Draw the ¹³C NMR spectrum you would expect to see for each of the molecules shown.
(c)

Verified step by step guidance

1. Identify the unique carbon environments in the molecule. Each unique carbon environment will correspond to a distinct signal in the ¹³C NMR spectrum.
2. Consider the symmetry of the molecule. Symmetrical molecules may have fewer unique carbon environments due to equivalent positions.
3. Analyze the chemical shifts for each carbon. Carbons bonded to electronegative atoms or within functional groups will have characteristic chemical shifts.
4. Determine the splitting pattern, if any. In ¹³C NMR, splitting is less common due to the low natural abundance of ¹³C, but coupling with nearby protons can occur.
5. Sketch the spectrum, placing each signal at the appropriate chemical shift on the x-axis, and indicate the relative intensity of each signal based on the number of equivalent carbons.

Key Concepts

13C NMR Spectroscopy

13C NMR spectroscopy is a technique used to determine the structure of organic compounds by analyzing the magnetic environment of carbon atoms. Each unique carbon environment in a molecule produces a distinct signal in the spectrum, allowing chemists to infer the number and types of carbon atoms present. The chemical shift, measured in parts per million (ppm), provides information about the electronic environment surrounding each carbon.

Chemical Shift

Chemical shift in NMR spectroscopy refers to the resonant frequency of a nucleus relative to a standard in a magnetic field. In 13C NMR, the chemical shift indicates the electronic environment of carbon atoms, influenced by factors such as electronegativity of neighboring atoms and hybridization. Typical chemical shift ranges for carbon atoms vary, with sp3 hybridized carbons appearing upfield (0-50 ppm) and sp2 hybridized carbons downfield (100-150 ppm).

Symmetry and Equivalent Carbons

In 13C NMR, symmetry in a molecule can lead to equivalent carbon atoms, which produce a single signal in the spectrum. Identifying symmetry elements, such as planes or axes, helps determine which carbons are equivalent. Equivalent carbons experience the same electronic environment, simplifying the spectrum by reducing the number of distinct signals, which is crucial for interpreting complex molecules.