Computational and experimental studies on the IR spectra and structure of the simplest nitriles (C₁ and C₂), their anions, and radicals

Abstract

ABSTRACT:The structure and infrared spectra of formonitrile (hydrogen cyanide) and acetonitrile, their anions, and radicals (45 species in all) have been studied by density functional theory (DFT) B3LYP 6-31ϩϩG(d,p) calculations. The results obtained have been compared with the literature and original experimental data. The zero-point vibrational energy (ZPVE)-corrected deprotonation energies of the studied (and other) nitriles correlate fairly well (R ϭ 0.94) with their pK a values, measured in dimethyl sulfoxide (DMSO). The theoretical cyano stretching frequencies C'N of the species studied have been found to correlate satisfactorily (R ϭ 0.97) with the experimental ones. The latter correlation can be used for a theoretical estimation of C'N of many nitriles, their anions, and radicals. The geometry parameters for the molecules, calculated by the same theoretical method, practically coincide with those determined experimentally in the gas state.

IR spectral and structural studies of 4‐aminobenzenesulfonamide (sulfanilamide)‐d0, ‐d4, and ‐15N, as well as their azanions: Combined DFT B3LYP/experimental approach

“…The absence of negative frequencies or negative eigenvalues of the second-derivative matrix confirmed that the stationary points correspond to global minima on the PEHS [16]. The use of 6-31ϩϩG(d,p) basis set in DFT computations has recently resulted in better or equally good spectral and structural predictions, compared with other basis sets for both organic molecules and anions [11,12,19,20]. No scaling in the density functional force field was done.…”

“…The charge change values ⌬q i ϭ q i (anion) Ϫ q i (molecule) are usually quite informative in showing the distribution of the new (e.g., carbanionic, azanionic) changes in anions (Refs. [10,11,13,14,19,20,28,29,34] and references therein). According to the present calculations, the new (azanionic) charge of 2a is distributed, as follows: 0.08e Ϫ , 0.23e Ϫ , and 0.12e Ϫ are delocalized over the amino, phenylene, and sulfonyl groups, respectively, and 0.57e Ϫ remain localized at the azanionic center (cf.…”

DFT and experimental study on the IR spectra and structure of 2-hydroxy-3-methoxybenzaldehyde (o-vanillin) and its oxyanion

“…The DMSO as polar aprotic solvent usually de- Table 2. The agreement between the experimental and calculated values is very good -the mean absolute deviation between observed and calculated frequencies is 16.5 cm À1 , which value is not away from the low border of the 15-25 cm À1 interval of deviations, typical for the DFT calculations for molecules containing carbonyl or cyano groups [19][20][21][22][23][24][25][26][27].…”

“…Table 1 Total energies (E), Gibbs free energies (G), zero-point vibrational energy (ZPVE) and relative energies (E rel ) of conformers of o-vanillin and its anion. acidities in polar aprotic solvents [19][20][21][22][23][24][25][26] (and references therein): low E D 's high acidities low pK a values.…”

Analysis of the nitrile and methyl torsional vibrations of n‐propyl cyanide in its S0 electronic state

“…, have been studied widely in nitrile compounds [25][26][27][28][29][30], experimental data about the lowest frequency torsional modes are scarce. For n-propyl cyanide, experimental data have not been reported for the m 30 and m 28 torsional modes.…”