Arenes and their reactions · 芳烃及其反应
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| arene/ˈæren/ | 芳烃 | fāng tīng |
| electrophilic substitution/ɪˌlektrəʊˈfɪlɪk ˌsʌbstɪˈtjuːʃn/ | 亲电取代 | qīn diàn qǔ dài |
| halogenation/həˌlɒdʒəˈneɪʃn/ | 卤化 | lǔ huà |
| nitration/naɪˈtreɪʃn/ | 硝化 | xiāo huà |
| Friedel–Crafts/ˈfriːdl kræfts/ | 傅-克反应 | fù - kè fǎn yìng |
The chemistry of the ring
- Arenes 芳烃 are aromatic hydrocarbons, built on the benzene ring.
- The stable, electron-rich ring reacts mostly by electrophilic substitution 亲电取代.
- This keeps the ring, rather than destroying it by addition.
环的化学
- 芳烃(arenes)是芳香烃,建立在苯环上。
- 稳定的、电子富集的环主要通过亲电取代反应。
- 这保留环,而不是通过加成破坏它。
Arene substitution route · 芳烃取代途径
Follow electrophilic substitution on benzene. · 跟随苯上的亲电取代。
Benzene reacts mostly by electrophilic substitution because: · 苯主要通过亲电取代反应,因为:
Substitution preserves the aromatic stabilisation; addition would break up the delocalised system. · 取代保留芳香稳定;加成会破坏离域系统。
Arenes such as benzene typically react by: · 像苯这样的芳烃通常通过以下方式反应:
Substitution keeps the stable ring intact. · 取代保持稳定的环完好。
Reactions of benzene
| Reaction | Reagents | Product |
|---|---|---|
| halogenation 卤化 | $\text{Cl}_2$/$\text{Br}_2$ + $\text{AlCl}_3$ | a halogenoarene |
| nitration 硝化 | conc. $\text{HNO}_3$ + conc. $\text{H}_2\text{SO}_4$ | nitrobenzene |
| Friedel–Crafts 傅-克反应 | $\text{RCl}$ or $\text{RCOCl}$ + $\text{AlCl}_3$ | adds an alkyl/acyl group |
| side-chain oxidation | hot alkaline $\text{KMnO}_4$ | benzoic acid |
| hydrogenation | $\text{H}_2$, Pt/Ni | cyclohexane |
The main reactions of benzene
苯的反应
| 反应 | 试剂 | 产物 |
|---|---|---|
| 卤化 | $\text{Cl}_2$/$\text{Br}_2$ + $\text{AlCl}_3$ | 一个卤代芳烃 |
| 硝化 | 浓 $\text{HNO}_3$ + 浓 $\text{H}_2\text{SO}_4$ | 硝基苯 |
| 傅瑞德—克拉夫茨 | $\text{RCl}$ 或 $\text{RCOCl}$ + $\text{AlCl}_3$ | 加一个烷基/酰基 |
| 侧链氧化 | 热碱性 $\text{KMnO}_4$ | 苯甲酸 |
| 氢化 | $\text{H}_2$,Pt/Ni | 环己烷 |
苯的主要反应
Nitration of benzene uses: · 苯的硝化用:
The conc. acid mixture generates the NO₂⁺ electrophile, giving nitrobenzene. · 浓酸混合物生成 NO₂⁺ 亲电试剂,给出硝基苯。
A Friedel–Crafts reaction (with AlCl₃) is used to: · 一个傅瑞德—克拉夫茨反应(用 AlCl₃)用来:
Friedel–Crafts alkylation/acylation adds a carbon-based group to benzene. · 傅瑞德—克拉夫茨烷基化/酰基化给苯加一个碳基的基团。
Match each term to its meaning. · 匹配每个术语和它的含义。
Each item links the term to its correct meaning. · 每一项把术语链接到它正确的含义。
Benzene reacts mainly by electrophilic substitution, not addition, because that keeps its stable delocalised ring intact. · 苯主要通过亲电取代而不是加成反应,因为那保持它稳定的离域环完好。
Addition would break the delocalised ring and lose its stability, so substitution (swapping an H) is favoured. · 加成会破坏离域环并失去它的稳定性,所以取代(换掉一个 H)被偏好。
The mechanism (nitration)
- The acid mix makes the electrophile $\text{NO}_2^+$.
- the ring's delocalised electrons bond to the electrophile → an unstable intermediate.
- an $\text{H}^+$ is lost, restoring the stable ring.
- Substitution wins because it keeps the delocalisation; addition would destroy it.
Naphthalene, used in mothballs, is a simple arene of two fused benzene rings.
机理(硝化)
- 酸混合物生成亲电试剂 $\text{NO}_2^+$。
- 环的离域电子与亲电试剂键合 → 一个不稳定的中间体。
- 一个 $\text{H}^+$ 失去,恢复稳定的环。
- 取代胜出,因为它保留离域;加成会破坏它。
萘,用于卫生球,是一个两个稠合苯环的简单芳烃。
In electrophilic substitution, after the ring bonds to the electrophile: · 在亲电取代中,环与亲电试剂键合之后:
Losing H⁺ from that carbon restores the delocalised ring, completing the substitution. · 从那个碳失去 H⁺ 恢复离域环,完成取代。
Why substitution, not addition
- Benzene reacts by substitution to preserve its stable delocalised ring.
- Addition would destroy the extra stability, so it is not favoured.
Friedel-Crafts: alkylation adds an alkyl group, acylation an acyl group
为什么取代,不是加成
- 苯通过取代反应以保留它稳定的离域环。
- 加成会破坏额外的稳定性,所以它不被偏好。
You've got it
- arenes react by electrophilic substitution (keeping the ring)
- key reactions: halogenation, nitration, Friedel–Crafts (add alkyl/acyl), side-chain oxidation (→ benzoic acid), hydrogenation
- mechanism: ring attacks the electrophile → intermediate → loses H⁺ to restore the ring
你掌握了
- 芳烃通过亲电取代反应(保留环)
- 关键反应:卤化、硝化、傅瑞德—克拉夫茨(加烷基/酰基)、侧链氧化(→ 苯甲酸)、氢化
- 机理:环攻击亲电试剂 → 中间体 → 失去 H⁺ 以恢复环