NHVibrationen

NHVibrationen, short for N–H vibrations, is a term used in vibrational spectroscopy to describe the vibrational modes associated with nitrogen–hydrogen bonds in molecules. These vibrations are investigated to gain information about molecular structure, bonding environments, and interactions such as hydrogen bonding. The study of NH vibrations is important across organic chemistry, biochemistry, and materials science.

The most common NH vibration is the N–H stretching mode, which typically appears in the infrared spectrum around 3200–3500 cm^-1. Primary amines often show two N–H stretches, while secondary amines exhibit a single band. Amide and amine N–H stretches are sensitive to hydrogen bonding: stronger hydrogen bonding generally lowers the frequency and broadens the band. In addition, N–H bending or scissoring modes occur roughly in the 1560–1650 cm^-1 region and contribute to the overall vibrational fingerprint of a molecule. In proteins, NH vibrations contribute to characteristic bands such as the amide A band near 3300 cm^-1, and interact with the broader amide I and II bands used to assess secondary structure.

Factors influencing NH vibrations include the chemical environment, solvent, and molecular conformation. Isotopic substitution, such as replacing H with D (N–D), shifts vibrations to lower frequencies (roughly by a factor of about 1/√2), providing a diagnostic tool for spectral assignment.

Measurement is typically performed with infrared spectroscopy and, to a lesser extent, Raman spectroscopy. NHVibrationen are applied in functional group identification, conformational analysis, protein structure studies, and the characterization of polymers and pharmaceutical compounds. See also: N–H stretch, hydrogen bonding, vibrational spectroscopy, amide bands.