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RESEARCH PRODUCT

Structure and properties of N-methyl-N-(4-pyridyl)-nitramine and 1,4-dihydro-1-methyl-4-nitriminopyridine

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Abstract The molecular structure and spectral properties of N -methyl- N -(4-pyridyl)-nitramine ( 1 ) and 1,4-dihydro-1-methyl-4-nitriminopyridine ( 3 ) were investigated by the X-ray diffraction, FTIR, nuclear magnetic resonance (NMR) methods and DFT theoretical calculations. N -methyl- N -(4-pyridyl)-nitramine ( 1 ) crystallises in the orthorhombic Pbca space group. It is composed of two planar fragments; nitramino (N 2 O 2 ) group and the pirydyl ring. These two groups are twisted at about 70° with respect to each other, along the Ar–N bond. On the contrary, in compound 3 , they are coplanar to each other. Twist of the nitramino group in 1 with respect to the pirydyl ring leads to a significant increase in C–N bond length ca. 0.07 A in comparison to the analogous bond in the nitrimine 3 . The true nitramines, like 1 , give strong bands in the infrared spectra, in the regions 1252–1276 and 1488–1563 cm −1 . In the spectra of nitrimine 3 , the frequencies characteristic of the N -nitro group, appear at 1245–1255 and 1420–1450 cm −1 . The proton and carbon NMR spectra of 3 indicate that the ortho positions of the ring, in the liquid state, are magnetically equivalent, due to the fast rotation along the C N bond, which was formally a double bond. The nitramine 1 rearranges to 4-( N -methylamino)-3-nitropyridine, in 95% sulphuric acid, whereas the nitrimine 3 cannot rearrange in any way. The difference in the susceptibility towards rearrangement was explained by the electron deficient character of the migration terminus, i.e. the pyridine ring ( 3a ).