Question

Which of the following gives the haloform test.
A) \[{H_2}C - C\left( O \right) - C{H_3}\]
B) \[{H_2}C - C\left( OH \right) - C{H_3}\]
C) \[{H_2}C - C{H_2} - OH\]
i) A only
ii) A and B
iii) A,B,C
iv) none of these

Answer 1

Hint: Haloform reaction is also called the iodoform reaction with sodium salts is used for the detection of the ketone group which is produced on oxidation . Further we should know that only and only methyl ketones which are acetaldehyde and two degree alcohol give iodoform test.

Complete step-by-step answer:
We should know that the aldehydes and ketones having at least one methyl group linked to the carbonyl carbon atom are oxidised by sodium salts of corresponding carboxylic acid having one carbon atom less than that of the carbonyl group .
Haloform reaction is also called the iodoform reaction with sodium salts is used for the detection of the ketone group which is produced on oxidation.
When the halogen is used which is iodine. This haloform test can be used to identify methyl ketones because iodoform is a yellow solid with the characteristic odour
Further we should know that only and only methyl ketones which are acetaldehyde and two degree alcohol give iodoform test.
So accordingly we can discuss each one to know which of them show haloform test.
Now talking about the first one
It is a ketone so it will give the haloform test
Coming to the second one we can say that it is two degree alcohol, so it will also give a haloform test.
When we talk about the third one we will see that it is an alcohol but not two degrees so, it will not give a haloform test.
Hence the second option is correct.

Additional information:
We should know one interesting fact that when the iodine and the sodium hydroxide are used as the reagent a positive reaction will give iodoform which is further solid at room temperature. This also,further tends to precipitate out of the solution causing a distinctive cloudiness.

Note: This reaction can be used to convert a terminal methyl ketone into the analogous carboxylic acid. and only methyl ketones which are acetaldehyde and two degree alcohol give iodoform test. So accordingly we can discuss each one to know which of them show haloform test.