Identify pairs of coupled protons in the compound whose COSY spectrum is shown below. <IMAGE>
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Examine the COSY (Correlation Spectroscopy) spectrum provided. COSY is a 2D NMR technique that shows correlations between protons that are scalar (J) coupled. Look for cross-peaks, which indicate coupling between protons.
Identify the diagonal peaks in the COSY spectrum. These represent the chemical shifts of individual protons in the molecule. Each diagonal peak corresponds to a specific proton environment.
Locate the off-diagonal cross-peaks. These cross-peaks indicate coupling between two protons. For example, if a cross-peak appears at the intersection of two chemical shifts, it means the protons corresponding to those shifts are coupled.
Assign the chemical shifts of the diagonal peaks to specific protons in the compound. Use the molecular structure (if provided) and the chemical shift values to determine which protons correspond to each peak.
Match the cross-peaks to the coupled protons. For each cross-peak, identify the two protons that are coupled. These pairs of protons are the coupled protons in the compound. Ensure that the coupling is consistent with the molecular structure and the expected J-coupling patterns.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
COSY Spectroscopy
COSY (Correlation Spectroscopy) is a two-dimensional NMR technique that provides information about the coupling between protons in a molecule. It allows for the identification of which protons are coupled to each other by displaying cross-peaks in the spectrum, indicating interactions. This technique is particularly useful for elucidating the structure of organic compounds by revealing connectivity between protons.
Coupled protons are hydrogen atoms in a molecule that interact with each other through scalar coupling, leading to splitting patterns in NMR spectra. The degree of coupling can affect the chemical shifts and multiplicity of the signals observed. Understanding which protons are coupled helps in determining the molecular structure and the spatial arrangement of atoms.
Spin-spin coupling refers to the interaction between the magnetic spins of neighboring nuclei, which results in the splitting of NMR signals. This phenomenon is quantified by the coupling constant (J), which indicates the strength of the interaction. Recognizing the patterns of splitting allows chemists to deduce the number of neighboring protons and their arrangement in the molecule.