NMR Spectra of Glycidaldehyde

Abstract

The NMR spectra of glycidaldehyde were measured at 40 and 60 Mc/sec. [Complex chemical formula] These complicated spectra of four interacting protons were analyzed by two methods: the ABKY approximation and the iterated ABCD solution. The various mathematical techniques developed should prove useful in the analyses of other complicated spin resonance spectra. The following spin‐spin coupling constants, $J_{\mathrm{ij}}$ in cycles per second and chemical shifts, ${\delta }_i$ in parts per million (relative to tetramethylsilane) were found: $$\begin{array}{ccccccccccc}& J_{\mathrm{AB}}& J_{\mathrm{AC}}& J_{\mathrm{BC}}& J_{\mathrm{AD}}& J_{\mathrm{BD}}& J_{\mathrm{CD}}& {\delta }_A& {\delta }_B& {\delta }_C& {\delta }_D\\ \text{40\hspace{0.17em}}\mathrm{Mc}/\sec & \text{5.54}& \text{2.04}& \text{4.90}& \text{−0.03}& \text{−0.32}& \text{6.36}& \text{3.096}& \text{3.158}& \text{3.356}& \text{8.922}\\ \text{60\hspace{0.17em}}\mathrm{Mc}/\sec & \text{5.54}& \text{2.09}& \text{4.87}& \text{+0.03}& \text{−0.31}& \text{6.24}& \text{3.098}& \text{3.166}& \text{3.356}& \text{8.922}\end{array}$$ The first three coupling constants are very close in magnitude to those obtained in other epoxides (in most cases to within 0.5 cps). The magnitude of the coupling constant between the aldehyde proton (D) and the adjacent proton (C) indicates that the D proton of the aldehyde group is probably on a time average, mainly in a plane perpendicular to the epoxide ring. The proton (D) could be either cis or trans to proton (C), but from a consideration of internal rotation interactions, it is probably in the trans configuration. The $J_{\mathrm{AC}}$ and $J_{\mathrm{BC}}$ coupling constants are consistent with an ``eclipsed‐ethanelike'' model rather than with an ``ethylenelike'' one. The coupling constants across the molecule, $J_{\mathrm{AD}}$ and $J_{\mathrm{BD}},$ are an order of magnitude smaller than the other constants. This is in agreement with the approximate attenuation factor of 1/10 for spin‐spin coupling through a single bond.