Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

15. Analytical Techniques:IR, NMR, Mass Spect

1H NMR:Spin-Splitting Patterns

Organic Chemistry

15. Analytical Techniques:IR, NMR, Mass Spect

1H NMR:Spin-Splitting Patterns

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Problem 61f

Textbook Question

Draw the signal for the following multiplicities. What is the ratio of peaks within each signal?
(f) septet

Verified step by step guidance

Understand the concept of multiplicity in NMR spectroscopy. Multiplicity refers to the splitting of NMR signals into multiple peaks due to interactions with neighboring non-equivalent protons. The number of peaks is determined by the n+1 rule, where n is the number of neighboring protons.

Identify the multiplicity given in the problem. Here, we are dealing with a 'septet'. According to the n+1 rule, a septet indicates that there are 6 neighboring protons (n = 6), as 6 + 1 = 7 peaks.

Determine the ratio of peaks within a septet. The ratio of peaks in a septet follows Pascal's triangle, which for a septet is 1:6:15:20:15:6:1. This means the intensity of the peaks will follow this pattern.

Draw the signal for a septet. When sketching the septet, ensure that there are seven peaks with the central peak being the tallest, and the heights of the peaks decreasing symmetrically as you move away from the center, following the ratio 1:6:15:20:15:6:1.

Review the concept of coupling constants. The distance between the peaks in a septet is determined by the coupling constant (J value), which is a measure of the interaction between the coupled protons. This is important for accurately representing the septet in an NMR spectrum.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

NMR Multiplicity

NMR multiplicity refers to the splitting of NMR signals into multiple peaks due to interactions between neighboring non-equivalent hydrogen atoms. The number of peaks in a signal is determined by the n+1 rule, where n is the number of neighboring hydrogens. This splitting provides insights into the number of adjacent hydrogens and the structure of the molecule.

Septet in NMR

A septet in NMR spectroscopy is a signal that splits into seven peaks. This occurs when a hydrogen atom is adjacent to six equivalent hydrogen atoms, following the n+1 rule (6+1=7). The septet pattern is often seen in molecules with symmetrical environments, such as isopropyl groups, where the central hydrogen is influenced by six equivalent hydrogens.

Pascal's Triangle and Peak Ratios

Pascal's Triangle is used to determine the intensity ratios of peaks in NMR multiplets. For a septet, the peak ratio follows the 1:6:15:20:15:6:1 pattern, derived from the seventh row of Pascal's Triangle. These ratios reflect the probability of different spin states of neighboring hydrogens, helping to interpret the relative intensities of the peaks in the septet.

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