FT-IR, FT-Raman, NMR and UV-vis spectra, vibrational assignments and DFT calculations of 4-butyl benzoic acid

Article · January 2012with336 Reads
DOI: 10.1016/j.saa.2011.09.058 · Source: PubMed
Abstract
The solid phase FTIR and FT-Raman spectra of 4-butyl benzoic acid (4-BBA) have been recorded in the regions 400-4000 and 50-4000cm(-1), respectively. The spectra were interpreted in terms of fundamentals modes, combination and overtone bands. The structure of the molecule was optimized and the structural characteristics were determined by density functional theory (DFT) using B3LYP method with 6-311++G(d,p) as basis set. The vibrational frequencies were calculated for monomer and dimer by DFT method and were compared with the experimental frequencies, which yield good agreement between observed and calculated frequencies. The infrared and Raman spectra were also predicted from the calculated intensities. (13)C and (1)H NMR spectra were recorded and (13)C and (1)H nuclear magnetic resonance chemical shifts of the molecule were calculated using the gauge independent atomic orbital (GIAO) method. UV-visible spectrum of the compound was recorded in the region 200-400nm and the electronic properties HOMO and LUMO energies were measured by time-dependent TD-DFT approach. The geometric parameters, energies, harmonic vibrational frequencies, IR intensities, Raman intensities, chemical shifts and absorption wavelengths were compared with the available experimental data of the molecule.
  • ...The exact position of these bands depend upon the nature of the substituent to the phthalocyanine ring and the type of central metal ion, which is also supported from the TD-DFT calculations with B3LYP/6-311G++(d,p), CC-PVTZ, LANL2DZ method for the TSNiPc molecule in DMSO solvent as well as in gas phase. Karabacak et al [18] reported that electronic absorption spectra obtained by TD-DFT calculations with B3LYP/6-311G++(d,p) method are compatible with the experimental results. The energy gap of HOMO-LUMO energy levels (Table.1) ...
  • ...In the last years, considerable efforts have been devoted to theoretically and experimentally study of the benzoic acid derivatives [1‒14]. Thus, a number of these compounds were investigated: p‒hydroxybenzoic, m‒anisic, vanillic, and syringic acids [1]; 4‒butyl benzoic acid [2]; methyl‒ and methoxybenzoic acids [3]; m‒trifluoromethylbenzoic acid [4]; 4‒(2,5‒di‒2‒thienyl‒1H‒pyrrol‒1‒yl)benzoic acid [5]; p‒(p‒hydroxyphenoxy)benzoic acid [6]; toluic acid [7]; 2‒(4‒hydroxyphenylazo)benzoic acid [8]; 2‒amino‒5‒bromo‒benzoic acid methyl ester [9]; 4‒(trimethylammonium)benzoic acid chloride [10]; 2,3,4‒tri‒fluoro‒benzoic acid dimer [11]; 2‒[[14]. All of the above mentioned molecules were mainly modeled by density functional theory (DFT), and the simulation outcomes were compared with the available experimental results (e.g. ...
  • ... CH stretching vibrations in methyl groups have been formed at lower frequencies in comparison with aromatic CH ones. These results are also reported for compounds containing different methyl aromatic rings.[24] The frequency of symmetric CH stretching mode on methyl is computed as lower than asymmetric modes for the tolbutamide structure. Symmetric and antisymmetric CH stretching vibrations for methyl on aromatic rings have been reported at ∼ 2870 and ∼ 2980 cm −1 , respectively.[36,37] For tolazamide, the peaks at 2980 and 2958 cm −1 in FT-IR ...
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