How is the peak affected in #C^13 NMR# by the number of H's attached to the carbon?

Question

Elias Aguila · Accepted Answer

In a "normal" #""^13"C"# NMR spectrum, the number of #"H"# atoms attached to the carbon does not affect the peak.

That's because most #""^13"C"# NMR spectra are broadband decoupled .

The couplings are removed by applying a continuous second radio signal that excites all the protons and cancels out their couplings with the #"C"# atoms.

Thus, the spectrum of 2-bromobutane consists of four singlets.

However, there is a technique called off-resonance decoupling , in which only the protons bonded to a given carbon atom split its signal.

Thus, a #"CH"_3# group appears as a quartet, a #"CH"_2# group appears as a triplet, a #"CH"# group appears as a doublet, and a quaternary #"C"# appears as a singlet.

So, the off-resonance decoupled spectrum of 2-bromobutane consists of two quartets, a triplet, and a doublet.

Isabella Acosta · Answer

undefined The peak in a C^13 NMR spectrum is affected by the number of H's attached to the carbon in terms of its splitting pattern. The number of adjacent hydrogen atoms influences the splitting of the C^13 signal, resulting in multiplets with different intensities and patterns. Specifically, the presence of adjacent hydrogen atoms leads to splitting of the C^13 peak into a multiplet, whereas carbons without adjacent hydrogens typically appear as singlets.