Question

2-pentanone and 3-pentanone can be distinguished by :
(a) Cannizaro's reaction
(b) Aldol condensation
(c) Iodoform reaction
(d) Clemmensen's reduction

Answer 1

Given compounds can be distinguished by - (c) Iodoform reaction

Iodoform reaction is given by compounds having methyl ketone group.

Thus, it can distinguish between the given compounds. 2-pentanone has formula CH3(CH2)2COCH3 and 3-pentanone has formula CH3CH2COCH2CH.

Since methyl group is present in 2-pentanone thus it gives the test. Reaction for test is given below -

CH3(CH2)2COCH3 + I2 + NaOH --> CHI3 + NaI + H2O + CH3CH2CH2COONa.

CHI3 formed is methyl iodide yellow in color. NaI is sodium iodide, H2O is water, I2 represents iodine, NaOH represents sodium hydroxide, CH3CH2CH2COONa is sodium butanoate.

Answer 2

(c) Iodoform reaction

Explanation:

2-pentanone and 3-pentanone can be distinguished by the Iodoform reaction.

2-pentanone gives positive results for Iodoform test while 3-pentanone does not test positive for Iodoform. Iodoform (CHI3) is a yellow solid which precipitates from the reaction mixture.

Chemical formula of 2-pentanone is CH3COCH2CH2CH3.

Chemical formula of 3-pentanone is CH3CH2COCH2CH3.

Iodoform reaction is a chemical reaction in which a methyl ketone is oxidized to a carboxylate by reaction with aqueous HO- and I2.

Option C is the answer.