Laser Raman and infra-red spectra of biomolecule: 5-aminouracil

摘要

Laser Raman (200–4000 cm−1) and IR (200–4000 cm−1) spectra of 5-aminouracil were recorded in the region 200–4000 cm−1. Assuming a planar geometry and C_s point group symmetry, it has been possible to assign all the 36 (25a′ + 11a″) normal modes of vibration for the first time. The two NH bonds of the NH₂ group appear to be equivalent as the NH₂ stretching frequencies satisfy the empirical relation proposed for the two equivalent NH bonds of the NH₂ group. The two NH₂ stretching frequencies are distinctly separated from the CH/NH ring stretching frequencies. A strong and sharp IR band at 3360 cm−1 could be identified as the anti-symmetric NH₂ mode whereas the band at 3290 cm−1 with smaller density could be identified as the symmetric NH₂ stretching mode. All other bands have also been assigned different fundamentals/overtones/combinations.