Textbook Question
Given the ¹H NMR spectrum and the molecular formula, suggest a structure for each molecule. [The IR spectrum suggests the presence of two C=O bonds.]
(b) <IMAGE>
3
views
Ch. 15 - Structural Identification II: Nuclear Magnetic Resonance Spectroscopy
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471
Not the one you use?Change textbookSelect a different textbook
Table of contents
- Ch. 2 - General Chemistry Translated: Finding the Electrons114
- Ch. 3 - Alkanes and Cycloalkanes: Properties and Conformational Analysis109
- Ch. 4 - Acids and Bases: Electron Flow144
- Ch. 5 - Chemical Reaction Analysis: Thermodynamics and Kinetics118
- Ch. 6 - Stereoisomerism: Arrangement of Atoms in Space112
- Ch. 7 - Principles of Green (Organic) Chemistry3
- Ch. 8 - Alkenes I: Properties and Electrophilic Additions158
- Ch. 9 - Alkenes II: Oxidation and Reduction150
- Ch. 10 - Alkynes: Electrophilic Addition and Redox Reactions101
- Ch. 11 - Properties and Synthesis of Alkyl Halides: Radical Reactions108
- Ch. 12 - Substitution and Elimination: Reactions of Haloalkanes172
- Ch. 13 - Alcohols, Ethers and Related Compounds: Substitution and Elimination239
- Ch. 14 - Structural Identification I: Infrared Spectroscopy and Mass Spectrometry54
- Ch. 15 - Structural Identification II: Nuclear Magnetic Resonance Spectroscopy93
- Ch. 16 - Metals in Organic Chemistry48
- Ch. 17 - Carbonyl Addition Reactions: Aldehydes and Ketones45
- Ch. 18 - Nucleophilic Acyl Substitution I: Carboxylic Acids18
- Ch. 19 - Nucleophilic Acyl Substitution II: Carboxylic Acid Derivatives39
- Ch. 20 - Enolates: Carbonyl Addition and Substitution13
- Ch. 21 - Conjugated Systems I: Stability and Addition Reactions56
- Ch. 22 - Conjugated Systems II: Pericyclic Reactions54
- Ch. 23 - Benzene I: Aromatic Stability and Substitution Reactions64
- Ch. 24 - Benzene II: Reactions Influenced by the Aromatic Ring62
- Ch. 25 - Amines: Structure, Reactions, and Synthesis27
- Ch. 26 - Amino Acids, Proteins, and Peptide Synthesis9
- Ch. 27 - Carbohydrates, Nucleic Acids, and Lipids54
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
All textbooks
Mullins 1st EditionCh. 15 - Structural Identification II: Nuclear Magnetic Resonance SpectroscopyProblem 78a
Mullins 1st EditionCh. 15 - Structural Identification II: Nuclear Magnetic Resonance SpectroscopyProblem 78aChapter 14, Problem 78a
Given the ¹H NMR spectrum and the molecular formula, suggest a structure for each molecule. [The IR spectrum suggests the presence of two C=O bonds.]
(a) Important IR bands (cm ⁻ ¹) : 1728, 1708 [Note: The pKₐ of this molecule is around 10.]
<IMAGE>
Verified step by step guidance1
Examine the IR spectrum data: The presence of two C=O bonds is indicated by the IR bands at 1728 cm⁻¹ and 1708 cm⁻¹. These are characteristic of carbonyl groups, such as ketones or aldehydes.
Consider the molecular formula and the pKₐ value: A pKₐ around 10 suggests the presence of an acidic hydrogen, possibly indicating a carboxylic acid or a similar functional group.
Analyze the ¹H NMR spectrum: Look for signals that correspond to protons near the carbonyl groups. This can help identify the specific environment of the protons and provide clues about the structure.
Combine the IR and NMR data: Use the information from both spectra to hypothesize possible structures. The presence of two carbonyl groups and an acidic hydrogen suggests a dicarboxylic acid or a similar compound.
Propose a structure: Based on the spectral data and the molecular formula, suggest a structure that fits all the given information, ensuring that it accounts for the two C=O bonds and the acidic hydrogen.
Verified video answer for a similar problem:
This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
6mWas this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
¹H NMR Spectroscopy
¹H NMR (Proton Nuclear Magnetic Resonance) spectroscopy is a technique used to determine the structure of organic compounds by analyzing the magnetic environment of hydrogen atoms. It provides information about the number of hydrogen atoms, their chemical environment, and how they are connected within a molecule. Peaks in the spectrum correspond to different hydrogen environments, and their splitting patterns can indicate neighboring hydrogen atoms.
Recommended video:
Guided course
10:06
General NMR Features
IR Spectroscopy and Functional Groups
Infrared (IR) spectroscopy is used to identify functional groups in a molecule by measuring the absorption of infrared light, which causes molecular vibrations. Specific absorption bands correspond to different functional groups. In this question, the presence of two C=O bonds is indicated by IR bands at 1728 and 1708 cm⁻¹, suggesting the presence of carbonyl groups, such as ketones or aldehydes, which are crucial for determining the molecular structure.
Recommended video:
Guided course
02:36Identifying Functional Groups
pKₐ and Acid-Base Properties
The pKₐ value of a molecule indicates the acidity of a hydrogen atom within the molecule, reflecting how easily it can donate a proton. A pKₐ around 10 suggests the presence of a moderately acidic hydrogen, often associated with functional groups like carboxylic acids or phenols. Understanding the pKₐ helps in identifying possible acidic sites in the molecule, which is essential for proposing a plausible structure.
Recommended video:
2:07Acid-Base Properties of Nitrogen Heterocycles Concept 1
Related Practice
Textbook Question
In the lab, ¹H NMR is often used to verify that a reaction has worked as expected by comparing the product spectrum with what is expected. Given the ¹H NMR of the reactant shown, draw the spectrum you'd expect to see of the product that results.
<IMAGE>
2
views
Textbook Question
A graduate student ran a reaction that produced a mixture of the following two compounds. After painstaking purification, she is able to separate the two compounds. Using ¹H NMR, how can she determine which diastereomer is in which separated sample?
1
views
Textbook Question
For the compound shown, produce a table of the shift, integration, and multiplicity of each peak you would expect to see in a ¹H NMR spectrum.
2
views
Textbook Question
(a) Using the ¹H NMR spectra, identify the reactants and product for this reaction.
<IMAGE>
1
views
Textbook Question
The spectral data below are presented in a manner similar to what you would find in a chemistry research journal. Identify the structure for each set of data.
(c) C₇H₁₄O₂ : ¹H NMR: δ 0.91 (3H, t, J = 7.0 Hz), 1.11 (6H, d, J = 7.0 Hz), 1.82 (2H, sextet), 2.40 (1H, sept, J = 7.0 Hz), 4.14 (2H, t, J = 7.1 Hz); IR (cm ⁻¹) : 1745, 1200
2
views