Question

02:53:33
054
An organic compound shows the following characteristics reaction/tests:
1) +ve: 2,4-DNP
ii) -ve: Schiff's
m) -ve: Tollens
iv)-ve: Fehillings
v) +ve: NaHSO3
vi) + ve: lodoform
Which compound is fit for these facts?
Acetone​

Answer 1

Djdnhznxjxnxhxnxcnhn ddx

Answer 2

Answer:

Acetone shows the following characteristic reactions.

Explanation:

(i)Reaction with 2, 4 dinitrophenylhydrazine:

2, 4 dinitrophenylhydrazine is Brady's reagent. Both aldehydes and ketones react with 2, 4 dinitrophenylhydrazine to form a yellow or orange precipitate.

Acetone reacts with 2, 4 dinitrophenylhydrazine to form 2, 4 dinitrophenylhydrazone.

(ii)Reaction with Schiff's reagent(Schiff's test):

Schiff's reagent is a dilute solution of the dye rosaniline hydrochloride in water whose pink or red colour is discharged by passing sulphur dioxide. When an aldehyde is treated with Schiff's reagent, the pink colour of the dye is restored.

Aldehyde + Schiff's reagent(colourless) → Pink colour

The restoration of the pink colour of Schiff's reagent is called Schiff's test. Ketones do not respond to this test.

Acetone, however, restores the colour of Schiff's reagent but very slowly.

(iii)Reaction with Tollen's reagent:

Tollen's reagent is an ammoniacal solution of silver nitrate.

When an aldehyde is warmed with Tollen's reagent, it gets oxidised to the corresponding carboxylic acid which combines with ammonia to form an ammonium salt, while Tollen's reagent, in turn, gets reduced to metallic silver. The metallic silver deposits on the inner walls of the test tube to form a silver mirror. Ketones do not give this test.

Thus, acetone gives negative Schiff's test.

(iii)Reaction with Fehling's solution:

Fehling's solution is an alkaline solution containing cupric ions complexed with tartarate ions and is prepared by adding Fehling solution A to Fehlings solution B.

When aliphatic aldehyde is warmed with Fehling's solution, the aldehyde gets oxidised to the corresponding carboxylic acid, while the cupric ions get reduced to cuprous ions, which get precipitated in the form of red precipitate of cuprous oxide.

Thus, acetone shows negative Fehlings test.

(v)Reaction with NaHSO₃:

Aldehydes and ketones react with NaHSO₃ to form aldehyde and ketone bisulphite. Thus, both give a positive test with sodium bisulphite. Acetone on reaction with sodium bisulphite forms acetone sodium bisulphite as the end product.

(vi)Iodoform reaction:

Aldehydes and ketones containing CH₃CO- group can also be oxidised with sodium hypohalite to give a haloform and salt of carboxylic acid. The reaction is commonly known as the haloform reaction. Among aldehydes, the haloform reaction is given by only acetaldehyde because other aldehydes do not possess CH₃CO- group.

When the reaction is carried out with sodiumhypoiodite, the iodoform formed in the reaction is obtained as a bright yellow precipitate. This is used as a test for methyl ketones and is known as the iodoform reaction. Among ketones, the reaction is given by almost all methyl ketones.

Acetone gives a positive iodoform reaction and the reaction is as follows.

CH₃COCH₃ + 3I₂ + 4NaOH → CHI₃ + CH₃CHCOONa + 3NaI + H₂O