Question

The compound which can be used to prepare iodoform is:
A.Methyl iodide
B.Acetone
C.Propionaldehyde
D.Acetic acid

Answer 1

Iodoform or triiodomethane is an organic compound with the formula ${\text{CH}}{{\text{I}}_{\text{3}}}$ and it is analogous to chloroform.

Complete step by step answer:
Iodoform can be prepared by the iodoform reaction. The iodoform reaction refers to the chemical reaction in which a methyl ketone is subjected to oxidation by allowing it to react with aqueous sodium hydroxide $\left( {{\text{NaOH}}} \right)$ and iodine $\left( {{{\text{I}}_{\text{2}}}} \right)$ to form a carboxylate. The iodoform reaction also produces a yellow solid which precipitates from the mixture. This yellow solid produced from the iodoform reaction is called iodoform. Since acetone is a methyl ketone, it can be used to prepare iodoform.

So ,option B is correct.

The other three options do not define a methyl ketone and so they are incorrect.

Additional information: (1) Iodoform can also be prepared from some other organic compounds like ethanol $\left( {{{\text{C}}_{\text{2}}}{{\text{H}}_{\text{5}}}{\text{OH}}} \right)$, acetaldehyde $\left( {{\text{C}}{{\text{H}}_{\text{3}}}{\text{CHO}}} \right)$ and secondary alcohols (${\text{C}}{{\text{H}}_{\text{3}}}{\text{CHROH}}$where R represents an alkyl or aryl group) in place of a methyl ketone. Iodoform is synthesized by treating any of these four compounds with iodine $\left( {{{\text{I}}_{\text{2}}}} \right)$ and sodium hydroxide $\left( {{\text{NaOH}}} \right)$ in the haloform reaction.
(2)Iodoform is often used as a disinfectant, mainly in hospitals. It was also earlier used in medicine for treating wounds as a healing and antiseptic dressing.
(3)A chemical test called iodoform test is used to check the presence of a methyl ketone moiety in an unknown substance. The presence of methyl ketone moiety means the presence of carbonyl compounds having the structure ${\text{C}}{{\text{H}}_{\text{3}}}{\text{COR}}$ or alcohols having the structure ${\text{C}}{{\text{H}}_{\text{3}}}{\text{CHROH}}$ where R is an alkyl or aryl group. The pale yellow precipitate of iodoform produced in this test confirms the presence of methyl ketone. The only aldehyde which gives a positive iodoform test is acetaldehyde since it contains a ${\text{C}}{{\text{H}}_{\text{3}}}{\text{CO - }}$ group.

Note:
Acetone is a methyl ketone since it has the structure ${\text{C}}{{\text{H}}_{\text{3}}}{\text{COR}}$ where R is a methyl group.