Alkenes and their reactions · 烯烃和它们的反应
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| alkene/ˈælkiːn/ | 烯烃 | xī tīng |
| electrophilic addition/ɪˌlektrəʊˈfɪlɪk əˈdɪʃn/ | 亲电加成 | qīn diàn jiā chéng |
| elimination/ɪˌlɪmɪˈneɪʃn/ | 消去 | xiāo qù |
| dehydration/ˌdiːhaɪˈdreɪʃn/ | 脱水 | tuō shuǐ |
| bromine water/ˈbrəʊmaɪn ˈwɔːtə/ | 溴水 | xiù shuǐ |
The reactive double bond
- Alkenes 烯烃 have a C=C double bond ($\text{C}_n\text{H}_{2n}$).
- That double bond is the functional group, so alkenes are reactive.
- Most reactions are electrophilic addition 亲电加成.
活泼的双键
- 烯烃(alkenes)有一个 C=C 双键($\text{C}_n\text{H}_{2n}$)。
- 那个双键是官能团,所以烯烃是活泼的。
- 大多数反应是亲电加成(electrophilic addition)。
Alkene addition route · 烯烃加成途径
Follow how the C=C bond opens and new atoms add. · 跟踪 C=C 键如何打开和新原子如何加上。
Alkenes are reactive because they have: · 烯烃活泼,因为它们有:
The electron-rich C=C double bond is the reactive functional group of alkenes (CₙH₂ₙ). · 电子富的 C=C 双键是烯烃(CₙH₂ₙ)的活泼官能团。
Adding bromine water to an alkene turns it from orange to: · 给一个烯烃加溴水使它从橙色变成:
The bromine adds across the double bond. · 溴跨双键加上。
Making alkenes
- elimination 消去 of HX from a halogenoalkane (NaOH in ethanol, heat).
- dehydration 脱水 of an alcohol (hot $\text{Al}_2\text{O}_3$ or conc. sulfuric acid).
- cracking of a longer alkane.
Cracking heavy fractions in a refinery produces alkenes
制造烯烃
- 从一个卤代烷消除(elimination)HX(NaOH 在乙醇中,加热)。
- 一个醇的脱水(dehydration,热 $\text{Al}_2\text{O}_3$ 或浓硫酸)。
- 一个更长的烷烃的裂解。
在炼油厂裂解重馏分产生烯烃
Which makes an alkene? · 哪个制造一个烯烃?
Removing water from an alcohol (dehydration), or HX from a halogenoalkane (elimination), makes an alkene. · 从一个醇移除水(脱水),或从一个卤代烷移除 HX(消除),制造一个烯烃。
Match each alkene fact. · 匹配每个烯烃事实。
Each item links the term to its correct meaning. · 每一项把术语链接到它正确的含义。
An alkene decolourises bromine water, while an alkane leaves it orange — that is the standard test for a C=C double bond. · 一个烯烃使溴水褪色,而一个烷烃使它保持橙色——那是 C=C 双键的标准检验。
The π electrons of the C=C attack the bromine; alkanes have no double bond, so nothing happens. · C=C 的 π 电子进攻溴;烷烃没有双键,所以什么都不发生。
Addition reactions
| Reagent | Product |
|---|---|
| $\text{H}_2$ (Pt/Ni, heat) | alkane |
| steam + $\text{H}_3\text{PO}_4$ | alcohol |
| $\text{HX}$ | halogenoalkane |
| $\text{X}_2$ | di-substituted alkane |
- Cold dilute $\text{KMnO}_4$ gives a diol; hot concentrated $\text{KMnO}_4$ breaks the C=C apart.
加成反应
| 试剂 | 产物 |
|---|---|
| $\text{H}_2$(Pt/Ni,加热) | 烷烃 |
| 蒸汽 + $\text{H}_3\text{PO}_4$ | 醇 |
| $\text{HX}$ | 卤代烷 |
| $\text{X}_2$ | 二取代烷烃 |
- 冷稀 $\text{KMnO}_4$ 给出一个二醇;热浓 $\text{KMnO}_4$ 把 C=C 分开。
Adding steam (with an H₃PO₄ catalyst) to an alkene gives: · 给一个烯烃加蒸汽(用一个 H₃PO₄ 催化剂)给出:
Electrophilic addition of water (steam) across the C=C makes an alcohol. · 水(蒸汽)跨 C=C 的亲电加成制造一个醇。
Test for C=C
- Shake with orange bromine water 溴水: an alkene decolourises it (electrophilic addition); an alkane does not.
C=C 的检验
- 与橙色溴水(bromine water)摇晃:一个烯烃使它褪色(亲电加成);一个烷烃不会。
When an alkene is shaken with orange bromine water, the bromine water: · 当一个烯烃与橙色溴水摇晃时,溴水:
Alkenes decolourise bromine water by electrophilic addition; alkanes leave it orange. · 烯烃通过亲电加成使溴水褪色;烷烃使它保持橙色。
You've got it
- alkenes = C=C double bond ($\text{C}_n\text{H}_{2n}$), reactive; made by elimination, dehydration or cracking
- most reactions are electrophilic addition (H₂ → alkane, steam → alcohol, HX → halogenoalkane)
- bromine water test: an alkene decolourises it
你掌握了
- 烯烃 = C=C 双键($\text{C}_n\text{H}_{2n}$),活泼;由消除、脱水或裂解制造
- 大多数反应是亲电加成(H₂ → 烷烃,蒸汽 → 醇,HX → 卤代烷)
- 溴水检验:一个烯烃使它褪色