Ts. Kolev

Vibrational assignment of benzophenone and some of its isotopic species in the solid phase

Abstract Vibrational spectra of benzophenone- d 03 - d 5 - d 10 and - 18 O in the solid phase have been measured in the Raman (4000–20 cm −1 ) and infrared (4000–100 cm −1 . Their differential infrared linear dichroin spectra of oriented polycrystalline layers (4000– 400 cm −1 ) have been also recorded and studied. The assignment of the vibrational bands is performed using the group vibrational concept, isotopic shifts and polarization features of the normal modes. The presence of syn and anti -phase vibrations of both phenyl rings is rediscussed. The previous assignments of the in-plane deformation of the carbonyl group and of the fundamentals below 300 cm −1 are questioned and corrected.

Some molybdenum-containing chelating ion-exchange resins (polyampholites) as catalysts for the epoxidation of alkenes by organic hydroperoxides

Abstract Heterogeneous molybdenum-containing polymeric catalysts for the epoxidation of alkenes by organic hydroperoxides were prepared by a simple treatment of the chelating ion exchange resins (polyampholites) Amberlite IRC718, Amberlite IRC748 and Duolite C467 (Rohm&Haas, USA) with both the aqueous solution of sodium molybdate at pH 3.5 and solution of molydenyl acetylacetonate in toluene. The formation of the catalytically active centres by the interaction of the oxomolybdenum species from the reaction solution with ligand functional groups of the ion exchangers was proved. The stability of these polymeric complexes on multiple use with the epoxidation of cyclohexene by tert -butylhydroperoxide (TBHP) in the absence of an inert solvent at temperature 79°C and initial TBHP concentration of 1.2–1.3 mol l −1 was studied.

Crystalline Complexes Involving Amino Acids. I. l-Argininium Hydrogen Squarate

The title compound, C 6 H 15 N 4 O 2 + .C 4 H O - 4 , crystallizes in the triclinic space group P1 with two independent formula units in the unit cell. The arginine molecules are protonated zwitterions with the amino and guanidyl moieties each accepting a proton from the acid group and the squaric acid. The torsion angles along the central N-C-(CH 2 ) 3 -N chains are -166.8(2), 165.7(2), 168.9(2), 178.2(2)° in molecule I and -170.0(1), 148.9(2), 164.1(2), 163.7(2)° in molecule II, respectively. The C-C bond lengths within the squarate anions are consistent with a delocalized double bond around the hydroxyl-bearing C atom, 1.426(3) and 1.433(3) A versus 1.496(3) and 1.491(3) A for the adjacent and opposite bonds, respectively. The crystal structure consists of alternate layers of squarate and argininium moieties stacked along the c axis. The adjacent layers are connected to each other through specific ion-pair interactions (salt bridges) between the guanidyl group of the argininium and the squarate moieties.

Infrared Spectra of the Anion-Radicals of Benzophenone and Some of Its Isotopic Isomers

Abstract Band assignment of the infrared spectra of the anion-radicals of benzophenone-dO, -d10 and 18O has been given on the basis of isotopic shifts. The frequency of the νC=O band decreases by ca. 270 cm−1 with the transformation of neutral keton into anion-radical, due to the strong electron-withdrawing character of the carbonyl group; frequencies of the other modes decrease slightly, down to 30 cm−1.

Infrared Spectra and Structure of the Anion-Radicals of Substituted Benzophenones

Abstract Γ bands of 23 anion-radicals of meta- and para-substituted benzophenones have been assigned and compared to Γ C=O of the parent neutral compounds. Carbonyl frequencies of the anion-radicals (assigned on the basis of data for isotope-labelling compounds) have been found to appear in a 7–8 times wider frequency interval as compared to the frequency range of corresponding neutral compounds, i. e. the structural effects on Γ on the anion-radicals are 7–8 times stronger, compared to those on Γ C=O of the neutral benzophenones. Comparison of ketyl Γ with the sum of the substituent constants has shown three separate correlations for: i) ketyls free of nitro groups; ii) ketyls with nitro groups in para-position; iii) ketyls with nitro groups in meta-position. The absence of general correlation has been explaned by the different types of the odd-electron distribution. These results do reject a series of literature conclusions about the substituent effects on Γ of the anionradicals of substituted benzophen...

Vibrational assignment of benzil and its 18O substituted derivative

Abstract Vibrational spectra of benzil and benzil-18O in the solid phase and in the melt as well as in solution have been measured in the Raman (4000–20 cm−1) and the infrared (4000–100 cm−1). Their differential infrared linear dichroic spectra of oriented polycrystalline layers (4000–200 cm−1) have been also recorded and studied. The assignment of the vibrational bands is performed using the group vibrational concept, isotopic shifts and polarization features of the normal modes. The presence of syn- and anti-phase vibrations of both phenyl rings is rediscussed. The previous assidnments of the in-plane and out-of-plane deformation of the carbonyl group and some fundamentals of bicarbonyl moiety are questioned and corrected.

LFER approach to the effects of neutral and anionic substituents on the νCO bands of ring_ substituted ethylbenzoates and acetophenones

Abstract Satisfactory correlations have been found between ν CO of ethylbenzoates and acetophenones (60 compounds, solvent DMSO) with σ + substituent constants. LFER approach has been checked to ν CO of ethylbenzoates and acetophenones with anionic substituents (17 compounds). σ + constants of anionic substituents, determined on the basis of nitrile infrared frequencies and intensities, have been found to be satisfactorily reliable in the series studied.

Effects of Neutral and Anionic Substituents on the Carbonyl Stretching Band of Substituted Benzophenones

Abstract Satisfactory correlations were found of the frequencies of the title band (νCO) with 6+ and other substituent constants. The correlations proved valid for benzophenones with both neutral and anionic substituents (more than 100 compounds). The integrated intensities of the νCO bands (A1/2 CO) did not correlate with any type of substituent constants; the decrease in ACO in the cases of benzophenones with strong electron-releasing substituents was ascribed to a resonance-induced intensity borrowing from νCO BY THE aromatic skeletal bands (8-type). This statement wa confirmed by IR data few deuterated benzophenones.

Vibrational Assignment of Di-2-Pyridyl Ketone and Its 18O Labelled Isomer

Abstract Vibrational spectra of di-2-pyridyl ketone and di-2-pyridyl ketone-18O have been recorded in the solid and molten state in the infrared (4000–100 cm−1) and the Raman (4000–50 cm−1). Polarized Raman spectra of the molten state have also been measured. The assignment of vibrational bands is performed using the group vibrational concept, isotipic shifts data and polarization features of the normal modes. The presence of symmetric and antisymmetric vibrations arising from the coupling of both pyridyl rings is found and discussed.

The Vibrational Spectra of 9-Fluorenone and Some of Its Isotopic Isomers

Abstract Vibrational spectra of 9-Fluorenone, 9-Fluorenone-18O and 9-Fluorenone-d8 have been recorded in the solid state and solutions in the infrared and (4000–100 cm−1) and in the Raman (4000–50 cm−1). Differential infrared linear dichroic spectra have also been measured. The assignment of the vibrational bands is performed using the group vibrational concept, isotopic shifts and polarization features of the normal modes.