Baeyer's reagent is :
- Acidic potassium permanganate solution
- Acidic potassium dichromate solution
- Cold, dilute, aqueous solution of potassium permanganate
- Hot, concentrated solution of potassium permanganate
Answer
(3) Cold, dilute, aqueous solution of potassium permanganate
Solution
Baeyer's reagent is a cold, dilute, aqueous (slightly alkaline) solution of KMnO4.
It is used to test unsaturation: the purple colour disappears as alkenes are converted into vicinal glycols, e.g.
CH2=CH2 + H2O + [O] dil. KMnO4 HOCH2-CH2OH
Answer: (3)