ALDEHYDES & KETONESALDEHYDES & KETONES

R C H

O O

R C R

StructureStructure StructureStructure

Formaldehyde Acetone

Acetaldehyde Acetophenone

Chlorahydrate

Benzaldehyde

CH3

OH3C CH3

O

H

O

CCl3CH

OH

OH

H3C H

O

H H

OHCHO or

Aldehydes Aldehydes ketonesketones

State Color Odor

Physical propertiesPhysical properties

Formaldehyde

Acetaldehyde

Acetone

Chlorahydrate

Benzaldehyde

Acetophenone

Liquid, mobile, solution

Liquid, mobile, true

Liquid, mobile, true

Solid, crystalline

Liquid, oily, true

Liquid, oily, true

Colorless

Colorless

Colorless

Colorless

Colorless

White

Characteristic odor

Characteristic odor

Characteristic odor

Bitter almond odor

Pungent

Pungent

Ignition testIgnition testInflammability Change in

appearanceChange in color flame

Change in color

Residue Comment

Formaldehyde

Acetaldehyde

Acetone

Chlorahydrate

Benzaldehyde

Acetophenone

Inflammable, non luminous,

non smoky

Inflammable, luminous,

smoky

Non inflammable

Volatilization

Volatilization

Melting

No change for all

Noresiduefor all

Nochange for all Aliphatic

Aliphatic

Aliphatic

Aliphatic

Aromatic

Aromatic

Miscibility & SolubilityMiscibility & SolubilityH2O Dil. HCl 10% NaOH Conc.

H2SO4

Litmus paper

Formaldehyde

Acetaldehyde

Acetone

Chlorahydrate

Benzaldehyde

Acetophenone

Miscible //

Miscible //

no change

no change

no change

no change

Miscible //

Soluble //

Immiscible in all

Immiscible in all

CommentComment All the compounds are neutralAll the compounds are neutral

Preliminary testsPreliminary testsFormal. Acetal. Chlora. Benzal. Acetone Acetoph.

Soda lime test (for solid only)

30% NaOH

On cold

On hot

Sweety odor of chloroform odor

It is done for compound with no α hydrogen (( Self oxidation – reduction reaction))

Called Cannizzaro’s reactionAll aromatic aldehyde & only formaldehyde

goes cannizzaro’s reactionNo reaction

Not doneNot done

On hot

Dil. acetal.+ xss 30%NaOH

Yellow resin + bad apple odor ((Called aldo condensation))

No α hydrogen

Cannizzaro’s reaction

No reaction

No reaction

No reactionUndergoes cannizzaro’s reactionMethanol + formic acid

Sweety odor of chloroform odor + droplets of oil

White ppt((it is difficult to be done))

[Difficult to be done]

C

O

CHhydrogen

CHO

30% NaOH

COOH

CH2OH Conc HCl

(Acetone & Acetoph.)

(Acetone & Acetoph.)

Preliminary testsPreliminary testsFormal. Acetal. Chlora. Benzal. Acetone Acetoph.

FeCl3

On cold

On hot

Conc. H2SO4

On cold

On hot No reaction

No reaction

No reaction

No reaction

No reaction for all

No reaction for all

Separation of an oily layer of Chloral

Not done

General test of class:General test of class:

Reagent AReagent A

For formaldehyde & ketones miscible in H2O

For aliphatic{Formaldehyde, Acetaldehyde,

Chlorahydrate, Acetone}

Reagent BReagent B

For aldehyde & ketones immiscible in H2O

For aromatic{Benzaldehyde & Acetophenone}

Aldehyde or ketones + 3 drops from reagent A or B shaking

Yellow ppt

Yellow– orange ppt

No reaction

Orange ppt

Orange– yellow ppt

Orange ppt

Formal. Acetal. Chlora. Benzal. Acetone Acetoph.

1] 2, 4 – dinitrophenyl hydrazine test: 1] 2, 4 – dinitrophenyl hydrazine test:

General test of class:General test of class:

2] Silver mirror test = Tollen’s reagent test = Ammonical silver 2] Silver mirror test = Tollen’s reagent test = Ammonical silver nitrate test: nitrate test:

Few ml of silver nitrate + 1 drop 10% NaOH

Called Tollen’s reagent

Black ppt of Ag2O + dil. NH4OH ((until clear solution obtained)) (1)

1ml of Tollen’s reagent + 1ml aldehyde or ketones [ heat on water bath 10 min.] cool on the rack(2)

NOTE:NOTE: Reagent 1st then aldehyde or ketones

Formal. Acetal. Chlora. Benzal. Acetone Acetoph.

No reactionSilver mirror after longer time on the

water bath

Rapidly gives silver mirror

General test of class:General test of class:

3] Fehling reagent test = Fehling reduction test:3] Fehling reagent test = Fehling reduction test:

Fehling AFehling A Fehling BFehling 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)

(2) heat on water bath

Formal. Acetaldehyde Chlora. Benzaldehyde Acetone Acetophenone

Rapidly change in color Change in color take longer time

No reaction