Halogenoalkanes and nucleophilic substitution · 卤代烷和亲核取代
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| halogenoalkane/ˈheɪləʊdʒnəʊlkeɪn/ | 卤代烷 | lǔ dài wán |
| nucleophilic substitution/ˌnjuːklɪəˈfɪlɪk ˌsʌbstɪˈtjuːʃn/ | 亲核取代 | qīn hé qǔ dài |
| nitrile/ˈnaɪtraɪl/ | 腈 | jīng |
| amine/ˈæmaɪn/ | 胺 | àn |
| reflux/ˈriːflʌks/ | 回流 | huí liú |
Swapping out a halogen
- A halogenoalkane 卤代烷 is an alkane with a halogen in place of hydrogen (a C–X bond).
- The C–X bond is polar, which makes these compounds react.
- They come in three classes.
换掉一个卤素
- 一个卤代烷(halogenoalkane)是一个用卤素代替氢的烷烃(一个 C–X 键)。
- C–X 键是极性的,这使这些化合物反应。
- 它们有三类。
A halogenoalkane is: · 一个卤代烷是:
A halogenoalkane has a polar C–X bond, which is the reactive site. · 一个卤代烷有一个极性的 C–X 键,它是活泼的位点。
Halogenoalkanes react with aqueous hydroxide ions by: · 卤代烷通过以下哪种与水性氢氧根离子反应:
OH⁻ is a nucleophile replacing the halogen. · OH⁻ 是一个替换卤素的亲核试剂。
Three classes
- primary, secondary or tertiary, set by how many carbons are joined to the carbon holding the halogen (one, two or three).
- Made by: free-radical substitution of an alkane, electrophilic addition to an alkene, or substitution of an alcohol.
The solvent decides whether a halogenoalkane substitutes or eliminates
Primary, secondary and tertiary halogenoalkanes
三类
- 伯(primary)、仲(secondary)或叔(tertiary),由多少个碳连接到持有卤素的碳决定(一个、两个或三个)。
- 由以下制造:一个烷烃的自由基取代、对一个烯烃的亲电加成,或一个醇的取代。
溶剂决定一个卤代烷是取代还是消除
伯、仲和叔卤代烷
Nucleophilic substitution · 亲核取代
A nucleophile swaps in for the leaving group on a halogenoalkane. · 一个亲核试剂换入,代替一个卤代烷上的离去基团。
A tertiary halogenoalkane has the halogen on a carbon joined to: · 一个叔卤代烷的卤素在一个连接到以下哪种的碳上:
Primary = 1 carbon attached, secondary = 2, tertiary = 3, on the carbon bearing the halogen. · 在带卤素的碳上,伯 = 连接 1 个碳,仲 = 2,叔 = 3。
Match each halogenoalkane idea. · 匹配每个卤代烷概念。
Each item links the term to its correct meaning. · 每一项把术语链接到它正确的含义。
In nucleophilic substitution, OH⁻ attacks the δ+ carbon and the halogen leaves as a halide ion. · 在亲核取代中,OH⁻ 进攻 δ+ 碳,卤素作为一个卤离子离开。
The C–X bond is polar, so the carbon is δ+ — exactly where an electron-pair donor attacks. · C–X 键是极性的,所以碳是 δ+——正是一个电子对供体进攻的地方。
Nucleophilic substitution 亲核取代
- The C–X carbon is slightly positive, so a nucleophile (lone-pair species) attacks and replaces the halogen.
| Reagent | Product |
|---|---|
| $\text{NaOH(aq)}$, heat | an alcohol |
| $\text{KCN}$ in ethanol, heat | a nitrile 腈 (adds a carbon) |
| $\text{NH}_3$ in ethanol, heat + pressure | an amine 胺 |
Many halogenoalkane reactions are carried out by heating under reflux 回流.
亲核取代
- C–X 碳稍微正,所以一个亲核试剂(nucleophile,孤对电子物种)进攻并替换卤素。
| 试剂 | 产物 |
|---|---|
| $\text{NaOH(aq)}$,加热 | 一个醇 |
| $\text{KCN}$ 在乙醇中,加热 | 一个腈(nitrile,加一个碳) |
| $\text{NH}_3$ 在乙醇中,加热 + 加压 | 一个胺(amine) |
许多卤代烷反应通过回流加热进行。
Warming a halogenoalkane with aqueous NaOH produces: · 把一个卤代烷与水性 NaOH 一起加热产生:
NaOH(aq) substitutes the halogen for –OH, giving an alcohol. · NaOH(aq) 把卤素取代为 –OH,给出一个醇。
Reaction with KCN in ethanol gives a nitrile, which is useful because it: · 与乙醇中的 KCN 反应给出一个腈,它有用因为它:
The CN group adds a carbon, lengthening the chain; NH₃ instead gives an amine. · CN 基团加一个碳,延长链;NH₃ 改为给出一个胺。
Identifying the halogen
- Warm with silver nitrate in ethanol: a silver halide precipitate forms — white AgCl, cream AgBr, yellow AgI.
Volatile halogenoalkanes were once widely used as refrigerants and aerosol propellants.
识别卤素
- 与乙醇中的硝酸银一起加热:一个银卤化物沉淀形成——白色 AgCl,奶油色 AgBr,黄色 AgI。
挥发性卤代烷曾经被广泛用作制冷剂和气溶胶推进剂。
You've got it
- a halogenoalkane has a polar C–X bond; classes are primary/secondary/tertiary
- nucleophilic substitution: NaOH(aq) → alcohol; KCN → nitrile (+1 carbon); NH₃ → amine
- identify the halogen with silver nitrate (white/cream/yellow precipitate)
你掌握了
- 一个卤代烷有一个极性的 C–X 键;类别是伯/仲/叔
- 亲核取代:NaOH(aq) → 醇;KCN → 腈(+1 碳);NH₃ → 胺
- 用硝酸银识别卤素(白色/奶油色/黄色沉淀)