摘要：

Attempts to deprotonate nitrocyclopropane led to solutions which showed strong ESR. signals (Fig. 1)and from which 1-nitro- l′-nitroso-bicyclopropyl (3) and 1,1′-dinitro-bicyclopropyl (2) were isolated. The activation energy for rotation about the central C, C-bond of 2 is estimated to be about 12 kcal/mol (¹ H-NMR. spectra in Fig. 2). In contrast, the oven-chain analogue 2,3-dimethyl-2,3-dinitrobutane (1) shows a methyl singlet down to −70° C. Low-temperature X-ray analyses of 1, 2, 3, and also of 1,1′-dinitro-bicyclobutyl (4) show that all four molecules have gauche-conformations but reveal striking structural differences between the openchain and the cyclic derivatives (Fig. 4–6): the central C, C-bond is long in 1 (1.575 Å), short in 2 (1.479 Å); the C, N-bonds are long in 1 (1.549 Å), short in 2 (1.488 Å); the orientation of the nitro groups is bisected in 2 and perpendicular in 1. The crystal structure of the ni

展开