Textbook Question
Identify the peaks in the mass spectrum of octan-4-one that correspond to (b) the McLafferty rearrangement.
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15. Analytical Techniques:IR, NMR, Mass Spect
Mass Spect:Fragmentation
6:37 minutesProblem 45
Textbook Question
Assign the structure based on the mass spectrum and IR spectrum shown.
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Verified step by step guidance1
Examine the mass spectrum to identify the molecular ion peak, which is the peak with the highest m/z value. This peak represents the molecular weight of the compound.
Look for significant peaks in the mass spectrum that could indicate common fragmentations. For example, a peak at m/z 15 could suggest a methyl group, while a peak at m/z 29 could indicate an ethyl group.
Analyze the IR spectrum for characteristic absorption bands. A broad peak around 3300 cm-1 could indicate an O-H or N-H bond, while a sharp peak around 1700 cm-1 could suggest a C=O bond.
Combine the information from both spectra. Use the molecular ion peak to determine the possible molecular formula and the IR spectrum to identify functional groups present in the molecule.
Propose a structure that fits both the mass spectrum and IR spectrum data. Ensure that the proposed structure accounts for all significant peaks and functional groups identified in the spectra.
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6mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Mass Spectrometry
Mass spectrometry is an analytical technique used to measure the mass-to-charge ratio (m/z) of ions. It helps identify the molecular weight and structure of a compound by analyzing the fragmentation pattern. Peaks in the mass spectrum represent different fragments, with the highest m/z peak often corresponding to the molecular ion, indicating the molecular weight of the compound.
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Infrared (IR) Spectroscopy
IR spectroscopy is a technique used to identify functional groups in a molecule by measuring the absorption of infrared light at different wavenumbers. Each functional group absorbs IR radiation at characteristic frequencies, producing a spectrum with peaks that correspond to specific bond vibrations. The presence of peaks at certain wavenumbers can help deduce the functional groups present in the compound.
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Functional Group Identification
Identifying functional groups is crucial for determining the structure of an organic compound. By analyzing the IR spectrum, one can identify specific functional groups based on characteristic absorption peaks. For example, a broad peak around 3300 cm⁻¹ suggests an O-H bond, while a sharp peak near 1700 cm⁻¹ indicates a C=O bond, aiding in piecing together the compound's structure.
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