Pavol Hrnčiar

The photochemical behaviour of 3-(N,N-dimethylamino)-2H-1-benzopyran-2-one in tetrachloromethane: the influence of chloromethanes on quenching of fluorescence

Abstract 3-( N , N -dimethylamino)-2 H -benzopyran-2-one (DMAC) sensitizes the decomposition of CCl 4 during the photolysis in the near UV region (λ > 290 nm). The products of the photolysis are 3-( N -methylamino)-2 H -1-benzopyran-2-one (MAC) as a result of the demethylation of DMAC and the compounds formed by the reaction of DMAC with the trichloromethyl radical 3-( N , N -dimethylamino)-3,4-bis(trichloromethyl)-2 H -3,4-dihydrobenzopyran-2-one and hydrochloride DMAC. Recombination of ·CCl 3 radicals yields hexachloroethane. The ratio of the products depends on the reaction conditions (the concentration of DMAC, the light intensity and the temperature). The primary step in the mechanism of the sensitization of CCl 4 is assumed to be the formation of the excited state, charge transfer (CT) complex of the type DMAC δ+ …CCl 4 δ− . Chloromethanes CH x Cl 4− x ( x = 0,1,2) quench the fluorescence of DMAC and MAC. The Stern—Volmer constant for MAC is related to the electron affinity of chloromethanes.

Complexation of phthalides and substituted 3-benzylidene phthalides with Cr(CO)6

Abstract The acid-catalysed complexation of various substituted phthalides with Cr(CO)6 has been studied. Complexation of substituted 3-benzylidene phthalides takes place at the phenyl ring in most cases, but with di-halogeno-substituted 3-benzylidene phthalides the complexation took place at the phthalide moiety. An explanation of this difference is based on molecular modelling quantum chemical calculations.

Fermi Resonance in Substituted Z-3-Methylene Phthalides

SummaryThe absorption bands of the C=O Stretching vibrations of a series of thirty-nine substitutedZ-3-methylene phthalides (1a-s, 2a-h, 3a-f, 4a-c, and5a-c) were measured in CHCl3 and CCl4. The two-levelFermi resonance effect on the infrared spectra of the above compounds was investigated after deconvolution and band separation. The wave numbers of the unperturbed fundamental C=O stretching vibrations exhibit excellent linear correlations withHammets constants of substituents and13C NMR chemical shifts of the C=O group.ZusammenfassungDie Absorptionsbanden der C=O-Streckschwingung von 39 substituiertenZ-3-Methylenphthaliden (1a-s, 2a-h, 3a-f, 4a-c und5a-c) wurden in CHCl3 und CCl4 vermessen. Durch Dekonvolution und Bandentrennung konnte der EinflußFermi-Resonanz auf die Infrarotspektren der obengenannten Verbindungen untersucht werden. Die Wellenzahlen der ungestörten C=O-Streckschwingungen ergeben ausgezeichnete lineare Korrelationen mit denHammetschen Substituentenkonstanten und den13C-NMR-Verschiebungen der Carbonylgruppe.

Spectral properties and kinetics of the alkaline hydrolysis of chromium, tricarbonyl[3-[(η6-aryl)methylene]-Z-1(3H)-isobenzofuranones]

Abstract The infrared and 13 C NMR spectra and the kinetics of alkaline hydrolysis of chromium, tricarbonyl[3-[( η 6 -aryl)methylene]- Z -1(3H)-isobenzofuranones] have been studied in comparison with those of 3-arylmethylene- Z -1(3H)-isobenzofuranones. The 13 C NMR spectroscopy has been found to be the most suitable tool for recognition of the site of complexation in the 3-arylmethylene- Z -1(3H)-isobenzofuranone system. A statistically significant correlation has been found between the arithmetic means of the wave numbers of symmetric and asymmetric stretching vibrations of Cr(CO) 3 group and σ p constants of the substituents. The large slope of this linear dependence suggests an important role of the mesomeric mechanism in the transmission of electronic effects to the Cr(CO) 3 moiety. The strong electron-withdrawing effect of the Cr(CO) 3 group causes a significant decrease of the polarity of the phthalide CO bond. The reaction rates of the alkaline hydrolytic ring-opening reaction dramatically increase due to the effect of Cr(CO) 3 group. The absorption bands of the carbonyl stretching vibrations are markedly split due to Fermi resonance effect. After mathematical correction for Fermi resonance the wave numbers of the unperturbed fundamental CO stretching vibration and the log k values of alkaline hydrolysis exhibit significant linear correlations mutually, as well as with Hammett σ substituent constants. Chartons transmissive factors γ (PhCr(CO) 3 ) have been determined for tricarbonylchromiumphenyl system using the parameters of the linear correlations. The efficiency of the substituent effect transmission is high in CCl 4 , because a back-donation effect of the carbonyl ligands and decreases in CHCl 3 due to the hydrogen bonding between carbonyl groups and solvent molecules. The preparation of some novel chromium, tricarbonyl[3-[( η 6 -aryl)methylene]- Z -1(3H)- isobenzofuranones] is described.

Characterization of electronic properties of the Cr(CO)3 group in chromium, tricarbonyl [3-[(η6-aryl)methylene]-Z-1(3H)-isobenzofuranones] using spectral and theoretical methods

Abstract The IR, 13C- and 17O-NMR spectral characteristics of the Cr(CO)3 group in a series of eight chromium, tricarbonyl[3-[(η6-aryl)methylene]-Z-1(3H)-isobenzofuranones] were correlated mutually as well as with theoretical data obtained by optimized MMX force-field and EHT calculations. The net charges on the carbon and oxygen atoms of the CO group and their differences were found as the most appropriate quantitative characteristics for the electronic properties of the Cr(CO)3 group. Using the results of the previously reported linear correlations, the electron-withdrawing effect of the PhCr(CO)3 moiety, weakened by the back-donation effect, was estimated as σα≅0.45 on the scale of Hammett substituent constants.

Structure elucidation of acetylation products of 2-acyl-1,3-indanediones by correlation of infrared spectral data

Summary2-(1-Acetoxyalkylidene)- and 2-(1-acetoxybenzylidene)-1,3-indanediones (1a–1e) were proven to be the products of acetylation of 2-acyl-1,3-indanediones (2a–2e) by ketene using a detailed investigation and correlation analysis of infrared spectral data as well as1H-NMR and13C-NMR spectra. Study by means of CNDO/2 and MMPI methods also demonstrates that the structure1 is more stable as the alternative one of 2-acyl-3-acetoxy-2-indene-1-ones (5). It was shown that the recently proposed general correlations v(C=O)s vs. v(C=O)as and v(C=O) vs. ∑X+(R) as well as the mechanical anharmonicities of asymmetric C=O stretching vibration can be successfully used as a tool of structural diagnostics of cyclic 1,3-dicarbonyl compounds.Zusammenfassung2-(1-Acetoxyalkyliden)- und 2-(1-Acetoxybenzyliden)-1,3-indandione (1a–1e) wurden mittels einer detaillierten infrarot-spektroskopischen Untersuchung (IR-Korrelation) und1H-NMR und13C-NMR Spektroskopie als Acetylierungsprodukte von 2-Acyl-1,3-indandionen (2a–2e) mit Keten nachgewiesen. CNDO/2- und MMPI-Rechnungen zeigten auch, daß Struktur1 stabiler ist, als die der alternativen 2-Acyl-3-acetoxy-2-inden-1-one5. Es wird gezeigt, daß die kürzlich vorgeschlagenen allgemeinen Korrelationen v(C=O)s gengen v(C=O)as und v(C=O) gegen ∑X+(R) und auch die mechanischen Anharmonizitäten der asymmetrischen C=O Streckschwingung erfolgreich als Werkzeug zur Strukturaufklärung cyclischer 1,3-Dicarbonyl-Verbindungen eingesetzt werden können.

17O NMR chemical shifts of 3-(substituted methylene)-(Z)-1(3H)-isobenzofuranones: correlations with IR stretching wavenumbers and AM1 charges

17O NMR chemical shifts were determined for 1(3H)‐isobenzofuranone, its 3‐methylene‐ and 3‐(Z)‐(methylmethylene) derivatives and a series of 3‐aryl‐, 3‐aryloxy‐ and 3‐arylthiomethylene‐(Z)‐1(3H)‐isobenzofuranones. The observed δ(17O) values of the C=O‐group of the furanone moiety in the arylidene series show significant linear dependences on the wavenumber of the IR stretching vibration, ν(CO), the AM1 charge density at the double bond oxygen, q(O), and the Hammett σ+ constant of the substituent in the phenyl ring. These findings suggest that the substituent effects are efficiently transmitted from the phenyl ring to the C=O group via the conjugated double bond system of the 3‐arylidene‐(Z)‐1(3H)‐isobenzofuranone. In the case of aryloxy and arylthio derivatives these correlations were less significant than in arylidene compounds, reflecting the diverse effects of the heteroatoms (O or S) on the transmission mechanism.

Synthesis of 3-(N,N-dimethylamino)-2H-1-benzopyran-2-one

Abstract The reaction of salicylaldehyde, betaine and acetic anhydride gives 3-(N,N-dimethylamino)-2H-1-benzopyran-2-one in contrast with the published 2-(N,N-dimethylamino)-1,3-indandione.

Photochemical Z-E isomerization of benzylidenephthalides: influence of oxygen on the course of isomerization

Abstract Z isomers of benzylidenephthalides were photochemically isomerized to the corresponding E isomers. Direct photolysis leads to a low proportion (3% – 5%) of Z isomers in the reaction mixture in all cases. A significant influence of the substituents on the proportion of E isomers was observed in the benzophenone-sensitized reaction. The influence of azulene on the sensitized isomerization of unsubstituted and 3-(4-nitrobenzylidene)phthalide in both outgassed and oxygen-saturated solutions was also studied.

Preparation of 2-N-methylamino-1,3-indanedione by photochemical demethylation of 2-N,N-dimethylamino-1,3-indanedione

Abstract 2- N,N -dimethylamino-1,3-indanedione (DMAI) undergoes demethylation during photolysis (λ > 290 nm), producing 2- N -methylamino-1,3-indanedione (MAI) under conditions of direct or sensitized reaction. Ferrocene successfully quenches demethylation, while ethyl iodide accelerates the reaction rate. The yield and the rate of formation of MAI strongly depend on the reaction conditions, mainly on the solvent, the concentration of DMAI and the presence of an electron acceptor (substituted nitrobenzene). The UV, IR and NMR spectra support the donor—acceptor intramolecular interpretation in the ground state of DMAI and MAI.