【Daily Question】Theoretical Foundation 2020.09.20
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Multiple-choice question: Among the following substances, which one cannot cause the acidic potassium permanganate solution to lose its color? A. Benzaldehyde B. Ethylbenzene C. Benzene D. Styrene Answer: C Hint: An additional reward will be given to those who can explain the reasoning behind the answer; the answer can be found in the response
C Answer: Benzene derivatives that contain carbon-carbon double bonds, those in which the carbon atoms connecting the benzene rings have hydrogen atoms, as well as substances with strong reducing properties, can be oxidized by potassium permanganate. A. Ethylene contains an unsaturated bond, so it is easily oxidized by acidic potassium permanganate; therefore, A is incorrect； B. Acetylene contains unsaturated bonds, so it is easily oxidized by acidic potassium permanganate; therefore, B is incorrect ； C. Benzene is relatively stable and not easily oxidized by acidic potassium permanganate, hence C is correct ； D. The methyl group in toluene contains hydrogen atoms, so it is easily oxidized by potassium permanganate; therefore, D is incorrect ； Therefore, the answer is C
Answer C: Benzene derivatives that contain carbon-carbon double bonds, those in which the carbon atoms connecting the benzene rings have hydrogen atoms, as well as substances with strong reducing properties, can be oxidized by potassium permanganate. A. Ethylene contains an unsaturated bond, so it is easily oxidized by acidic potassium permanganate; therefore, A is incorrect； B. Acetylene contains unsaturated bonds, so it is easily oxidized by acidic potassium permanganate; therefore, B is incorrect ； C. Benzene is relatively stable and not easily oxidized by acidic potassium permanganate, hence C is correct ； D. The methyl group in toluene contains hydrogen atoms, so it is easily oxidized by potassium permanganate; therefore, D is incorrect ； Therefore, the answer is C
The answer is C, benzene. Since benzene does not react with acidic potassium permanganate, it cannot be used to decolorize acidic potassium permanganate solutions.