Why was #C^13NMR# spectroscopy developed after #H^1NMR# spectroscopy?

Question

Carter Allen · Accepted Answer

#""^13"C"# NMR spectroscopy was developed after #""^1"H"# spectroscopy because the technology was not yet available.

99.99 % of the H atoms in a compound are #""^1"H"#. Even so, the NMR signals are so weak that we need sensitive radio receivers to pick them up.

The weak signals' propensity to be obscured by noise is another issue.

Only about 1.1 % of the carbon atoms in a sample are #""^13"C"#. And the magnetic signal from a #""^13"C"# nucleus is only ¼ that of a proton. That makes it about 10 000 times more difficult to detect #""^13"C"# signals.

#""^13"C"# spectroscopy had to await the development of Fourier transform NMR spectroscopy, which could separate the signals from the noise.

Digitizing the signal was still a challenge, and the computations required large, expensive computers.

Prior to the commercial availability of "small" computers, NMR spectroscopy was not widely used.

And with that, NMR in organic chemistry began to blossom.

Brooklyn Barber · Answer

undefined C-13 NMR spectroscopy was developed after H-1 NMR spectroscopy because carbon-13 nuclei have a lower natural abundance and a lower sensitivity to NMR detection compared to hydrogen-1 nuclei, making it more challenging to develop the technology for carbon-13 NMR spectroscopy.