On combustion of 5.3 g of organic compound, 8.96 L of CO2 and 4.5 g of H2O were formed. When this substance is oxidized with a solution of potassium permanganate in sulfuric acid, a dibasic acid is formed, the carboxyl groups in which are in adjacent positions, and CO2 is not formed. Determine the molecular and structural formula of the substance.
General formula of the substance CxHy.
Let’s write the reaction equation:
CxHy + (x + y / 4) О2 = хСО2 + (y / 2) Н2О
Let’s determine the amount of substance carbon and hydrogen:
n (C) = n (CO2) = 8.96 / 22.4 = 0.4 mol
n (H) = n (H2O) * 2 = (4.5 / 18) * 2 = 0.5 mol
Thus, the ratio of the amounts of carbon and hydrogen in the original organic matter is approximately 4: 5.
Possible options include C4H5, C8H10, C12H15, C16H20.
Based on the general formulas of various classes of organic compounds, we find that the desired substance C8H10 (CnH2n-6) is 1,2-dimethylbenzene, since only it, in reaction with potassium permanganate in an acidic medium, forms a dibasic carboxylic acid, in which carboxyl groups are located in neighboring provisions
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