Ch3 12ch2 12ch2 oh

The 13C signal will be split into a quartet by the three methyl protons (JCH = 125 Hz) and each line of this quartet will be split into a triplet by the two protons on the adjacent carbon (2JCH = 4-6 Hz). Each of these 12 lines will be further split into a triplet by the two protons on the CH2OH group (3 JCH ~ 5 Hz). Thus our 13C chemical shift position will give as many as 36 lines in the spectrum, spreading our already miserable signal-to-noise ratio into a multitude of tiny peaks barely discernible in the noise. A similar cascade of splittings will complicate the other two resonances of n-propanol.

Later we will see how these couplings can be exploited in experiments that enhance the sensitivity of13 C spectra (INEPT), measure the number of hydrogens attached to each carbon (APT and DEPT), and correlate 13 C chemical shifts with 1H chemical shifts using a second dimension (2D-HETCOR, -HMQC, -HSQC, and -HMBC). But for detecting a simple 13 C spectrum, we need a way to suppress these 13C-1H couplings so we can observe a single line (singlet) for each 13 C resonance.

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