【Daily Question】Theoretical Foundation 2020.09.18
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Multiple-choice question: Insects can secrete pheromones. The following is a structural formula of a pheromone: CH3(CH2)5CH=CH(CH2)9CHO. Which of the following statements is correct? A. This pheromone cannot undergo an addition reaction with bromine; B. It can undergo a silver mirror reaction; C. It can react with only 1 mol of H2; D. It is a homolog of ethylene. Answer: B Hint: An additional reward will be given to those who can explain the solution process; the answer can be seen in the response
B. It can undergo a silver mirror reaction;
B. It can undergo a silver mirror reaction;
The last edit to this post was made by h20090630 on 2020-9-18 at 13:43; in step B ①, bromine water is added, and the phenomenon observed is that the color of the bromine water fades； ②Add an acidic solution of potassium permanganate, and the purple color of the acidic potassium permanganate solution fades. However, since aldehyde groups can also cause the purple color of acidic potassium permanganate solution to fade, only method ① can be chosen. Common methods for identifying aldehyde groups include: ① Adding silver ammonia solution, which utilizes the silver mirror reaction ； ②Add freshly prepared Cu(OH)2 and heat it to observe whether a red precipitate forms. Both of these methods can be used to identify aldehyde groups in this problem. Functional groups, identification methods and experimental phenomena, chemical equations for related reactions, reaction categories: http://img.zuoyebang.cc/zyb_1c0fe44a13a685a66771530629d2199c.jpg (Carbon-carbon double bond): When bromine water is added, the color of the bromine water fades. CH3(CH2)5CH====CH(CH2)9CHO + Br2 → CH3(CH2)5CHBr-BrCH(CH2)9CHO; this is an addition reaction. –CHO (aldehyde group): When treated with silver ammonia solution, a silver mirror is formed. CH3(CH2)5CH==CH(CH2)9CHO + 2[Ag(NH3)2]+ + 2OH- → CH3(CH2)5CH==CH(CH2)9COO- + http://img.zuoyebang.cc/zyb_1a593cfdd536c7f6eb789c0c333feaab.jpg + 2Ag↓ + 3NH3 + H2O; this is an oxidation reaction