Assign the ¹³C NMR Spectrum
A proton-decoupled ¹³C spectrum shows one line for each unique carbon environment. These spectra are reconstructed from published experimental assignments: click a signal, then click the carbon(s) responsible for it. Equivalent carbons produce a single line, so a signal may belong to more than one carbon. Some molecules carry grayed-out signals — crowded clusters, such as the aromatic CH region, that a chemist would not assign from chemical shift alone. Those are shown for honesty but not asked; assign the lettered signals only.
¹³C Spectrum Reconstructed from Experimental Data
Expansion
Common Questions
Why is there no integration in ¹³C NMR?
Routine ¹³C spectra are not quantitative. Carbons relax slowly and unevenly, and the proton decoupling used to sharpen the lines also distorts their intensities, so peak height does not reliably count carbons. Assign by chemical shift, not by size.
Why are some signals grayed out?
Because assigning them individually is not a realistic ask. When several carbons of the same type crowd into a narrow window — six aromatic CH lines between 125 and 130 ppm, say — no organic chemist assigns each line from chemical shift alone; that calls for 2D experiments like HSQC. We gray those signals out, label the cluster for what it is, and ask you to assign only the signals you can genuinely place.
Where did the spectrum come from, and why is there no solvent peak?
Each spectrum is reconstructed from published experimental assignments in the nmrshiftdb2 database: the line positions are measured shifts from real compounds, redrawn cleanly. Because we rebuild the plot from the assigned shifts rather than reproduce a raw spectrometer file, there is no CDCl₃ solvent peak at 77 ppm — every line you see belongs to the molecule.
What is DEPT?
DEPT is an experiment that sorts carbons by the number of attached protons: CH and CH₃ point up, CH₂ points down, and quaternary carbons vanish. It is powerful enough to deserve its own page: in DEPT practice you read a ¹³C spectrum alongside DEPT-90 and DEPT-135 and classify every carbon.
Reconstructed from published data: assigned shifts from nmrshiftdb2 (CC BY-SA 4.0).