碳骨架构建路线与提纯产物
引入| English | 释义 | 拼音 |
|---|---|---|
| Grignard reagent | 格氏试剂 | gé shì shì jì |
| work-up | 后处理 | hòu chǔ lǐ |
| Recrystallisation | 重结晶 | zhòng jié jīng |
| purity | 纯度 | chún dù |
Decide which carbon fragment to add
- A Grignard reagent 格氏试剂 forms from a halogenoalkane and Mg in dry ether. Water consumes it before carbonyl addition.
- Ethylmagnesium bromide plus ethanal bonds two carbon fragments into a four-carbon skeleton.
格氏试剂制备所用的醚类溶剂必须是_____。
难度 1/5 · 今日首次完成可获 100 金币及少量额外奖励
水会消耗该试剂，生成碳氢化合物。
Separate addition from work-up
- The carbonyl carbon gains the Grignard carbon group. Acidic work-up 后处理 changes the oxygen-containing intermediate into the alcohol.
- Ethanal with ethylmagnesium bromide gives butan-2-ol. Methanal instead gives propan-1-ol; CO₂ then acid gives propanoic acid.
溴乙基镁与甲醛反应后酸化，生成哪种醇？
难度 1/5 · 今日首次完成可获 100 金币及少量额外奖励
甲醛提供一个碳原子连接到含两个碳的乙基上。
Use every analytical observation
- C₃H₆O with C=O, an aldehyde proton and positive Tollens’ test supports propanal. Propanone fails the aldehyde observations.
- Predict NMR environments and compare with all supplied data. One matching observation alone rarely identifies a unique structure.
2.76 g salicylic acid at M 138 is 0.0200 mol, giving theoretical aspirin 3.60 g at M 180. A dry 2.52 g is 70.0% yield.
Choose isolation for the product
- Reflux retains volatile reactants; distillation collects a volatile product. Extraction separates immiscible liquid layers.
- Carbonate washing removes acidic impurities and releases CO₂. Vent the separating funnel; organic solvent is not always the upper layer.
有机层始终位于水层上方。
难度 1/5 · 今日首次完成可获 100 金币及少量额外奖励
层的位置取决于相对密度；密度较大的有机溶剂可能位于水层下方。
Measure yield only after drying
- Recrystallisation 重结晶 uses minimum hot solvent, cooling, filtration and a little cold-solvent wash. Dry the product before weighing.
- Aspirin yield uses limiting salicylic acid in a 1:1 mole ratio. A narrow melting range supports purity 纯度 but does not prove identity alone.
Water added before Grignard addition destroys the reagent rather than improving its alcohol yield.
Track carbon count and functional-group changes through every synthesis step. Choose dry conditions where needed, then separate, purify and dry before calculating yield.
理论阿司匹林产量为 3.60 g，实际干燥产物为 2.52 g。求产率百分比。
难度 2/5 · 今日首次完成可获 140 金币及少量额外奖励
2.52/3.60 × 100 = 70.0%.
哪两项操作能提升对真实固体产物产率/纯度的评估？
难度 2/5 · 今日首次完成可获 140 金币及少量额外奖励
干重可避免水分干扰；熔点范围可提供额外的纯度证据。