氯化
Alcohols → Chloroalkanes · 氯化：查看反应物、产物、反应条件与来源依据，探索相关转化和合成路径。
- 试剂
- PCl5
- 条件
- 室温
- 反应类别
- 卤化
- 方程式
- R-OH + PCl5 -> R-Cl + POCl3 + HCl
概览
醇可转化为氯代烷，为后续取代反应引入更易离去的基团。
转化
- 方程式
- R-OH + PCl5 -> R-Cl + POCl3 + HCl
- 试剂
- PCl5
- 反应环境
- 室温
- 反应类别
- 卤化
- 机理
- 卤化
- Evidence level
- 教材核心内容
参考步骤
2-Chloro-2-methylpropane preparation
2-甲基-2-丙醇 → 2-氯-2-甲基丙烷
物料与用量
- 2-Methylpropan-2-ol and hydrochloric acid
- Hydrogencarbonate wash and suitable drying agent; quantities from the cited method
仪器装置
- 分液漏斗
- Dry flask
- Distillation apparatus
实验步骤
- Follow the cited mixing stage; formation of a second layer provides a visible separation, not proof of purity.
- Separate the organic layer, wash as directed and release pressure during the gas-forming hydrogencarbonate wash.
后处理与分离
- Dry, remove the drying agent and collect the stated distillation fraction.
- Compare the boiling range and supporting identity evidence with the intended product.
关键控制条件
- Hydrogen chloride fumes require appropriate extraction; the organic liquids are flammable.
- This tertiary-alcohol example must not be treated as evidence that every primary alcohol reacts under identical conditions.
实验技术
Liquid–liquid work-up
Separate the organic product layer from the aqueous reaction mixture, then wash and dry it before final purification.
装置设置
- Identify which layer contains the product from density data or a small drop test; do not assume the organic layer is always on top.
- Invert gently during washing and vent frequently away from people, especially when carbonate wash produces carbon dioxide.
- Drain and retain both layers until product identity has been confirmed.
- Dry the isolated organic layer until the drying agent remains free-flowing, then decant or filter before final distillation.
操作检查
- Remove the stopper before draining through the tap.
- Release pressure after each inversion during gas-forming washes.
- Record which layer was retained at every wash.
Drying an organic liquid
Remove residual water from a separated organic layer with a compatible anhydrous drying agent.
装置设置
- Remove visible aqueous liquid before treating the organic phase.
- Mix with small portions of drying agent, allow contact and separate the clear liquid from the solid before final purification.
操作检查
- Choose the agent for the product: a drying agent must not react with or strongly retain it.
- Drying removes water, not dissolved organic impurities; boiling-range or spectroscopic checks are still needed.
Distillation setup
Rearrange the apparatus to collect a volatile product or fraction instead of returning condensate to the reaction flask.
装置设置
- Position the thermometer bulb at the entrance to the condenser so it measures vapour entering the condenser.
- Run cooling water into the lower condenser connection and out through the upper connection.
- Heat gradually and collect only the fraction specified by the cited boiling range or procedure.
操作检查
- Do not distil a flask to dryness.
- Use an electric heat source for flammable mixtures.
- Change from reflux to distillation only after heating has stopped and the apparatus has cooled enough to handle safely.
底物范围
- 适用范围
- Alcohols react with phosphorus(V) chloride to form chloroalkanes.
- 来源说明
- The route records the PCl5 transformation; the mechanism diagram uses a primary-alcohol exemplar and is not generalized to secondary/tertiary alcohols or SOCl2 conditions.
相关反应
- Chlorination with thionyl chloride: Alcohols → Chloroalkanes
氯化亚砜将醇转化为氯代烷，同时生成二氧化硫和氯化氢。
- Bromination: Alcohols → Bromoalkanes
在溴化物和酸的作用下，醇转化为溴代烷。
- Iodination: Alcohols → Iodoalkanes
在碘和红磷的作用下，醇转化为碘代烷。
- Hydrochlorination: Alkenes → Chloroalkanes
氯化氢在烯烃双键两端加成，可生成氯代烷。
- Hydrolysis: Chloroalkanes → Alcohols
氢氧根可取代 C-Cl 中的氯，形成醇。
- Cyanation: Chloroalkanes → Nitriles
氰根取代生成腈，使碳链增加一个碳原子。
- Amination: Chloroalkanes → Amines
氨取代氯，形成伯胺；过量氨可限制进一步烷基化。
- Elimination: Chloroalkanes → Alkenes
碱促进的消去反应脱去 HCl，生成烯烃。
- Hydrolysis: Bromoalkanes → Alcohols
氢氧根可取代 C-Br 中的溴，形成醇。
- Hydrolysis: Iodoalkanes → Alcohols
氢氧根可取代 C-I 中的碘，形成醇。
- Oxidation: Alcohols → Aldehydes
伯醇经受控氧化可生成醛。
- Oxidation: Alcohols → Ketones
仲醇氧化生成酮。
- Oxidation: Alcohols → Carboxylic acids
伯醇充分氧化生成羧酸。
- Free radical chlorination: Alkanes → Chloroalkanes
光化学氯化可将烷烃转化为氯代烷。
- Hydration: Alkenes → Alcohols
催化水合将烯烃转化为醇。
- Dehydration: Alcohols → Alkenes
脱水将醇转化为烯烃。
参考文献
- Pearson Edexcel Level 3 Advanced GCE in Chemistry specificationPearson Education Limited · Pearson qualifications · 2024
Supports the textbook-core organic reaction routes used for displayed route and mechanism content.
- Core practical 6: Investigating chlorination of 2-methylpropan-2-olPearson Education Limited · Pearson qualifications
Tertiary chloroalkane preparation, washing, drying and distillation.
- Pearson Edexcel International Advanced Level Chemistry Student Practical GuidePearson Education Limited · Pearson qualifications · 2018
Supports the practical distinctions between reflux, distillation, liquid-liquid separation, washing and drying in organic preparations.
- Reflux and distillation – practical videosRoyal Society of Chemistry · RSC Education
Explains the different purposes and apparatus arrangements for reflux and distillation, including organic preparation and work-up.