Assign each signal in the ¹³C NMR spectra to the molecule shown. (b)

Verified step by step guidance

1. Identify the molecular structure of the given compound and determine the number of unique carbon environments present.
2. Consider the symmetry of the molecule, which can help in identifying equivalent carbon atoms that will give rise to the same NMR signal.
3. Analyze the chemical shifts in the ¹³C NMR spectrum, which are influenced by the electronic environment around each carbon atom. Consider factors such as electronegativity of nearby atoms and hybridization.
4. Assign each unique carbon environment to a specific signal in the ¹³C NMR spectrum based on the expected chemical shift values. Use reference tables if necessary to match chemical shifts with typical values for different carbon types (e.g., alkane, alkene, aromatic, carbonyl).
5. Verify your assignments by considering the integration of the signals, if available, and ensure that the number of signals matches the number of unique carbon environments in the molecule.

Key Concepts

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 environment surrounding these nuclei in a molecule. The resulting spectra display signals that correspond to different carbon environments, allowing chemists to deduce structural features.

Chemical Shift

Chemical shift refers to the variation in resonance frequency of a nucleus due to its electronic environment. In ¹³C NMR, this is measured in parts per million (ppm) and indicates the type of carbon environment present in the molecule. Different functional groups and hybridization states affect the chemical shift, helping to identify the specific carbon atoms in the structure.

Integration and Multiplicity

In NMR spectroscopy, integration refers to the area under a signal, which correlates with the number of equivalent nuclei contributing to that signal. Multiplicity describes the splitting pattern of a signal, which arises from neighboring hydrogen atoms (in ¹H NMR) or other factors in ¹³C NMR. Understanding these concepts is crucial for interpreting the spectra and assigning signals to specific carbon atoms in a molecule.