A toxic compound “A” when reacted with NaCN in aqueous acidic medium yields an edible cooking component and food preservative “B”. “B” is converted to “C” by dibromane and can be used as an additive to petrol to reduce emission. “C” upon reaction with oleum at 140°C yields an inhalable anesthetic “D”. Identify “A”, “B”, “C”, and “D”, respectively.