
Residu
e
Formaldehyde
Acetaldehyde
Acetone
Comment
Aliphatic
Inflammable,
non luminous, Volatilization
non smoky
Chlorahydrate
Non
inflammable
Melting
Aliphatic
No
change
for all
No
residue
for all
Aliphatic
Aliphatic
Benzaldehyde
Aromatic
Acetophenone
Inflammable,
luminous,
smoky
Volatilization
Aromatic
Miscibility & Solubility
H2O
Dil. HCl
10% NaOH
Litmus paper
Formaldehyde
Acetaldehyde
Acetone
Chlorahydrate
Benzaldehyde
Acetophenone
Comment
Miscible // no change
Miscible // no change
Miscible // no change
Soluble //
no change
Immiscible in all
Immiscible in all
All the compounds are neutral
Preliminary tests
Formal.
Soda lime test
(for solid only)
Acetal.
Chlora.
Benzal.
Acetone
Acetoph.
Sweety odor of
chloroform odor
30% NaOH
It is done for compound with no α hydrogen
(( Self oxidation – reduction reaction))
Called Cannizzaro’s reaction On hot [Difficult to be done]
All aromatic aldehyde & only formaldehyde goes cannizzaro’s reaction
On cold
No reaction
Dil. acetal.+ xss
30%NaOH
Yellow resin + bad
apple odor ((Called
aldo condensation))
On hot
Undergoes
cannizzaro’s
reaction
Methanol +
formic acid
Not done
Sweety odor No α hydrogen No reaction
of chloroform
odor +
Cannizzaro’s (Acetone &
Acetoph.)
droplets of oil reaction
No reaction
Not done
No reaction
White ppt
((it is difficult (Acetone &
to be done))
Acetoph.)
Preliminary tests
Formal. Acetal.
Chlora.
Benzal.
Acetone
Acetoph.
FeCl3
No reaction for all
On cold
On hot
No reaction for all
Conc. H2SO4
On cold
No reaction
Separation of an oily
layer of Chloral
No reaction
On hot
No reaction
Not done
No reaction
General test of class:
1] 2, 4 – dinitrophenyl hydrazine test:
Reagent A
Reagent B
For formaldehyde & ketones miscible in
H2O
For aldehyde & ketones immiscible in H2O
For aromatic
For aliphatic
{Benzaldehyde & Acetophenone}
{Formaldehyde, Acetaldehyde,
Chlorahydrate, Acetone}
Aldehyde or ketones + 3 drops from reagent A or B shaking
Formal.
Yellow
ppt
Acetal.
Chlora.
Benzal.
Acetone
Acetoph.
Yellow– orange
No
ppt
reaction
Orange
ppt
Orange– yellow
ppt
Orange
ppt
General test of class:
2] Silver mirror test = Tollen’s reagent test = Ammonical silver
nitrate test:
Few ml of silver nitrate + 1 drop 10% NaOH
Black ppt of Ag2O + dil. NH4OH
((until clear solution obtained))
(1)
Called Tollen’s reagent
1ml of Tollen’s reagent + 1ml aldehyde or ketones
(2)
[ heat on water bath 10
min.] cool on the rack
NOTE: Reagent 1st then aldehyde or ketones
Formal.
Acetal.
Rapidly gives silver
mirror
Chlora.
Benzal.
Silver mirror after
longer time on the
water bath
Acetone
Acetoph.
No reaction
General test of class:
3] Fehling reagent test = Fehling reduction test:
Fehling A
Fehling B
In test tube mix equal amount of Fehling A + Fehling B
Blue color
(1)
In test tube few aldehyde or ketones + few Na2CO3 + (Fehling A + B)
heat on water bath
(2)
Formal. Acetaldehyde Chlora. Benzaldehyde Acetone
Rapidly change in color
Change in color take
longer time
Acetophenone
No reaction