NMR-SPECTRA OF ORGANOGERMANIUM COMPOUNDS .10. SYNTHESES, C-13 AND GE-73 NMR-SPECTRA AND MOLECULAR MECHANICS CALCULATIONS OF GERMACYCLOPENTANES AND GERMACYCLOPENTENES

Germacyclopentane, its 1-methyl, and 1,1-dimethyl derivatives together with some germacyclopentenes were prepared and their C-13 and Ge-73 NMR spectra were determined. Molecular mechanics calculations of germacyclopentanes indicate that the symmetric twist form is the most stable in contrast to cyclopentane where the envelop and twist forms have much the same energy. Though both C-13 and Ge-73 chemical shifts are less sensitive to the stereochemistry of the methyl group as compared with the corresponding germacyclohexanes, the spectroscopic results can be explained in terms of the structures as depicted by molecular mechanics calculations.