amazon.co.ukC4: Organic Synthesis and Spectroscopic Analysis
¹H and ¹³C NMR spectroscopy, Infrared spectroscopy, High-resolution Mass Spectrometry, synthetic routes.
📋 Key Definitions and Core Concepts
Chemical Shift (δ): Resonant frequency position relative to TMS standard at δ = 0 ppm in ppm.
Spin-Spin Splitting: (n+1) rule: proton signal split into n+1 peaks by n non-equivalent adjacent protons.
🔍 Key Principles & Specification Requirements
- IR key absorptions: O-H alcohol (broad 3200-3600 cm⁻¹), O-H acid (very broad 2500-3300 cm⁻¹), C=O carbonyl (sharp 1680-1750 cm⁻¹).
- ¹³C NMR: number of distinct signals = number of unique carbon environments.
- High-resolution MS: accurate m/z to 4 decimal places distinguishes compounds with same integer mass.
💡 Worked Example Question
Exam-Style Question
Question:
Identify C₃H₆O₂ showing IR 1715 cm⁻¹, broad 2500-3300 cm⁻¹, ¹H NMR triplet δ 1.1 (3H), quartet δ 2.4 (2H), singlet δ 11.5 (1H).
Model Solution & Mark Scheme:
1. IR: 1715 cm⁻¹ (C=O) + 2500-3300 cm⁻¹ (acid O-H) => carboxylic acid (-COOH). 2. ¹H NMR: δ 11.5 singlet is -COOH proton. 3. Triplet δ 1.1 (3H) and quartet δ 2.4 (2H) indicates ethyl group CH₃CH₂-. Structure: Propanoic acid (CH₃CH₂COOH).
❓ Practice Questions & Mark Schemes
Q1: Why is TMS used as NMR standard?
Show Model Answer
Answer: Single sharp peak at δ = 0 ppm, inert, non-toxic, volatile (easily evaporated).
Q2: Describe the D₂O shake in ¹H NMR.
Show Model Answer
Answer: D₂O exchanges with labile -OH and -NH protons (R-OH + D₂O → R-OD + HOD), causing their signals to disappear from the spectrum.
🎬 Video Resources
- Organic Synthesis and Spectroscopic Analysis - Overview -- YouTube Search
- Organic Synthesis and Spectroscopic Analysis - Exam Questions -- YouTube Search
📄 Past Papers & Exam Resources
- AQA A-Level - Past Papers -- AQA
- Edexcel A-Level - Past Papers -- Edexcel
- OCR A-Level - Past Papers -- OCR
🔗 Further Reading & Resources
- Physics & Maths Tutor -- Free notes, worksheets, and past paper questions by topic
- Dr Frost Maths -- Free resources, slides, and interactive questions
- BBC Bitesize -- BBC Bitesize revision resources