Question

What is the reaction of following on $but - 2 - ene$ ?
(A) Dil alkaline $KMn{O_4}$
(B) Acidic $KMn{O_4}$

Answer 1

$Potassium{\text{ }}permanganate$ is an oxidising agent. On reacting with alkene it gives different products depending upon what type of $Potassium{\text{ }}permanganate$ is present, whether cold, acidic or alkaline $Potassium{\text{ }}permanganate$ reacting with alkene.

Complete answer:
When $Potassium{\text{ }}permanganate$ , an oxidizing agent, is added to an alkene it results in ketogenic or acidic compound formation. An alkaline solution of cold $Potassium{\text{ }}permanganate$ is called Baeyer’s reagent, which is a potent oxidizing agent. Alkene on reaction with cold, dilute or aqueous solution of $Potassium{\text{ }}permanganate$ produces vicinal glycols.
When dilute alkaline $KMn{O_4}$ reacts with the $but - 2 - ene$ a diol product is formed, which is $butane - 2,3 - diol$ . First it breaks the carbon-carbon double bond and then the resultant product is converted into a diol. The reaction is –
$C{H_3} - CH = CH - C{H_3} + H - OH + [O] \to {(C{H_3}CHOH)_2}$
Alkene in reaction with acidic $KMn{O_4}$ are converted into carboxylic group formation. When $but - 2 - ene$ is treated with acidic $KMn{O_4}$ , the carbon-carbon double bond breaks down due to the action of this oxidising agent. This results in the formation of $acetic{\text{ }}acid$

Additional information:
The following point should be kept in mind when deriving the end product with a carbon-carbon double bond:
If there are two alkyl groups at one end of the bond, that part of the molecule will give ketone.
If there is one alkyl group and one hydrogen at one end of the bond, that part of the molecule will give carboxylic acid.
If there are two hydrogens at one end of the bond, that part will give carbon dioxide and water.

Note:
$Potassium{\text{ }}permanganate$ is a purple-black crystalline solid. Alkaline $Potassium{\text{ }}permanganate$ is used for the identification of a compound whether it contains saturated or unsaturated bonds. Thus it helps in testing the unsaturation of a compound. It is widely used in titration, treating bacterial or fungal infections or dressing wounds.