Aldehydes and ketons
Formaldehyde.Acetaldehyde.Chloral hydrate.Benzaldehyde.Aceton.Acetophenone.
It contains variety of chemical compound including benzoate, ceosol,, benzaldehyde, y-terpineol, nerolidol, isohytol, phytol and acetic acid
Chloral Hydrate is a sedative/hypnotic drug used to treat insomnia
Aldehydes and ketons
acetophenone
aceton benzaldehyde
Chloral hydrate
acetaldehyde
formaldehyde
aromatic aliphatic
aromatic aliphatic
True liq. oily True liq. mobile
True liq. oily Solid micro
crystalline
True liq. mobile
Liq. mobile solution
colorless white colorlesscharacterstic pungent
Ignition test
acetophenone
benzaldehyde
Chloral hydrate
aceton
acetaldehyde
formaldehyde
inflammable Non inflammab
le
inflammable
luminous - Nonluminoussmoky - No smoky
volatilization melting volatilization
No changeNo changeNo residue
Acid base character
acetophenone
benzaldehyde
Chloral hydera
te
aceton
acetaldehyde
formaldehyde
immiscible soluble miscible H2ONot done No
changeNo chang L.P
immiscible
Not done
Dil HCl
immiscible 10% NaOH
? H2SO4
All neutral
Preliminary test
Soda lime test:
Only for solid Few chlorahydrate +few soda lime in mortor →sweety odor of chloroform odor
Do not smell
30%NaOH: It is done for compound with no ᾳ hydrogen like
aromatic aldehyde( bezaldehyde) and formaldehyde:
In this case Called self oxidation –reduction reaction .
Called cannizzaro᾿s reaction.
Difficult to be done ( need time and high temp.)
Benzyl alc.+
benzoic acid
Methanol +
formic acid
in case of compound with ᾳ hydrogen like acteldehyde.
Called aldol condensation: Dil acetaldehyde + xss 30% NaOH →yellow
resin of bad apple odor B-hydroxy aldehyde
Fecl3:All no reaction.
Conc. H2SO4: no reaction with all except with chlorahydrate. Few chlorahydrate + Conc. H2SO4 on cold
→sepration of oily layer of chloral
Chlorahydrate: chlor. +30%NaOH on cold but some times need to warm → sweety odor of chloroform +oily droplet.
Aceton and acetophenone: no reaction.
General test
2,4 dinitrophenyl hydrazine test:
silver mirror test (tollen᾿s reagent test or ammonical silver nitrate test:
fehling reagent test or fehling reduction test
2,4 dinitrophenyl hydrazine test
1 ml of ald. Or keton + 3 dps of reagent Aor B then shaking
Reagent A
For aldehyde and keton miscible in
H2O
Reagent B
For aldehyde and keton immiscible in
H2O
Formaldehyde acetaldehyde Chlorahydrate
aceton
Benzaldehyde
acetophenone
formaldehyde: yellow ppt.
Acetaldehyde: yellow orange ppt.
Chlorahydrate: no reaction ( yellow color)
Aceton: orange yellow ppt.
Benzaldehyde: orange ppt.
Acetophenone: orange ppt.
silver mirror test (tollen᾿s reagent test or (ammonical silver nitrate test
tollen᾿s reagent: 1-5 ml of silver nbitrate + 1 dp 10% NaOH →black ppt. of Ag2O (SLIVER OXIDE) + dil. NH4OH until clear solution obtained
1 ml tollen᾿s reagent + 1ml aldehydes or ketons heat on water bath for 10 minutes then cool on rack
Formaldehyde and acetaldehyde: rapidly give silver mirror.
Chlorahydrate and benzaldehyde: silver mirror after longer time on the water bath.
Aceton and acetophenone : no reaction..
fehling reagent test or fehling reduction test
Mix equal amount of fehling A + B to give blue color of cupric ion
Few aldehydes or ketons + few Na2CO3 + fehling mix and put it in water bath
yellow or red ppt. of cuprous oxide
Formaldehyde actaldehyde : rapidly change in color.
Chlorahydrat and benzaldehyde: take longer time to change the color.
Aceton and acetophenone: no reaction
Specific test
benzaldehyde acetaldehyde formaldehyde Aldehydes testNo reaction No reaction Crimson red
colorSalicylic acid test:Alds +salic. a. +Conc H2SO4
No rection Yellow resin(dil. Acetaldehyde)
-ve result (yellow color)
Iodoform test:Alds.+ 10% NaOH* +Xss iodine (wait)
No reaction Red color(dil. With water to see it)Clear with light
No red color Na nitroprusside test: alds.+ Na nitro. +10%NaOH
Needle crystal of benzoic acid
- - Auto oxidation test:
acetophenone aceton Ketones testYellow ppt. Yellow ppt. Iodoform test:Red color Red color Na nitroprusside test:
Violet color in organic layer
(dissolve acetophenone in
ethanol)
Deep violet color slowly fade
Meta dinitro benzen test:Kets. + meta dinitro benzene+ Xss 10% NaOH (Shake)
chlorahydrate
Soda lime test: sweety odor of chloroform.
Conc. H2SO4: sepration of chloral layer.
30% NaOH: oily droplet and chloroform odor
IR location
C-H stretching band of aliphatic under 3000 cm -1.
C-H stretching band of aromatic above 3000 cm-1.
Carbonyl group stretching band of aldehyde at 1725 cm-1.
Carbonyl group stretching band of ketone at 1715 cm-1
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