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 colorless

characterstic pungent

Ignition test

acetophenone

benzaldehyde

Chloral hydrate

aceton

acetaldehyde

formaldehyde

inflammable Non inflammab

le

inflammable

luminous - Nonluminous

smoky - No smoky

volatilization melting volatilization

No change

No change

No residue

Acid base character

acetophenone

benzaldehyde

Chloral hydera

te

aceton

acetaldehyde

formaldehyde

immiscible soluble miscible H2O

Not done No change

No 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 test

No reaction No reaction Crimson red color

Salicylic 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 test

Yellow 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