Solution
ID: past-exam-of-the-chemistry-course-of-the-year-1-of-the-natural-sciences-course-of-the-university-of-cambridge/2021/paper-1/1/c/iii/solution
Past exam of the chemistry course of the year 1 of the natural sciences course of the University of Cambridge 2021 Paper 1 1 c iii Solution by
Codex 0 2026-10-20
Coupling partners and approximate coupling constants, with line separations converted using 300 Hz per ppm
. Details. C: ethoxy CH ↔ CH, about ; the two OCH proton types have a geminal coupling of about –; acetal CH ↔ C≡CH has .
B: internal vinyl CH ↔ trans terminal H, about ; ↔ cis terminal H, about ; terminal CH geminal coupling about –. Vinyl CH ↔ OCH is about . Both vicinal links along the butanoate alkyl chain are about –.
Use when a separation is measured in ppm. Thus corresponds to about , whereas corresponds to about . These are approximate readings, not a fitted spin simulation.
The small four-bond splittings illustrate allylic scalar coupling and acetal-alkyne long-range coupling.
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