Jordan A. Tsenov

Infrared spectra and structure of phenylacetonitrile and of its carbanion: an ab initio force field treatment

Abstract The structures of phenylacetonitrile and of its carbanion have been studied on the basis of IR spectroscopic data (including literature results) and of ab initio force field calculations. The assignment (D. Croisat et al., J. Org. Chem., 157 (1992) 6435) of the IR bands of phenylacetonitrile, its d 5 analogue, and their carbanions has been confirmed. An excellent linear correlation ( R = 0.999) has been found between the theoretical and experimental IR frequencies of the species studied. The calculations predict well the strong increase in intensity (five to 42 fold) of the v CN , v S8 and v I9 bands which accompanies the conversion of the phenylacetonitrile molecule to its carbanion. The structures of both sodium and potassium derivatives of phenylacetonitrile in dimethyl sulfoxide are close to that of the kinetically free phenylacetonitrile carbanion. The carbanionic center is practically planar; the cyano group carries a considerable negative charge, but its influence on the carbanionic center is mainly inductive. The carbanionic charge is delocalized over the phenyl ring (0.42 e − ), methide (0.30 e − ), and cyano (0.28 e − ) groups.

Infrared spectra and structure of alkane- and cycloalkanecarbonitriles and of their carbanions: An ab initio force field treatment

Abstract The structure of alkane- and cycloalkanecarbonitriles (seven compounds) and of their carbanions has been studied by both infrared spectrometry and ab initio force field calculations. The carbanions (counter ions Li + , Na + and K + ) have been found to exist mainly as ionic aggregates in hexamethylphosphoric triamide solutions. The calculations describe well the marked decrease, by 124–214 cm −1 , in the nitrile band frequencies and also the strong increase, by 1–2 orders, in the nitrile band integrated intensities which accompany the conversion of the parent neutral molecules into carbanions. Cyclopropanecarbonitrile is remarkable as having the highest nitrile band intensity among all the neutral molecules and the lowest one among all the carbanions studied. This result has also been predicted by the calculations, and it can be explained by certain peculiarities in the structure of the particles. The conjugation of the carbanionic charge with the cyano group in the cyclopropanecarbonitrile carbanion is greatly hindered by the considerable deviation (estimated at 56°) of the cyano group from the ring plane. The carbanionic charges of the carbanions studied are delocalized over the cyano groups (0.30–0.41 e − ), carbanionic centres (0.08–0.29 e − ) and hydrocarbon moieties (0.34–0.63 e − ).

Infrared spectra and structure of products formed by electron transfer onsome substituted acrylonitriles

Abstract The structures of the products of electron transfer or substituted acrylonitriles have been studied by simultaneously taking into account infrared and quantum-chemical data. Conversion of neutral compounds into anion-radicals, monomeric dianions and dimeric dianions has been followed by infrared spectra.

Structural Effects on Nitrile Infrared Integrated Intensities of Alpha,Beta-Diaryl Cyanoethylenes: Hammett and Quantum Chemical Approaches

Abstract The nitrile infrared intensities of a series of a,β-diaryl cyanoethylenes were juxtaposed to the associated substituent constants, HMO and SCF-MO indices and fair to excellent correlations were established. The competitive resonance of the nitrile group with alpha-and beta-aryl substituents is discussed. HMO calculations were used to estimate the steric hindrance to conjugation caused by polycyclic substituents and SCF-MO calculations were made to obtain uniform predictions of nitrile intensities and frequencies for hetero-cyclic derivatives of acrylonitrile.