📚 Combined 190: Organic Synthesis & Analysis | 组合190：有机合成与分析
Combined 190 for Edexcel A-Level Chemistry is a focused revision resource that integrates multi-step organic synthesis with modern analytical techniques. It requires students to design synthetic pathways, predict products, deduce reaction mechanisms, and interpret spectra from IR, mass spectrometry, ¹³C NMR, and ¹H NMR. The module hones higher-order problem-solving skills that are regularly examined in Paper 2 and Paper 3.
Edexcel A-Level化学的组合190是一份针对性复习资料，将多步有机合成与现代分析技术有机结合。它要求学生设计合成路线、预测产物、推导反应机理，并解析红外光谱、质谱、碳-13核磁共振谱和氢核磁共振谱。该模块锤炼的高阶解题能力在Paper 2和Paper 3中频频出现。
1. Overview of Combined 190 | 组合190概述
Combined 190 is not a single textbook chapter but a synthesis of topics from the Edexcel specification, primarily focusing on organic chemistry (Topic 6, 17, 18) and analytical techniques (Topic 7, 19). It represents the type of synoptic question where students must link functional group chemistry with spectral evidence to propose a structure or a full synthetic route.
组合190并非单一的课本章节，而是Edexcel考纲中有机化学（主题6、17、18）与分析技术（主题7、19）的综合体。它代表的是一类综合性问题：学生需要把官能团化学与波谱证据联系起来，提出一个结构或一整条合成路线。
Typical Combined 190 problems begin with a target molecule and a starting material, often with both aliphatic and aromatic features. You will be asked to plan a synthesis in three to five steps, identifying reagents, conditions, and intermediate products. Then you receive spectral data – IR, MS, and NMR – to confirm each intermediate or the final product.
典型的组合190问题给出一个目标分子和一个起始原料，往往同时含有脂肪族和芳香族特征。题目会要求你设计三到五步的合成，指明试剂、条件和中间产物。接着你会得到谱图数据——IR、MS和NMR——用以确证每一个中间体或最终产物。
2. Functional Group Interconversions | 官能团互变
At the heart of any synthetic route lies the ability to convert one functional group into another. Edexcel expects familiarity with the interconversion chart that links alkanes, haloalkanes, alcohols, aldehydes, ketones, carboxylic acids, esters, amines, nitriles and amides. Key transformations include nucleophilic substitution, elimination, oxidation, reduction, esterification, and hydrolysis.
任何合成路线的核心都是官能团之间的相互转化。Edexcel要求你熟悉连接烷烃、卤代烷、醇、醛、酮、羧酸、酯、胺、腈和酰胺的互变图表。关键转化包括亲核取代、消除、氧化、还原、酯化和水解。
For example, a primary alcohol can be oxidised to an aldehyde using acidified potassium dichromate(VI) with distillation, or fully oxidised to a carboxylic acid under reflux. A haloalkane can be converted to a nitrile by heating with KCN in ethanol, lengthening the carbon chain by one atom. Reduction of a nitrile using LiAlH₄ in dry ether yields a primary amine.
例如，伯醇可以用酸化重铬酸钾(VI)在蒸馏条件下氧化成醛，或在回流条件下完全氧化成羧酸。卤代烷与KCN的乙醇溶液共热可转化为腈，使碳链增加一个原子。用LiAlH₄在无水乙醚中还原腈则得到伯胺。
3. Key Reaction Mechanisms | 关键反应机理
Combined 190 often probes understanding of mechanism: curly arrows, dipoles, and transition states. The core mechanisms include SN1 and SN2 for haloalkanes, electrophilic addition in alkenes, electrophilic substitution in arenes (nitration, Friedel–Crafts), nucleophilic addition in carbonyls, and nucleophilic addition–elimination in acyl chlorides and esters.
组合190常考查对反应机理的理解：弯箭头、偶极和过渡态。核心机理包括卤代烷的SN1和SN2、烯烃的亲电加成、芳烃的亲电取代（硝化、傅克反应）、羰基的亲核加成，以及酰氯和酯的亲核加成-消除。
When drawing SN2, remember the backside attack leading to inversion of configuration; the transition state is a single step with a pentacoordinate carbon. In contrast, SN1 involves a planar carbocation intermediate that can be attacked from either face, potentially giving racemisation. For benzene chemistry, the electrophile must be generated first – NO₂⁺ from a nitrating mixture of concentrated HNO₃ and H₂SO₄, or CH₃⁺ from CH₃COCl and AlCl₃.
画出SN2机理时，记住背后进攻导致构型翻转；过渡态是单一步骤，含五配位碳。而SN1则经历平面碳正离子中间体，可被两面进攻，可能导致外消旋化。对于苯的化学，必须先产生亲电试剂——硝化混酸（浓HNO₃和浓H₂SO₄）产生NO₂⁺，或由CH₃COCl和AlCl₃产生CH₃⁺。
4. Designing Synthetic Routes | 设计合成路线
Synthesis design is a central plank of Combined 190. Always work backwards from the target molecule, identifying disconnections at functional groups. Consider how each bond could be formed: a C–C bond might come from a nitrile extension or a Friedel–Crafts alkylation; a C–O bond could arise from esterification or Williamson ether synthesis.
合成设计是组合190的核心组成部分。始终从目标分子倒推，在官能团处进行切断。思考每根键如何形成：C–C键可能来自腈基延伸或傅克烷基化；C–O键可由酯化或威廉姆逊醚合成产生。
Ask yourself: is the carbon skeleton correct? If you need to add carbons, introduce a nitrile or use a Grignard reagent (though Grignard is not explicitly required in Edexcel, you can use KCN for chain extension). If the target contains a chiral centre, discuss stereochemical implications and reagent selectivity. Always check chemoselectivity: an oxidizing agent will attack an alcohol but not an alkane; a reducing agent like NaBH₄ reduces carbonyls but not esters under standard conditions.
问自己：碳骨架是否正确？如果需要增碳，可以引入腈或使用格氏试剂（虽然Edexcel未明确要求格氏试剂，可用KCN增长碳链）。如果目标分子含有手性中心，讨论立体化学影响和试剂的选择性。务必检查化学选择性：氧化剂会进攻醇而不进攻烷烃；还原剂如NaBH₄在标准条件下还原羰基而不还原酯。
5. Practical Techniques in Synthesis | 合成中的实验技术
Combined 190 questions frequently incorporate practical methods. You need to describe heating under reflux for oxidation or esterification, distillation to isolate aldehydes, separating funnels for extraction, and recrystallisation or chromatography for purification. Melting point determination and thin-layer chromatography (TLC) are used to check purity.
组合190问题常融入实验方法。你需要描述用于氧化或酯化的回流加热、用于分离醛的蒸馏、萃取用的分液漏斗，以及用于纯化的重结晶或色谱法。通过测定熔点和薄层色谱（TLC）检查纯度。
Safety and yield are also assessed. State that anti-bumping granules prevent bumping during boiling, and that a calcium chloride drying tube may be needed to exclude moisture when handling water-sensitive reagents like acyl chlorides. Calculate percentage yield and atom economy; comment on the environmental acceptability of by-products.
安全和产率同样被考核。说明防沸石防止暴沸，处理酰氯等水敏试剂时可能需要氯化钙干燥管以隔绝湿气。计算百分比产率和原子经济性；评估副产物对环境的影响。
6. Introduction to Spectroscopic Analysis | 光谱分析导论
Once the synthetic route is laid out, Combined 190 turns to spectral identification. Modern Edexcel papers provide IR, mass spectrum, ¹³C NMR and ¹H NMR data for an unknown compound or an intermediate. You must use this data to deduce functional groups, molecular formula, and eventually the full structure.
在拟定好合成路线之后，组合190转向光谱鉴定。现代Edexcel试卷会给出未知物或中间体的红外、质谱、碳-13核磁共振和氢核磁共振数据。你必须利用这些数据推断官能团、分子式，最终得出完整结构。
Each spectroscopic technique gives a piece of the puzzle. IR identifies bond vibrations (functional groups); MS gives molecular ion peak and fragmentation pattern; ¹³C NMR tells the number of chemically distinct carbon environments; ¹H NMR reveals proton environments, integration, and splitting, giving the final confirmation of the carbon-hydrogen framework.
每一种光谱技术提供拼图的一部分。红外确认键的振动（官能团）；质谱给出分子离子峰和碎裂规律；碳-13核磁共振显示化学不等价碳环境的数目；氢核磁共振揭示质子环境、积分和裂分，最终确认碳氢骨架。
7. Infrared (IR) Spectroscopy | 红外光谱
are reported in wavenumber (cm⁻¹). In Edexcel Combined 190, you must recognise the broad O–H stretch in alcohols (3200–3550) and carboxylic acids (2500–3300, very broad), the sharp C=O stretch (1680–1750) with variations for aldehydes, ketones, acids and esters, and the C–O stretch (1000–1300). N–H stretches appear around 3300–3500 in amines and amides.
红外光谱检测分子振动。吸收峰以波数（cm⁻¹）报告。在Edexcel组合190中，你必须识别醇的宽O–H伸缩（3200–3550），羧酸极宽的O–H伸缩（2500–3300），以及不同化合物中C=O伸缩的尖锐峰（1680–1750）——醛、酮、酸和酯各有细微差异，还有C–O伸缩（1000–1300）。氨基和酰胺的N–H伸缩出现在3300–3500附近。
ctrum molecular ion can confirm whether it is an aldehyde or ketone. An absence of broad O–H yet presence of C=O suggests an ester or ketone. If you see C=C around 1620–1680 cm⁻¹, think of an alkene or arene.
始终把红外峰与其他数据关联。1720 cm⁻¹的强峰表明羰基，但只有质谱的分子离子峰才能确认是醛还是酮。没有宽O–H峰而有C=O峰意味着酯或酮。若在1620–1680 cm⁻¹处看到C=C伸缩，则考虑烯烃或芳烃。
8. Mass Spectrometry (MS) | 质谱
In electron impact mass spectrometry, the molecule is bombarded with high-energy electrons, producing a radical cation M⁺⁺ that often fragments. The highest m/z peak (ignoring small isotope peaks) gives the molecular ion, indicating relative molecular mass. For Edexcel Combined 190, you may need to deduce a molecular formula from the M peak and fragment patterns.
在电子轰击质谱中，分子被高能电子轰击产生自由基阳离子 M⁺⁺，并常发生碎裂。最高的质荷比峰（忽略小的同位素峰）给出分子离子，指示相对分子质量。Edexcel组合190中，你可能需要根据M峰和碎裂模式推断分子式。
/z = 57 suggests butyl. Halogen patterns are diagnostic: chlorine gives a 3:1 ratio for M and M+2 peaks; bromine gives a 1:1 ratio.
常见碎片包括丢失甲基（15）、乙基（29）、OH（17）或CO（28）。m/z = 43的峰暗示丙基或乙酰基碎片；m/z = 57指示丁基。卤素的同位素模式具有诊断价值：氯给出M和M+2峰的3:1比例；溴给出1:1的比例。
9. Carbon-13 NMR Spectroscopy | 碳-13核磁共振波谱
¹³C NMR provides the number of chemically non-equivalent carbon environments. Each distinct carbon gives a single peak, chemically shifted according to its electronic surroundings. Combined 190 expects you to interpret ¹³C shifts: 5–40 for alkyl carbons, 50–90 for carbons attached to oxygen (C–O), 100–150 for alkene/arene carbons, and 160–220 for carbonyl carbons (esters and acids at the lower end, aldehydes and ketones at the higher end).
碳-13核磁共振波谱提供化学不等价碳环境的数目。每个独特的碳给出一个单峰，其化学位移依赖于周围的电子环境。组合190要求你解析碳谱位移：烷基碳在5–40，连氧碳（C–O）在50–90，烯烃/芳烃碳在100–150，羰基碳在160–220（酯和酸在低端，醛和酮在高端）。
Count the number of ¹³C peaks carefully: it directly limits the symmetry of the molecule. If you have a molecular formula C₈H₈O₂ and only four ¹³C peaks, the molecule must be highly symmetric – perhaps a para-disubstituted benzene like 1,4-dimethoxybenzene. Use the peak count to eliminate structural isomers.
仔细数好碳谱峰的数量：它直接限定了分子的对称性。如果你的分子式是C₈H₈O₂而只有四个碳峰，说明该分子高度对称——也许是一个对位二取代苯，比如1,4-二甲氧基苯。利用峰数排除结构异构体。
10. Proton NMR Spectroscopy | 质子核磁共振波谱
¹H NMR is the most information-rich technique in Combined 190. Each signal is defined by chemical shift (δ, ppm), integration (number of hydrogens), and splitting pattern (multiplicity). For Edexcel, focus on shifts: alkyl H 0.7–2.0, H–C–O 3.0–4.5, alkene H 4.5–6.5, aromatic H 6.5–8.0, aldehyde H 9.5–10.0, carboxylic acid O–H 10–12, alcohol O–H variable, often 1–5 but exchangeable.
氢核磁共振是组合190中信息最丰富的手段。每个信号由化学位移（δ, ppm）、积分（氢原子数）和裂分模式（多重性）定义。Edexcel重点掌握位移：烷基氢0.7–2.0，连氧碳上的氢（H–C–O）3.0–4.5，烯烃氢4.5–6.5，芳氢6.5–8.0，醛氢9.5–10.0，羧酸O–H在10–12，醇O–H变化较大，通常1–5但可交换。
r the CH₃ and a quartet for the CH₂. Watch for overlapping signals and exchangeable protons (OH, NH) that may appear as broad singlets or disappear in D₂O shake.
裂分遵循n+1规则：一个有n个等价邻位的氢会被裂分成n+1个峰。因此与CH₂相邻的CH₃对CH₃表现为三重峰（n=2, 2+1=3），CH₂则被裂分为四重峰。注意信号重叠和可交换质子（OH、NH），它们可能表现为宽单峰或在D₂O交换后消失。
11. Combined Spectra Problem-Solving | 综合谱图问题解析
Combined 190 exam questions typically present all four spectra in a single scenario. A systematic approach is essential. Step 1: Use MS to get molecular mass and formula, and check for halogen or nitrogen. Step 2: IR to identify key functional groups. Step 3: ¹³C NMR to count distinct carbons and infer symmetry. Step 4: ¹H NMR to map the hydrogen frameworks and assemble fragments. Finally, propose a structure consistent with all data.
组合190试题通常在同一情境下给出四种谱图。系统性的解题思路至关重要。第一步：用质谱获取分子质量和分子式，并检查卤素或氮。第二步：用红外确定关键官能团。第三步：用碳谱计数不等价碳推测对称性。第四步：用氢谱描绘氢原子框架并把碎片拼装起来。最后提出与所有数据一致的结构。
When a mismatch arises, check for acidic protons that did not appear on ¹H, or reassign IR carbonyl peaks. Always verify that the proposed structure can be the product of your synthetic route. If the spectra match an ester, ensure your steps lead to an ester and not a ketone. This loop between synthesis and analysis is the essence of Combined 190.
若出现矛盾，检查是否有酸性氢未在氢谱上显现，或重新归属红外羰基峰。务必验证所提出的结构能够是你合成路线的产物。如果谱图相符的是一个酯，那么要确保你的步骤最终生成的是酯而非酮。这种在合成和分析间的闭环是组合190的精髓。
12. Exam Tips for Combined 190 | 组合190考试技巧
In the Edexcel exam, Combined 190-style questions can carry 12–20 marks. Allocate time proportionally: plan the synthesis (4–5 min), draw the route clearly with reagents and conditions, then analyse spectra (8–10 min). Always label spectra: mark the molecular ion on MS, circle IR diagnostic peaks, and comment on splitting in ¹H NMR.
在Edexcel考试中，组合190风格的题目可能占12–20分。按比例分配时间：规划合成（4–5分钟），清晰画出路线并注明试剂与条件，然后分析谱图（8–10分钟）。始终标注谱图：在质谱上标出分子离子峰，在红外上圈出诊断峰，在氢谱中注释裂分。
Common pitfalls include forgetting to include lone pairs on nucleophiles in mechanisms, drawing impossible pentavalent carbons in transition states, misinterpreting integration ratios, and neglecting stereochemistry when a chiral centre is formed. Regular practice with the Edexcel data booklet chemical shift tables is indispensable. Speed and accuracy come from revisiting multiple Combined 190 problems until the workflow becomes automatic.
常见失误包括：机理中漏画亲核试剂上的孤对电子、在过渡态绘出不可能的五价碳、错误解释积分比例、以及当生成手性中心时忽略立体化学。经常查阅Edexcel数据手册中的化学位移表是不可或缺的。速度和准确度来自反复演练多个组合190问题，直至解题流程自动化。
Published by TutorHao | Chemistry Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图