Deuterium oxide, infrared spectra

Primary amines may be readily distinguished from secondary and tertiary analogues by the presence of two absorption bands in the infrared spectrum between 3320 and 3500 cm-1 (symmetric and antisymmetric NH str.). Secondary amines exhibit a single absorption band at about 3350 cm-1 (NH str.). In both cases deformation modes for the NH bond appear at about 1600 cm-1. There is no satisfactory absorption to allow a definitive characterisation in the case of tertiary amines. In the nuclear magnetic resonance spectrum of primary and secondary amines, the nitrogen-bound hydrogens are recognisable by their replaceability on the addition of deuterium oxide. 

Fried and Wintersteiner - oxidized streptomycin trihydrochloride with bromine water to an amorphous, antibiotically inactive product The relatively strongly acidic nature of this substance, which they named streptomycinic acid, was demonstrated by electrometric titration. In the infrared spectral region the substance exhibited an absorption maximum at a wave length of 6.06m, which was partially displaced to 5.81m when the spectrum was observed in the presence of deuterium oxide and deuterium chloride. A shift of this type is usually found with dipolar ions and was taken therefore as an indication of the expected dipolar ion character of streptomycinic acid. 

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. 

The infrared spectrum of phosphatidylserine in deuterium oxide (D2O) was recorded and the deconvoived carbonyi region is shown beiow in Figure 7.3. What does this band suggest about the conformation of phosphatidyiserine ... 

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