A, spectrum 4: ethoxy CH at about is a NMR triplet, and OCH at about is a NMR quartet. The two alkene methyls at about and each integrate to three protons; they are apparent NMR singlets on the overview but have small allylic NMR doublet splitting. The vinyl CH at about is correspondingly a narrow NMR multiplet, formally a quartet of quartets when its two methyl couplings are unequal, or approximately a NMR septet if they coincide. A broadened overview must not be used to declare all those small couplings exactly zero.
C, spectrum 5: the acetal CH at about and terminal C≡CH at about each integrate to one proton and show their small mutual long-range NMR doublet splitting. The ethoxy methyls give a six-proton NMR triplet near . The OCH region has two sets near and , each integrating to two protons. These are an ABX3 spin system: geminal coupling and coupling to CH produce approximately one doublet of quartets for each proton type, with second-order distortion in the expanded trace. Treating the whole region as one ideal four-proton NMR quartet misses the printed structure.
B, spectrum 6: the internal alkene CH near is a doublet of doublets of triplets from trans/cis coupling to CH and vicinal coupling to OCH. The two terminal alkene protons near – are distinct doublet of doublets-type signals, with possible additional small allylic splitting. OCH near is principally a NMR doublet. The acyl-alpha CH near is a NMR triplet, the middle CH near an approximate NMR sextet or overlapping NMR triplet of quartets, and the terminal methyl near a NMR triplet.
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