Structure of A, based on the following reaction, is

Concept:

Bayer's reagent, also known as alkaline potassium permanganate, is a solution used to test for the presence of unsaturation (double or triple bonds) in organic compounds.

Explanation:

• Alkaline KMnO₄ acts as Bayers reagent which involves the reduction of the permanganate ion (MnO₄^-) to manganese dioxide (MnO₂), while the alkene is oxidized to form the 1,2-diol.

• 1,2-diol undergoes rearrangement and then oxidised to carboxylic acid in the presence of alk.KMnO₄. Alk. KMnO₄ acts as strong oxidizing agent which involves conversion of alcohol, aldehydes and ketones to their corresponding carboxylic acids.

Conclusion:

Hence, the reactant involves in the reaction is 2,2-dimethyl-3-methylidenebicyclo-[2,2,1]heptane.