Textbook Question
Identify each of the following compounds from its molecular formula and its IR and 1H NMR spectra.
d. C4H8O2
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Ch. 14 - NMR Spectroscopy
Bruice8th EditionOrganic ChemistryISBN: 9780135213711
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Table of contents
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 1)31
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 2)65
- Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry84
- Ch. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and Structure183
- Ch. 4 - Isomers: The Arrangement of Atoms in Space121
- Ch. 5 - Alkenes: Structure, Nomenclature, and an Introduction to Reactivity • Thermodynamics and Kinetics83
- Ch. 6 - The Reactions of Alkenes • The Stereochemistry of Addition Reactions175
- Ch. 7 - The Reactions of Alkynes • An Introduction to Multistep Synthesis119
- Ch. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of Benzene148
- Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides212
- Ch. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds131
- Ch. 11 - Organometallic Compounds60
- Ch. 12 - Radicals90
- Ch. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis Spectroscopy62
- Ch. 14 - NMR Spectroscopy95
- Ch. 15 - Reactions of Carboxylic Acids and Carboxylic Acid Derivatives123
- Ch. 16 - Reactions of Aldehydes and Ketones • More Reactions of Carboxylic Acid Derivatives141
- Ch. 17 - Reactions at the Alpha-Carbon101
- Ch. 18 - Reactions of Benzene and Substituted Benzenes144
- Ch. 19 - More About Amines • Reactions of Heterocyclic Compounds49
- Ch. 20 - The Organic Chemistry of Carbohydrates80
- Ch. 21 - Amino Acids, Peptides, and Proteins57
- Ch. 22 - Catalysis in Organic Reactions and in Enzymatic Reactions35
- Ch. 23 - The Organic Chemistry of the Coenzymes—Compounds Derived from Vitamins1
- Ch. 28 - Pericyclic Reactions58
Chapter 15, Problem 63b
Identify each of the following compounds from its molecular formula and its IR and 1H NMR spectra:
b. C6H12O2
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Verified step by step guidance1
Step 1: Analyze the molecular formula (C6H12O2) to determine the degree of unsaturation. Use the formula: \( \text{Degree of Unsaturation} = rac{2C + 2 - H + N - X}{2} \), where \( C \) is the number of carbons, \( H \) is the number of hydrogens, \( N \) is the number of nitrogens, and \( X \) is the number of halogens. For this compound, calculate \( \text{Degree of Unsaturation} = rac{2(6) + 2 - 12}{2} = 1 \), indicating one double bond or a ring.
Step 2: Examine the IR spectrum. Look for characteristic absorption bands. For example, a strong, broad peak around 3200-3600 cm\(^{-1}\) indicates an O-H group (alcohol or carboxylic acid). A sharp peak near 1700 cm\(^{-1}\) suggests a carbonyl group (C=O). Identify these functional groups based on the observed peaks.
Step 3: Analyze the \( ^1H \) NMR spectrum. Look for the number of signals, their chemical shifts, integration values, and splitting patterns. For example, a singlet around 9-10 ppm suggests an aldehyde proton, while a peak around 2-4 ppm could indicate protons adjacent to an electronegative atom (e.g., oxygen). Use the integration values to determine the relative number of protons contributing to each signal.
Step 4: Combine the information from the IR and \( ^1H \) NMR spectra with the molecular formula. For example, if the IR spectrum shows a carbonyl group and the \( ^1H \) NMR spectrum indicates protons near oxygen, the compound could be an ester or a carboxylic acid. Use the splitting patterns and chemical shifts to refine the structure further.
Step 5: Propose a structure that matches the molecular formula, degree of unsaturation, and spectral data. Verify that the structure accounts for all observed peaks in the IR and \( ^1H \) NMR spectra, as well as the molecular formula (C6H12O2).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Molecular Formula Interpretation
The molecular formula provides essential information about the number and types of atoms in a compound. For C6H12O2, it indicates the presence of six carbon atoms, twelve hydrogen atoms, and two oxygen atoms. Understanding how to interpret this formula is crucial for deducing the possible structure and functional groups present in the compound.
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Infrared (IR) Spectroscopy
IR spectroscopy is a technique used to identify functional groups in a molecule based on the absorption of infrared light. Different bonds absorb characteristic wavelengths, allowing chemists to infer the presence of specific functional groups, such as alcohols, esters, or carboxylic acids, which may be present in C6H12O2. Analyzing the IR spectrum helps in confirming the molecular structure.
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Proton Nuclear Magnetic Resonance (1H NMR) Spectroscopy
1H NMR spectroscopy provides information about the hydrogen atoms in a molecule, revealing their environment and connectivity. The chemical shifts, splitting patterns, and integration of peaks in the NMR spectrum can indicate the number of hydrogen atoms attached to different carbon atoms and help identify the structure of C6H12O2. This technique is essential for confirming the identity of organic compounds.
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Related Practice
Textbook Question
The 1H NMR spectra of three isomers with molecular formula C7H14O are shown here. Which isomer produces which spectrum?
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Textbook Question
An alkyl halide reacts with an alkoxide ion to form a compound whose 1H NMR spectrum is shown here. Identify the alkyl halide and the alkoxide ion. (Hint: See Section 9.15.)
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Textbook Question
The 1H NMR spectrum of 2-propen-1-ol is shown here. Indicate the protons in the molecule that are responsible for each of the signals in the spectrum.
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Textbook Question
Draw a splitting diagram for the Hb proton if Jbc = 10 and Jba = 5.
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Textbook Question
Would it be better to use 1H NMR or 13C NMR spectroscopy to distinguish 1-butene, cis-2-butene, and 2-methylpropene? Explain your answer.
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