Infrared Spectra and Normal Vibrations of N,N-Dimethylformamide and N,N-Dimethylthioformamide

Durgaprasad, Gummadi; Sathyanarayana, D. N.; Patel, C. C.

doi:10.1246/bcsj.44.316

Cited by 111 publications

(54 citation statements)

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“…C¼ ¼C (Ar) Stretch absorbance and the aromatic peak $1500 cm À1 was eliminated by over-subtraction. 45,46 Surprisingly, the addition of CuCl in IR Solution 2 did not produce the shifts documented by literature. The only observable change was a slight decrease in the frequency of the NAH bend by approximately $10 cm…”

Section: Ir Experimentsmentioning

confidence: 87%

A study of Cu(I)‐ethylene complexation for olefin–paraffin separation

Chen¹,

Eldridge²,

Rosen³

et al. 2011

AIChE Journal

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The current cryogenic distillation technology used for olefin–paraffin separation incurs extensive capital and operating costs. An alternative olefin–paraffin separation process, based on reactive absorption, could yield significant cost reductions. The research efforts described herein explored the structural characteristics of an NMP‐CuCl‐aniline absorption solution with ethylene to aid future development of olefin–paraffin separation systems. Solution IR and 1H NMR spectroscopy suggested weak and labile Cu(I)‐ethylene and Cu(I)‐aniline coordination, which point to the coexistence of multiple structures in solution. Experiments also revealed solvent‐dependent and temperature‐dependent coordination. The agreement of the collected spectral data with literature implied single ethylene coordination, whereas the Cl− ion likely remained coordinated with Cu(I). Solvent interference prohibited detailed investigation of IR spectra, but 1H NMR spectroscopy showed more promise as an analytical technique for the NMP‐CuCl‐aniline‐ethylene system. Finally, a tradeoff appears to exist between ethylene capacity and complex stability, and thus, an optimal ligand must be found that balances these two competing needs. © 2010 American Institute of Chemical Engineers AIChE J, 2011

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Section: Ir Experimentsmentioning

confidence: 87%

A study of Cu(I)‐ethylene complexation for olefin–paraffin separation

Chen¹,

Eldridge²,

Rosen³

et al. 2011

AIChE Journal

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“…The initial force field obtained from calculations using the GAMESS program was then recalculated from mdyn/A°, mdyn⋅A°/rad 2 , and mdyn/rad (for bond-bond, bond-angle, and angle-angle coupling force constants, respectively) into units of 10 6 cm -2 using the coefficients 1.5601, 1.4313, and 1.3131. Then, the force field was partially scaled.…”

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confidence: 99%

“…Nevertheless, several quantum-chemical ab initio and DFT calculations using various basis sets and approximations predicted C s point symmetry (planar skeleton) for isolated DMF [7,10] and monomeric fragments of its dimers [11,12]. The vibrational problem in terms of a valence-force field approximation [2,3,5,7] was also solved for a planar model of the DMF skeleton. An analogous situation occurred for the determination of the equilibrium configuration of the closest DMF analogs FA and MFA, for which planar and pyramidal skeletal structure models were also examined.…”

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confidence: 99%

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Modeling of structures and calculation of IR vibrational spectra of N,N-dimethylformamide dimers by density functional theory

et al. 2011

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UDC 539.19We present results of ab initio and DFT calculations of the structure and IR vibrational spectra of the monomer and dimers of N,N-dimethylformamide (DMF). The calculations were carried out in the B3LYP/cc-pVDZ approximation with subsequent force-field scaling. The calculated characteristics of the vibrational spectra of DMF show satisfactory agreement with experimental values, allowing them to be used in spectral and structural analysis.Introduction. Dimethylformamide (DMF) is one of the simplest amides and has several interesting properties. DMF does not contain an NH group, which is responsible for the nature of the intermolecular structure formed by this compound in the condensed state. The methyl and aldehyde groups act as proton donors in forming dimeric and polymeric structures of DMF. Therefore, in contrast with the closest analogs of DMF, formamide (FA) and methylformamide (MFA), the molecular clusters of DMF that are formed in the liquid phase have comparatively weak binding energies and vibrational spectra that are unperturbed by the effect of strong H-bonds. Thus, DMF is a convenient subject for studying the structural and spectral characteristics of molecular systems that are important from biological and technical viewpoints. Furthermore, liquid DMF is an important aprotic dipolar solvent. DMF often fulfills the role of an organic ligand in complexes with ions and compounds of various metals owing to the presence in it of the carbonyl.The molecular structure and vibrational spectra of DMF were studied several times both experimentally [1-9] and theoretically [7,8,[10][11][12]. However, the question of whether the molecular skeleton is planar or non-planar has not yet been answered. Also, the low symmetry of the molecule is responsible for significant interactions between vibrational modes. This causes definite difficulties in assigning vibrational bands and lines. Therefore, vibrational spectra of monomeric and dimeric forms of DMF have also not been conclusively interpreted.Herein results of quantum-chemical calculations of the structure and energy and spectral characteristics of DMF monomer and dimers are presented. Experimental IR absorption spectra are interpreted. Vibrational spectra of DMF are modeled in the gas and liquid phases.Experimental. IR absorption spectra of DMF were recorded in the range 400-4000 cm -1 on a Bruker Vertex 70 spectrophotometer. The first sample was prepared as a solution of DMF in CCl 4 (0.05 M). The second sample was pure DMF. IR spectra of the samples were recoded in a KBr cuvette (0.05 mm).Calculations. Structural and spectral characteristics of DMF monomer and dimers were calculated using the applied quantum-chemical program GAMESS [13,14]. The results were visualized using the MacMolPlt program [15]. The standard basis sets cc-pVDZ and cc-pVTZ [16], DFT methods, and the hybrid functional B3LYP [17][18][19] were utilized to optimize the equilibrium structure and calculate the force field and harmonic vibrational eigenfrequencies and intensities in IR spec...

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“…Normal coordinate analysis of the dimethyldithiocarbamate anion (12) and dimethylamides and thioamides (13) suggest that a high degree of coupling of i.r. modes takes place and hence few of the bands can be described as 'pure'.…”

Section: Infrared Spectramentioning

confidence: 99%