完全氧化
苯甲醇 → 苯甲酸：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
- 过量 KMnO4／OH-；随后进行酸性后处理
- 条件
- 与水溶液氧化剂一起加热，随后酸化
- 反应类别
- 完全氧化
- 方程式
- C6H5CH2OH + 2[O] -> C6H5COOH + H2O
概览
氧化先将苄位 CH2OH 转化为醛，再在碱性条件下转化为羧酸根。酸性后处理得到苯甲酸；芳环保留，侧链碳被进一步氧化。
转化
- 方程式
- C6H5CH2OH + 2[O] -> C6H5COOH + H2O
- 试剂
- 过量 KMnO4／OH-；随后进行酸性后处理
- 反应环境
- 与水溶液氧化剂一起加热，随后酸化
- 反应类别
- 完全氧化
- 机理
- 醇氧化
- Evidence level
- source-backed molecular example
参考步骤
Benzoic-acid purification and benzyl-alcohol separation
Crude benzoic acid containing residual benzyl alcohol → recrystallised benzoic acid
物料与用量
- Crude benzoic-acid sample
- Water as recrystallisation solvent
- Benzoic-acid and benzyl-alcohol reference samples
- Reference TLC solvents
仪器装置
- Recrystallisation and hot-filtration apparatus
- Suction-filtration apparatus
- TLC plate and development chamber
实验步骤
- Dissolve the crude solid in a suitable minimum amount of hot solvent and remove insoluble contamination.
- Allow crystallisation, then collect and dry the solid.
后处理与分离
- Compare crude material, recovered crystals and reference samples on the same TLC plate.
- Use the reference’s complementary visualisation methods when spots are poorly separated or visible.
关键控制条件
- The source uses a model impure benzoic-acid sample; oxidation reagents and their work-up remain route-specific.
- A single apparent TLC spot may hide overlapping compounds.
- Lower recovered mass can reflect removal of impurities as well as loss of product.
实验技术
重结晶
Purify a solid using its greater solubility in hot solvent than in cold solvent.
装置设置
- Choose a compatible solvent and dissolve the crude solid in the minimum practical amount of hot solvent.
- Remove insoluble matter while hot if required; cool the clear solution before collecting the crystals.
操作检查
- Excess solvent reduces recovery; some product remains in the mother liquor.
- Wash with a small amount of cold solvent and dry before weighing. Wet crystals give misleading yields.
Filtration under reduced pressure
Collect an insoluble solid while drawing the liquid through a filter using reduced pressure.
装置设置
- Clamp the flask and seat the paper with the specified solvent before collecting a cooled crystal suspension.
- Retain the filtrate until the desired solid has been recovered.
操作检查
- Use vacuum-rated glassware and the laboratory-approved vacuum setup.
- Release the vacuum safely before shutting down the suction source. Filtration removes bulk liquid; further drying may be needed.
薄层色谱
Compare starting material, product and reference samples using migration on the same stationary phase.
装置设置
- Draw a pencil baseline above the solvent and apply small, separate sample spots.
- Develop the plate, mark the solvent front promptly and visualise using the approved method.
- Calculate Rf as spot distance divided by solvent-front distance from the same baseline.
操作检查
- Compare samples on the same TLC plate using the same solvent.
- Protect eyes and skin during UV visualisation; avoid inhaling eluent vapour.
底物范围
- 适用范围
- Primary benzylic alcohol; oxidation occurs on the side chain.
- 来源说明
- Benzoate forms in alkaline solution; acid work-up gives benzoic acid. An aldehyde is an intermediate, not the endpoint under these conditions.
相关反应
- Side chain oxidation: Toluene → Benzoic acid
甲苯通过侧链氧化生成苯甲酸。
- Carbonyl reduction: Benzaldehyde → Benzyl alcohol
氢负离子进攻醛基碳，C=O 的 π 电子移向氧。醇盐质子化后得到苯甲醇；此过程不形成新的碳碳键，也不还原芳环。
- Aldehyde oxidation: Benzaldehyde → Benzoic acid
水与醛可逆加成，形成可继续氧化的水合物。醛基碳成为羧基碳；酸性后处理使先形成的苯甲酸根转化为苯甲酸。
- Acyl chloride preparation: Benzoic acid → Benzoyl chloride
与五氯化磷反应，以氯替代羧基中的 OH，保留酰基碳和芳环。新生成的酰氯更易发生亲核取代；其余原子进入 POCl3 和 HCl。
- Esterification: Benzoic acid → Ethyl benzoate
酸活化使乙醇可加成到苯甲酸上；经质子转移和脱水，形成苯甲酸乙酯。整个酰基取代过程中，芳环保持完整。
参考文献
- Organic Chemistry: Oxidation of AlcoholsJohn McMurry · OpenStax Organic Chemistry · 2023
Supports functional-group chemistry used to curate the linked examples. Checked 2026-09-16; named examples are applications of textbook scope, without claimed experimental yields.
- Benzoic-acid purification and TLC: Coursework conundrumRoyal Society of Chemistry · RSC Education
Purification and analysis of benzoic acid contaminated with benzyl alcohol and a model inorganic impurity.
- Purifying by recrystallisationRoyal Society of Chemistry · RSC Education
Solvent selection, soluble and insoluble impurities, recovery losses and residual-solvent error.
- Evaporation, filtration and crystallisation: teaching practical scienceRoyal Society of Chemistry · RSC Education
Distinguishes filtration, crystallisation and post-16 reduced-pressure isolation.
- Using thin-layer chromatography to investigate the reaction: teacher notesRoyal Society of Chemistry · RSC Education
Compares crude and recrystallised aspirin with a reference sample; extra spots suggest impurities.