碘仿反应
乙醇 → 三碘甲烷 个产物：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
- I2(aq), NaOH(aq)
- 条件
- 温和加热
- 反应类别
- 碘仿反应
- 方程式
- CH3CH2OH + 4 I2 + 6 OH- -> HCO2- + CHI3 + 5 I- + 5 H2O
概览
乙醇被碱性碘溶液氧化并断裂，生成三碘甲烷和甲酸盐。
转化
- 方程式
- CH3CH2OH + 4 I2 + 6 OH- -> HCO2- + CHI3 + 5 I- + 5 H2O
- 试剂
- I2(aq), NaOH(aq)
- 反应环境
- 温和加热
- 反应类别
- 碘仿反应
- 机理
- oxidation followed by haloform reaction
- Evidence level
- 教材核心内容
参考步骤
Microscale iodoform test
Ethanol gives a yellow triiodomethane precipitate
物料与用量
- Ethanol sample
- Iodine solution and sodium hydroxide; use the cited microscale quantities
- Approved negative comparison sample
仪器装置
- Small labelled test tubes
- Dropping pipettes
实验步骤
- Treat the sample and comparison using the same reagent sequence and observation period from the source.
- Record cloudiness and yellow precipitate formation separately from disappearance of iodine colour.
后处理与分离
- Keep the test mixture for the laboratory’s disposal procedure; do not isolate the diagnostic solid.
关键控制条件
- A positive result supports the required methyl-carbonyl structure or an oxidisable precursor. It does not uniquely identify ethanol.
- Ethanol is the primary-alcohol exception; suitable methyl secondary alcohols and methyl ketones also respond.
- Use eye protection and handle iodine and alkali as specified by the source.
实验技术
Controlled comparison of reaction times
Compare a visible change while keeping variables other than the one under study consistent.
装置设置
- Use equal concentrations, volumes and mixing methods, and equilibrate samples at the same temperature.
- Define the visible endpoint before starting and record repeated measurements.
操作检查
- Precipitation time includes mixing and detection thresholds; its inverse is only a relative-rate proxy under matched conditions.
- Do not compare different carbon skeletons when isolating the effect of halogen identity.
底物范围
- 适用范围
- 在这些条件下，乙醇先氧化为乙醛，再发生卤仿断裂，因此能发生碘仿反应。
- 来源说明
- 此路线的底物为乙醇。
相关反应
- Iodoform reaction: Methyl ketones → Triiodomethane 个产物
碱性碘溶液将甲基酮转化为黄色三碘甲烷和减少一个碳原子的羧酸盐。
- Iodoform reaction: Ethanal → Triiodomethane 个产物
乙醛在碱性碘溶液中发生碘仿反应，生成三碘甲烷和甲酸盐。
- Iodoform reaction: Methyl secondary alcohols → Triiodomethane 个产物
含 CH3CH(OH)- 结构的仲醇先氧化为甲基酮，再断裂生成三碘甲烷和减少一个碳原子的羧酸盐。
- Partial oxidation: Ethanol → Ethanal
乙醇氧化为乙醛。
- Oxidation: Ethanol → Ethanoic acid
乙醇氧化为乙酸。
- Reduction: Ethanal → Ethanol
乙醛还原为乙醇。
- Esterification: Ethanol → Ethyl acetate
乙酸与乙醇可逆反应，形成乙酸乙酯和水。
- Acid hydrolysis: Ethyl acetate → Ethanol
乙酸乙酯与水可逆反应，形成乙酸和乙醇。
- Hydration: Ethene → Ethanol
乙烯通过水合生成乙醇。
- Dehydration: Ethanol → Ethene
乙醇通过脱水生成乙烯。
- Intermolecular dehydration: Ethanol → Diethyl ether
质子化使一个乙醇分子的羟基成为更易离去的基团。另一个乙醇分子的氧取代水，随后去质子化生成乙醚；更强的脱水条件则有利于生成乙烯。
- Hydrolysis: Bromoethane → Ethanol
氢氧根进攻与溴相连的饱和碳，同时 C-Br 键断裂。该伯底物的 SN2 路线以 OH 取代溴，并保留两个碳原子；水溶液条件较有利于这一取代分支，而非消去。
- Acid hydrolysis: Ethyl butyrate → Ethanol
水进攻与质子转移，使乙氧基片段以乙醇形式离去。另一部分重新形成羰基，生成丁酸。
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.
- A test to distinguish between ethanol and methanolRoyal Society of Chemistry and Nuffield Foundation · RSC Education
Microscale iodoform observation and the functional-group scope of positive results.
- Rates of hydrolysis: practical videos for 16–18 studentsRoyal Society of Chemistry · RSC Education
Water is the nucleophile in the silver-nitrate comparison, and silver-halide precipitation measures released halide indirectly.