Question

Which of the following compounds is responsible for iodoform reaction
(A) Formalin
(B) Methanol
(C) Acetic acid
(D) Ethanol

Answer 1

Hint: In the given question we need to identify which of the four given compounds is responsible for iodoform reaction. Iodoform test is used to check the presence of carbonyl compounds with the structure $R - CH(OH) - C{H_3}$ or alcohols with the structure $R - CH(OH) - C{H_3}$in a given unknown substance.

Complete Step by Step Answer:
The compounds with alpha methyl groups are the ones which give positive iodoform tests. If we talk more accurately, we are talking about ethanal and methyl ketones. The only aldehyde that gives us a positive iodoform test is called Ethanal. Also, ethanol is responsible for the iodoform test.

Suppose there is a compound which contains a methyl ketone or a secondary alcohol having a methyl group at alpha position. If we add iodine and sodium hydroxide to such compounds we will observe a pale yellow precipitate of iodoform is formed. This precipitate is also known as triiodomethane. This can be used to point out aldehydes or ketones. If there is an aldehyde which is giving a positive result for the iodoform test, then it must be acetaldehyde.

Some of the compounds that give positive results for iodoform test include acetaldehyde, ethanol, secondary alcohols containing methyl groups in alpha position and methyl ketones.

Ethanol is an organic compound that has the chemical formula ${C_2}{H_5}OH$. It is a volatile, flammable liquid with a pungent taste. It has no color. Its molar mass is $46.07\,g/mol$.
Hence, the correct option is D.

Note: The compounds which give positive iodoform tests are the ones with Alpha methyl groups. To be more precise, Ethanal (Acetaldehyde) and methyl ketones. Ethanal is the only aldehyde which gives positive iodoform test.