Textbook Question
The following 1H NMR spectra are for four compounds, each with molecular formula of C6H12O2. Identify the compounds.
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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 75
When compound A (C5H12O) is treated with HBr, it forms compound B (C5H11Br). The 1H NMR spectrum of compound A has a 1H singlet, a 3H doublet, a 6H doublet, and two 1H multiplets. The 1H NMR spectrum of compound B has a 6H singlet, a 3H triplet, and a 2H quartet. Identify compounds A and B.
Verified step by step guidance1
Analyze the molecular formula of compound A (C5H12O). This indicates it is an alcohol, as it contains one oxygen atom and follows the general formula for alcohols (CnH2n+2O).
Interpret the 1H NMR spectrum of compound A: The singlet (1H) suggests a hydroxyl (-OH) group. The doublets (3H and 6H) indicate the presence of methyl groups adjacent to a chiral center or other splitting-inducing groups. The two multiplets (1H each) suggest protons on a carbon adjacent to other carbons with hydrogens.
Consider the reaction with HBr: Alcohols react with HBr to form alkyl bromides via substitution. The hydroxyl group (-OH) is replaced by a bromine atom (-Br). This reaction often proceeds via an SN1 or SN2 mechanism depending on the structure of the alcohol.
Analyze the 1H NMR spectrum of compound B (C5H11Br): The 6H singlet suggests two equivalent methyl groups attached to the same carbon. The 3H triplet and 2H quartet indicate an ethyl group (-CH2CH3) is present in the molecule.
Combine the information: Compound A is likely tert-pentyl alcohol (2-methyl-2-butanol), as its structure matches the NMR data. When treated with HBr, it forms compound B, tert-pentyl bromide (2-methyl-2-butyl bromide), which also matches the NMR data for the product.
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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 provides information about the number of hydrogen atoms in different environments, indicated by peaks in the spectrum. The splitting patterns (singlets, doublets, triplets, etc.) reveal the number of neighboring hydrogen atoms, which helps in deducing the connectivity of atoms within the molecule.
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General NMR Features
Substitution Reactions
Substitution reactions involve the replacement of one atom or group in a molecule with another. In this case, the treatment of compound A with HBr results in the substitution of a hydroxyl group (-OH) with a bromine atom (-Br). Understanding the mechanism of substitution, whether it is nucleophilic or electrophilic, is crucial for predicting the structure of the resulting compound B.
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01:34Recognizing Substitution Reactions.
Molecular Formula and Structure
The molecular formula provides essential information about the number and types of atoms in a compound. For compounds A (C5H12O) and B (C5H11Br), analyzing the molecular formula helps in deducing their structures. The presence of functional groups, such as alcohols and alkyl halides, influences the chemical behavior and spectral characteristics, which are critical for identifying the compounds based on their NMR data.
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02:17How to use IHD with molecular formula.
Related Practice
Textbook Question
How many signals are produced by each of the following compounds in its
a. 1H NMR spectrum?
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Textbook Question
The following 1H NMR spectra are for four compounds, each with molecular formula of C6H12O2. Identify the compounds.
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Textbook Question
Identify each of the following compounds from its molecular formula and its IR and 1H NMR spectra:
b.C6H14O
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Textbook Question
Identify the compound with molecular formula C6H10O that gives the following DEPT 13C NMR spectrum:
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Textbook Question
Calculate the amount of energy (in calories) required to flip an 1H nucleus in an NMR spectrometer that operates at 300 MHz.
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