An unknown compound K is insoluble in water and soluble in cold, concentrated H₂SO₄. It gives a blue-green precipitate with the chromic acid reagent. When mixed with Lucas reagent, a separate layer is formed after 5 minutes. Bromine solution is immediately decolorized when added to the unknown. What is the molecular formula, IHD, structure, and name of the unknown if its molecular weight is 86 g/mol?