Hydrogen-nitrogen, infrared absorption

Bohlmann et al. (118-121) observed that an infrared absorption band between 2700-2800 cm is characteristic of a piperidine derivative possessing at least two axial carbon-hydrogen bonds in antiperiplanar position to the free-electron pair on the nitrogen atom. The possibility of forming an enamine by dehydrogenation can be determined by this test. Compounds which do not fulfill this condition cannot usually be dehydrogenated (50, 122,123). Thus, for example, yohimbine can be dehydrogenated by mercuric acetate,whereas reserpine or pseudoyohimbine do not react (124). The quinolizidine (125) enamines (Scheme 4), l-azabicyclo(4,3,0)-nonane, l-azabicyclo(5,3,0)decane, l-azabicyclo(5,4,0)undecane, and l-azabicyclo(5,5,0)dodecane have been prepared in this manner (112,126). 

Thus the splitting is also much smaller for ND3 than for NH3. It is, furthermore, more correct to say that the pyramid of the hydrogen atoms with the nitrogen atom at the top is turned inside out than to speak of the motion of the nitrogen atom, the amplitude of which, in view of the larger mass, will only be very small. The splitting of the levels causes a doubling in the spectrum. While for the infrared absorption spectrum only the transitions from an antisymmetrical to a symmetrical level or vice versa are permissible, the lines in the Raman spectrum correspond to the transitions between levels of the same character. 

The association constant of pyridazine with ethanol was found to be 4.9 (from electronic absorption spectra) and 6.8 (infrared absorption spectra), and the corresponding values for the strength of the hydrogen bond are 4.2 and 4.6 kcal. The hydrogen-bonded form of P3n-idazine was considered to comprise one alcohol at one azine-nitrogen at small mole ratios of alcohol to azine and to involve the second nitrogen at high mole ratios (an additional shift in the electronic spectrum. The association constants (3.1-3.8) of pyridine, quinoline, and isoquinoline with methanol in carbon tetrachloride have been determined by infrared spectroscopy. 

PMR spectra cannot indicate the presence of amide hydrogen because of rapid exchange of the proton with deuterium oxide solvent. We have found that nitrogen-cobalt bonded complexes with infrared absorptions at 1575 cm. may be formed when N-bromo primary amides react with pentacyanocobaltate(II). Comparison with the spectrum of a complex formed from an N-bromo secondary amide, in which no acidic hydrogen would be present, should help resolve this problem. 

It has long been known that it is difficult to wash chromia gel free of ammonium nitrate when it is prepared by methods similar to ours (2, S). A sample of our gel was analyzed in duplicate by the Micro-Tech Laboratories, Skokie, Illinois and reported to contain carbon, 1.26, 1.45% nitrogen, 2.60, 2.68% hydrogen, 3.12, 3.23%. Distillation from a solution of sodium hydroxide liberated ammonia equivalent to 1.60% nitrogen. Distillation from 3% sulfuric acid liberated carbon dioxide equivalent to 0.28% carbon. The nature of the remaining carbon is unknown. Infrared absorption of the pellets described in Section XI,A exhibited a sharp line at 1384 cm i characteristic of both NO3 and COg. Analysis of catalysts deliberately doped with urea established that urea, if any, corresponded to less than 0.15% carbon and 0.35% nitrogen. 

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