Absorption spectra of 2-alkylnitramino-substituted 4(or 6)-methyl-5-nitropyridines and 2-(N-alkyl-N-nitrosoamino)-substituted 4(or 6)-methyl-3(or 5)-nitropyridines

Abstract

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

Nitrogen NMR shieldings of 2‐amino‐5‐nitro‐6‐methylpyridines

“…In the present case, the latter seems to be responsible for the absence of the β-effect on the amino nitrogens in compounds ( 5) and ( 6), with respect to (2) and ( 4), since the substituted pyridine rings are likely to interact sterically with the corresponding iso-propyl and tert-butyl substituents of the amino groups. The phenylamino substituent in compound (7) shows a significant deshielding of its nitrogen nucleus with respect to the corresponding alkylamino substituents in (1)(2)(3)(4)(5), and this is also typical of arylamines [2], as a result of π-electron delocalization which includes the lone-pair electrons of the amino nitrogen atom; the same applies to the nitrogen shieldings of the amino moieties in the nitramino and nitrosoamino structures (10-12).…”

“…Compound (10) was obtained as in Ref. [4]; the synthesis of compounds (11, 12) was a modification of that in Ref. [5], with temperature lowered to −10 • C and HNO 3 (d = 1.4) as a nitrating agent.…”