Consider the following molecule and data:


$$ \begin{align} \mathrm{H_a} &= \pu{1.0 ppm} &\quad J_\mathrm{ab} &= \pu{5.0 Hz}\\ \mathrm{H_b} &= \pu{3.0 ppm} &\quad J_\mathrm{bc} &= \pu{8.0 Hz}\\ \mathrm{H_c} &= \pu{6.0 ppm} &\quad J_\mathrm{ac} &= \pu{1.0 Hz}\\ \end{align} $$

Draw a splitting diagram for $\mathrm{H_b}.$ $(\pu{1 box} = \pu{1 Hz})$

Tried to draw the splitting diagram and ended up with this diagram:

My splitting diagram

I am also stuck as to how to draw the spectrum of the whole molecule as I feel $\mathrm{H_a}$ would be triplet of triplet. Am I on the right track and how to draw the sketch of the spectrum?

  • 1
    $\begingroup$ You missed a split. The central peak must also split on the last coupling. $\endgroup$ – Jan Oct 15 '19 at 8:28

According to given data, you may consider expected peak patterns are not complicated such as $\mathrm{ABX}$ or $\mathrm{A_2B}$ patterns (more reading look here. This is simply a $\mathrm{A_2X}$ pattern ($\delta_X = \pu{6 ppm}$ and $\delta_A = \pu{1 ppm}$ without geminal coupling of two $\ce{H_b}$ protons), and hence, peak is a $dt$ for $\ce{H_b}$ as depicted below with relative heights of the peaks:

Hb peak

Similarly, $\ce{H_c}$ is also a $dt$ resonance with $J = 1 \text{ & } \pu{8 Hz}$ and $\ce{H_a}$ is a $tt$ with $J = 1 \text{ & } \pu{5 Hz}$. OP should able to figure out the intensities of relevant peaks.

A valuable reference:

Roy H. Bible, Jr., Ph.D., In Interpretation of NMR Spectra: An Empirical Approach; Springer Science: New York, NY, 1965 (https://doi.org/10.1007/978-1-4684-8288-1) (Note: Most relavent to this question is chapter 4 of the book titled "Higher-Order Spin Patterns and Multiple Resonance").


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