FTIR and Raman Spectra Compared with Ab Initio Calculated Frequency Modes for 5-Aminouracil

Abstract

Infrared (IR) and Raman spectra of 5-aminouracil were recorded in the region 200-4,000 cm −1 . Assuming under the C s point group that the distribution of the normal mode of vibrations between the two species are planar (a ) and non-planar (a ), given by 25a + 11a of which 30 modes (21a + 9a ) correspond to the uracil moiety and six modes (4a + 2a ) correspond to the NH 2 group, with a comparison of theoretically ab initio calculated frequencies, the results are in reasonably good agreement with the experimental IR and Raman spectra. Consistent assignments have been made for the internal modes of the NH 2 group, especially for the anti-symmetric NH 2 stretching and bending modes. The nonequivalence of the two NH bonds of the NH 2 group suggests a difference in the strength of the two hydrogen bonds on the pyrimidine ring. Symmetry and anti-symmetry NH stretching modes of the NH 2 group show the invalidity of the empirical relationship. These two NH 2 stretching frequencies are distinctly separated from the CH/NH ring stretching frequencies. A strong and sharp IR band that acts at 3,380 cm −1 could be identified as the anti-symmetric NH 2 mode whereas the band at 3,290 cm −1 smaller density could be identified as the symmetric NH 2 stretching mode.

Comparison between Infrared and Raman Spectroscopic Analysis of Maturing Rabbit Cortical Bone

“…In a few studies, similar parameters obtained with Fourier transform infrared (FT-IR) and Raman microspectroscopy have been compared with each other. [26][27][28] However, usually these studies have been conducted on selected biochemical molecules, e.g., tripeptides 26 and 5-aminouracil, 27 rather than on biological tissues with more complex molecular structure. Gourion-Arsiquaud et al 28 compared the IR and Raman spectroscopic parameters in baboon bone.…”

A DFT study of vibrational spectra of 5-chlorouracil with molecular structure, HOMO–LUMO, MEPs/ESPs and thermodynamic properties

“…Here, because of spectral congestions of ν (C=O), some ring motions and H bonding modes, all stretching modes in ring have been found in the range of 1800–700 cm −1 . But, ν (C=C) vibration has been reported in the 1800–1600 cm −1 as assigned in the works [ 15 – 23 ]. Here, in the present work, 6 modes for ring stretching have been calculated at 1668 as ν (C 4 =C 5 ), 1398, 1191, 1161 (Kekule), 970 and 776 cm −1 (ring breathing), and in order to the 1666, 1402, 1190, 1170, 960 and 775 cm −1 have been recorded in strong intensities for IR spectrum, consequently Raman bands at 1665, 1400, –, 1060, 930 and 776 cm −1 with the intensity of medium strong in observed results.…”

“…These stretching modes have been affected with interaction of the H bonding and other important shifting modes for the reason of annoying of Fermi resonance [ 16 – 18 ]. Here, ν (C 1 =O 10 ) and ν (C 3 =O 11 ) modes have been optimized at 1806 and 1776 cm −1 to respective modes, but the other mixing ring modes are given in the PEDs, and these have been recorded in the IR at 1792 and 1772 cm −1 with relating to Raman at 1810 and 1772 cm −1 of these modes and as the reported works [ 15 – 18 ]. In-plane, β (C 1 =O 10 ) and β (C 3 =O 11 ) bending modes have been optimized at 607 and 362 cm −1 and these have been recorded in IR at 610 and – cm −1 , but Raman bands at 630 and 380 cm −1 as reported in refs [ 12 – 18 ].…”

“…In Ring modes (twelve modes): As phenyl ring, a pyrimidine ring of 5-chlorouracil has been assigned with the 12 fundamental modes , namely the 6 stretching modes in ring, 3 modes in deformation ring in-plane and 3 modes in ring deformation out-of-plane. These modes for stretching are complicated combination of C=C, C–N and C–C bonds in pyrimidine [ 15 – 18 ]. Here, because of spectral congestions of ν (C=O), some ring motions and H bonding modes, all stretching modes in ring have been found in the range of 1800–700 cm −1 .…”

Mercury Adsorption on Thiol-Modified Porous Boron Nitride: A Combined Experimental and Theoretical Investigation

“…The existence of the B–OH/B–NH 2 group provides a certain basic site, which is beneficial to the electrostatic adsorption of positively charged ions under alkaline conditions. After Hg 2+ adsorption, the spectrum of pBN–SH–Hg changed significantly, and a fresh peak at 1537 cm –1 can be observed, which is the superposition of CO stretching and N–H shearing or symmetric deformation . It can be identified from the spectrum of pBN–SH–Pb that there was a minor peak shift at 1625 cm –1 , which may be due to the fact that the grated −N–CS group can be able to capture the divalent metal cations through chelation.…”