1980 Volume 53 Issue 8 Pages 2318-2321
The conformations of sodium enolate anions, derived from diethyl malonate and diethyl alkylmalonates (alkyl=methyl, ethyl, propyl, isopropyl, butyl, isobutyl, and s-butyl), have been determined to be Z,Z-type by the analysis of their 1H-NMR spectra in DMSO. In the case of diethyl t-butylmalonate, such a Z,Z type contributes to the lesser extent to the conformations of the sodium enolate anion because of repulsion between the t-butyl substituent and the two ethoxyl groups, which exist in three types (Z,Z, Z,E, E,E) of conformation, as is evident in the 1H-NMR spectra. The IR spectra of sodium diethyl malonate in DMSO showed two characteristic absorption bands at 1679 and 1556 cm−1. The IR isotope shifts upon the use of the enolates of diethyl malonate-2-13C and diethyl malonate-1,3-13C2 suggested that these two bands are attributable to the C··O and C··C··C bonds. All sodium diethyl alkylmalonates except for the t-butyl derivative have two characteristic IR bands in the region of 1500–1700 cm−1, the bands on the high-frequency side of which have nearly equal wave numbers, while those on the low-frequency side have a good correlation with the substituent constant, σ*.
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