Textbook Question
How many signals are produced by each of the following compounds in its
b. 13C NMR spectrum?
2.
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15. Analytical Techniques:IR, NMR, Mass Spect
Carbon NMR
5:11 minutesProblem 69c
Textbook Question
Sketch the following spectra that would be obtained for 2-chloroethanol:
c. The 13C NMR spectrum.
Verified step by step guidance1
Identify the structure of 2-chloroethanol (ClCH2CH2OH). It contains two carbon atoms: one bonded to a chlorine atom and the other bonded to a hydroxyl group. These two carbons are chemically non-equivalent, meaning they will produce distinct signals in the 13C NMR spectrum.
Determine the chemical environment of each carbon atom. The carbon bonded to the chlorine atom (ClCH2-) is deshielded due to the electronegativity of chlorine, resulting in a downfield shift. The carbon bonded to the hydroxyl group (-CH2OH) is also deshielded, but to a lesser extent than the chlorine-bonded carbon.
Predict the approximate chemical shift range for each carbon. The carbon bonded to chlorine typically appears in the range of 40-80 ppm, while the carbon bonded to the hydroxyl group typically appears in the range of 50-70 ppm. These ranges are approximate and depend on the solvent and other experimental conditions.
Consider the splitting pattern. In 13C NMR, splitting due to coupling with directly bonded hydrogens (1H) is often not observed because broadband decoupling is typically used. Therefore, each carbon will appear as a single peak.
Sketch the spectrum. Represent the two distinct peaks on the x-axis (chemical shift in ppm) with their approximate positions based on the predicted ranges. Label the peak at the lower ppm value as the carbon bonded to the hydroxyl group (-CH2OH) and the peak at the higher ppm value as the carbon bonded to chlorine (ClCH2-).
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Video duration:
5mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Nuclear Magnetic Resonance (NMR) Spectroscopy
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 (13C), to provide information about the number and environment of carbon atoms in a molecule. The resulting spectrum displays peaks corresponding to different carbon environments, allowing chemists to infer structural details.
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General NMR Features
Chemical Shifts in 13C NMR
Chemical shifts in 13C NMR refer to the variation in resonance frequency of carbon nuclei due to their electronic environment. Each unique carbon atom in a molecule will resonate at a different frequency, which is measured in parts per million (ppm). The position of these peaks on the spectrum provides insight into the types of functional groups and the overall structure of the compound.
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Integration and Peak Multiplicity
In 13C NMR, integration refers to the area under the peaks, which correlates with the number of equivalent carbon atoms contributing to that signal. Peak multiplicity, influenced by neighboring hydrogen atoms, indicates the number of adjacent protons and helps deduce the connectivity of the carbon atoms. Understanding these aspects is crucial for interpreting the spectrum of 2-chloroethanol accurately.
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