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

Carbon NMR

Organic Chemistry

15. Analytical Techniques:IR, NMR, Mass Spect

Carbon NMR

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4:54 minutes

Problem 28

Textbook Question

The standard ¹³C NMR spectrum of phenyl propanoate is shown here. Predict the appearance of the DEPT-90 and DEPT-135 spectra.
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Verified step by step guidance

Step 1: Analyze the standard 13C NMR spectrum provided. Each peak corresponds to a unique carbon environment in phenyl propanoate. The labeled carbons (a, b, c, d, e, f, g, h) represent different chemical environments, including aromatic carbons, ester carbons, and alkyl carbons.

Step 2: Understand DEPT spectra. DEPT-90 shows only CH carbons, while DEPT-135 distinguishes CH and CH3 carbons (positive peaks) from CH2 carbons (negative peaks). Quaternary carbons (no hydrogens attached) do not appear in DEPT spectra.

Step 3: Identify the carbon types in phenyl propanoate. For example, carbon 'd' (carbonyl carbon) is quaternary and will not appear in DEPT spectra. Carbon 'a' (CH3) will appear as a positive peak in DEPT-135. Carbon 'b' (CH2) will appear as a negative peak in DEPT-135. Aromatic carbons (e, f, g, h) are CH carbons and will appear in both DEPT-90 and DEPT-135 as positive peaks.

Step 4: Predict the DEPT-90 spectrum. Only CH carbons will appear, so peaks corresponding to carbons e, f, g, and h will be visible. Other carbons (a, b, c, d) will not appear.

Step 5: Predict the DEPT-135 spectrum. Positive peaks will correspond to CH and CH3 carbons (a, e, f, g, h), while negative peaks will correspond to CH2 carbons (b). Quaternary carbons (d) will not appear.

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Key Concepts

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

NMR Spectroscopy

Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful analytical technique used to determine the structure of organic compounds. It exploits the magnetic properties of certain nuclei, such as carbon-13, to provide information about the number and environment of atoms in a molecule. The resulting spectra reveal details about the molecular framework, including the types of hydrogen and carbon present.

DEPT NMR Techniques

DEPT (Distortionless Enhancement by Polarization Transfer) is a specialized NMR technique that enhances the detection of specific types of carbon atoms in a molecule. DEPT-90 selectively shows only CH (methine) carbons, while DEPT-135 displays CH and CH3 (methyl) carbons as positive signals and CH2 (methylene) carbons as negative signals. These techniques help in distinguishing between different carbon environments and provide clarity in interpreting the carbon skeleton.

Phenyl Propanoate Structure

Phenyl propanoate is an ester formed from phenol and propanoic acid, characterized by a phenyl group attached to a propanoate moiety. Understanding its structure is crucial for predicting NMR spectra, as the arrangement of carbon atoms influences the chemical shifts observed in the DEPT spectra. The presence of aromatic and aliphatic carbons in phenyl propanoate will result in distinct patterns in the DEPT-90 and DEPT-135 spectra.

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Related Practice

Textbook Question

Draw the ¹³C NMR spectrum you would expect to see for each of the molecules shown.

(c)

Textbook Question

How might you use ¹³C NMR spectroscopy to differentiate between the possible ortho, meta, and para products of the electrophilic aromatic substitution reaction shown?

Textbook Question

Sketch the following spectra that would be obtained for 2-chloroethanol:

e. The four parts of a DEPT ¹³C NMR spectrum.

Textbook Question

Identify the compound with molecular formula C₆H₁₀O that gives the following DEPT ¹³C NMR spectrum:

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Textbook Question

Different types of protons and carbons in alkanes tend to absorb at similar chemical shifts, making structure determination difficult. Explain how the ¹³C NMR spectrum, including the DEPT technique, would allow you to distinguish among the following four isomers.

Multiple Choice

How many signals would be expected in the ¹³C NMR spectrum for the following molecule?

Multiple Choice

An alkene/aromatic signal will often appear ~ 160–170 ppm in a ¹³C NMR spectrum. Why?

Textbook Question

How many signals would you expect to see in the 13C NMR of the following compounds? In each case, show which carbon atoms are equivalent in the ¹³C NMR.

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The standard 13C NMR spectrum of phenyl propanoate is shown here. Predict the appearance of the DEPT-90 and DEPT-135 spectra.<IMAGE>

Key Concepts

NMR Spectroscopy

DEPT NMR Techniques

Phenyl Propanoate Structure

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The standard ¹³C NMR spectrum of phenyl propanoate is shown here. Predict the appearance of the DEPT-90 and DEPT-135 spectra.
<IMAGE>