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Electronic spectra of nine title compounds were measured and the substituent effect on Xma x and ema x has been discussed. Competitive electron withdrawing by both the nitro groups in a molecule and a disturbance of mutual electronic interaction of substituent by a steric ortho effect were found. The preparation of five new 2- (N-aucyl-N-nitr•s•amin•)-4-and6-methyl-5-nitr•-and2-(N-methyl-N-nitrIn previous papers we described the UV spectra of 2-alkylamino-3(or 5)-nitro-4(or 6)-methylpyridines [1, 2]. In continuation of the investigations on this class of compounds we have determined and interpreted the UV spectra of 2-alkylnitramino-and 2-N-nitrosoalkylaminoderivafives in order to examine the substituent conjugation effects.It is known that the nitro group in the pyridine ring gives antifungal properties to the compounds [3]. The compounds studied (1-9) are of interest for the study of the interaction of the nitro group with other substituents in a molecule. EXPERIMENTALThe 2-(N-alkylnitramino)-4-methyl-5-nitropyridines (1, 2) and 2-(N-alkylnitramino)-6-methyl-5-nitropyridines (3, 4) were prepared as described previously [4, 5].2-(N-alkyl-N-nitroso~mino)-4-methyl-5-nitropyridines (5, 6), 2-(N-alkyl-N-nitrosoamino)-6-methyl-5-nitropyridines (7, 8), and 2-(N-methyl-N-nitrosoamino)-6-methyl-3-nitropyridine (9). To 20 ml of 14% HC1 2 g of compound 5--9 were added. After cooling the mixture below -10~ 10 ml of saturated NaNO 2 aqueous solution was added. The reaction

X-ray diffraction (XRD) studies have shown that 2-piperidyl-5-nitro-6-methylpyridine, C 11 H 15 N 3 O 2 , undergoes a structural phase transition at T = 240 K. The room temperature structure is tetragonal, space group I4 1 /a, with the unit-cell dimensions a = 13.993(2) and c = 23.585(5) Å. The pyridine ring takes trans conformation with respect to the piperidine unit. While pyridine is well ordered, the piperidine moiety shows apparent disorder resulting from a libration about the linking N-C bond. The low-temperature phase is monoclinic, space group I2/a. Contraction of the unit-cell volume by 2.3% at 170 K enables the C-H· · ·O linkage between the molecules of the neighbouring stacks. As result, the asymmetric unit becomes bi-molecular. The thermal librations of the piperidine and methyl groups become considerably reduced at 170 K and nearly fully reduced at about 100 K. The IR spectra and polarised Raman spectra agree with the X-ray structure and confirm the disorder effect on the piperidine ring. The assignment of the bands observed was made on the basis of DFT chemical quantum calculations. Copyright

Dipole moments of 2-N-methylamino-5-nitro-6-methylpyridine (I) and 2-N-methylamino-3-nitro-6-methylpyridine (II) were determined in solvents of different polarity and basicity. The solvent effect is discussed in terms of the twoparameter (*-␤) Kamlet-Taft expression. The solvent dependences of the energy of intramolecular charge-transfer transition and the frequency of the (NH) stretching vibration are in keeping with the dielectric results. It was found that the solvent-induced disturbance in the electronic structure of I is brought about by hydrogen bond interaction with the NH group. The strong intramolecular hydrogen bond in II is stable in weakly basic solvents and the electronic structure is insensitive to the environment. However, in more basic solvents the intramolecular hydrogen bond is partly broken and an N-H· · ·solvent hydrogen bond is formed, bringing about distinct changes in polarity and spectroscopic properties.

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