Papers by Oronzo Sciacovelli
Spectrochimica Acta Part A: Molecular Spectroscopy, 1985
An analysis of the 1H and 19F NMR spectra of 2-fluoronaphthalene was performed. 1H19F inter-ring... more An analysis of the 1H and 19F NMR spectra of 2-fluoronaphthalene was performed. 1H19F inter-ring coupling constants were found to be positive over an even number of intervening bonds between the coupled nuclei and negative over an odd number. Such a sign alternation was based on a positive value for the hyperfine interaction constant of the fragment CF. Theoretical computation based on the finite perturbation theory (FPT) in the MO INDO approximation gives 1H19F inter-ring coupling constant values which are in satisfactory agreement with the experimental ones. 1H1H coupling constants follow the expected trend.
Chemischer Informationsdienst, 1975
ChemInform Abstract Austauschreaktionen an (I) werden kinetisch diskutiert.
Chemischer Informationsdienst, 1978
ChemInform Abstract Die Reduktion der Titelverbindung (I) in saurer alkoholischer Lösung ergibt e... more ChemInform Abstract Die Reduktion der Titelverbindung (I) in saurer alkoholischer Lösung ergibt ein Produktgemisch (Ausb.-Angabe in g), das 2 Komponenten mit sehrähnlichen Rf-Werten enthält (60% bzw. 40%), denen mit Hilfe der INDOR-Technik die Strukturen (II) und (III) zugewiesen werden.
Inorganic Chemistry, 2005
Dynamic NMR experiments on trans-[Pt(Cl)(PHCy 2) 2 {P(X)Cy 2 }] z where X is a lone pair (1, z) 0... more Dynamic NMR experiments on trans-[Pt(Cl)(PHCy 2) 2 {P(X)Cy 2 }] z where X is a lone pair (1, z) 0), H (2, z) +1), S (3, z) 0), or O (4, z) 0) show that the rotation around the P(X)−Pt bond is hindered for all molecules studied, with ∆G q ranging from 8.2 to 11.0 kcal/mol. The highest value of the series was calculated for trans-[Pt(Cl)-(PHCy 2) 2 {P(O)Cy 2 }] (4) where intramolecular PdO‚‚‚H−P interactions act as a molecular brake at room temperature. Single-crystal X-ray diffraction confirms the presence of both intra and intermolecular PdO‚‚‚H interactions in solid 4. In the case of [Pt(Cl)(PHCy 2) 3 ]Cl, multinuclear NMR analysis indicates the presence of a P−H‚‚‚Clinteraction in aromatic or halogenated solvents which could have also a minor effect on the rotational barrier around the P(X)−Pt bond.
Arkivoc, 2009
17 O NMR Substituent Chemical Shift (SCS) values on the carbonyl and methoxy oxygens in methyl 2,... more 17 O NMR Substituent Chemical Shift (SCS) values on the carbonyl and methoxy oxygens in methyl 2,6-dimethyl-4-X-benzoates 2' have been measured in acetonitrile-d 3 and compared with those of the 2,6-unsubstituted methyl 4-X-benzoates 2, the former exhibiting very little sensitivity to the effect of 4-substituents and not appearing to be related to π-electron density changes in such sterically hindered systems. Conversely 13 C NMR SCS values of the methoxy carbon of the ester function in either 2 and 2', although modest in size, exhibit a very good dual substituent parameter (DSP) correlation with the polar and resonance effect of 4-substituents and are therefore effective indicators of local πelectron densities. Moreover, 13 C NMR SCS values of the methoxy carbon of 2' exhibit an excellent linear correlation with those of 2,6-unsubstituted benzoates 2. Once more this agrees with our previous conclusion that the resonance interaction between the aromatic ring and the ester group is essentially related to a π-polarization effect, not involving charge-transfer between the two moieties and therefore not sensitive to steric hindrance to their coplanarity.
Chemischer Informationsdienst
Zeitschrift für Naturforschung. Section C: Biosciences
The tautomerism of phenylpyruvic acid (PPA) and its sodium salt was investigated. The 1H and 13C ... more The tautomerism of phenylpyruvic acid (PPA) and its sodium salt was investigated. The 1H and 13C spectra of PPA in aprotic solvents and in methanol show almost complete prevalence of the enol form, whereas the keto form prevails only in water. The Z configuration was assigned to the sole enol tautomer present on the basis of the value of the vicinal coupling constant [3J1H, 13COOH]=3.7 Hz. A small amount of the hydrated form of PPA (1-phenyl-2, 2-dihydroxylpropanoic acid) was found in the aqueous solution of its sodium salt and in buffer solution (pD=6) of PPA. By means of infrared spectroscopy one can conclude that crystalline PPA is in the enol whereas its sodium salt is in the keto form. The keto-acid was not obtained in the solid state. The colorimetric method for testing PPA traces in urine depends on the formation of a enol-Fe3+ complex (2:1) which appears stable in dimethylsulfoxide (DMSO).
Clinica Chimica Acta International Journal of Clinical Chemistry, Jan 12, 1978
A simple alternative colorimetric method has been developed for quantitative determination of phe... more A simple alternative colorimetric method has been developed for quantitative determination of phenylpyruvic acid in urine based on the improved stability of the ferric complex of enol-phenylpyruvate in water-dimethylsulfoxide 50% vol. mixed solvent. The method can be applied directly to urine or to a dry ether-extract of urine. Operating on the dry ether-extract of urine, detection of phenylpyruvic acid is possible at an amount of as low as 1 mg/100 ml. Whereas, if urine samples are processed, detection is possible for a concentration of as low as 5 mg/100 ml and quantitative determination for a concentration greater than 10 mg/100 ml. The test carried out on a diaper wet with urine retains the same sensitivity and shows instantaneous development of the green colour.
Journal of Molecular Catalysis, 1985
High resolution "0 NMR spectra of "O-labeled t-BuOOH, t-BuOOBu-t, (HMPA)MoO(O~)~ and (L)CrO(O& (w... more High resolution "0 NMR spectra of "O-labeled t-BuOOH, t-BuOOBu-t, (HMPA)MoO(O~)~ and (L)CrO(O& (with L = HMPA, Py) have been measured. Significant differences were found in the peroxide bond resonances of the chromium with respect to the molybdenum peroxo complex, in that chromium(VI)o diperoxide showed two distinct "0 resonance signals, suggesting non-equivalence of the oxygen atoms in the O-O bond; this feature was not present in the spectra of (HMPA)MoO(O& For both peroxometal complexes, no "0 NMR evidence could be found for significant exchange between 0x0 and peroxo oxygens.
Inorganica Chimica Acta, Jul 16, 1990
The reaction of the complexes Pt(PPh,),(OOH)X (HX = succinimide (I), phthalimide (II), PhOH (III)... more The reaction of the complexes Pt(PPh,),(OOH)X (HX = succinimide (I), phthalimide (II), PhOH (III), p-MeC6H40H (IV)) and Pt(PPh,),(OH)X (HX = succinimide (V), phthalimide (VI)) with CO and CO* have been studied. In order to clarify some reaction pathways, the reactivity of Pt [0,C(0)O](PPh3)2 (VII) and of Pt[O,CMe,~](PPh& (VIII) with succinimide and phthalimide has also been investigated. I70 NMR and IR spectra of some of these compounds and of Pm](PPh,), (IX) have been recorded. to the olefin [l]. However, on considering the growing interest in the chemistry of monomeric metal hydroxides, alkoxides and amides [2], we decided to investigate the reactivity of compounds I-VI towards carbon oxides. Moreover, in order to (PPh,), (VIII) with succinimide and phthalimide has also been investigated. I70 NMR and IR spectra of some of these compounds and of Pt [OC(O)o]-(PPh3)* (IX) are also reported and discussed.
J Am Chem Soc, 1981
We sought a thiocarbonyl reagent that could be introduced by simple acylation. A second considera... more We sought a thiocarbonyl reagent that could be introduced by simple acylation. A second consideration was that the intermediate radical species resulting from attack of tin at thione sulfur would not be stabilized at the a-carbon. Such a stabilization could allow abstraction of hydrogen from the trialkylstannane to compete effectively with alkyl carbon-oxygen bond homolysis. Dethiation (thiobenzoyl esterbenzyl ether) and collapse (dithiocarbonate esteralcohol starting material) byproducts have been observed by using the a-benzylic-and a-thiol-stabilized ~p e c i e s .~~*~~~ Treatment of thiophosgene with phenol gave phenyl chloro-thionocarb~nate.'~ Pyridine effectively catalyzed reactions of this thioacyl chloride with relatively unhindered alcohols, but 4-(dimethy1amino)pyridine was requiredl6 for smooth conversion of nucleosides to their 2'-O-phenoxythiocarbonyl derivatives.
Journal of the Chemical Society Chemical Communications, 1981
Magn Reson Chem, 2006
33S NMR parameters (chemical shifts and linewidths) in 2-substituted sodium ethanesulfonates, XCH... more 33S NMR parameters (chemical shifts and linewidths) in 2-substituted sodium ethanesulfonates, XCH2CH2SO3Na (X = H, CH3, OH, SH, NH2, Cl, Br, NH3+) depend upon the electronic properties of substituents. To explain experimental results and obtain additional information on the origin of the observed substituent effect (SE), sulfur isotropic absolute shielding constants have been calculated at DFT level of theory (B3LYP/6-311++G(2d,p)) by gauge-including atomic orbitals (GIAO) method. Data have been interpreted with the aid of natural bond orbital (NBO) method and natural chemical shielding (NCS) analysis. It has been demonstrated that in the class of compounds considered the diamagnetic contribution to sulfur-shielding constant is constant and the observed upfield shift of 33S resonance induced by electron-withdrawing substituents (reverse chemical shift effect) can be related to variations of the paramagnetic contribution. Substituents with different electronic properties cause variations in the polarization of S-C and S-O bonds of the -C-SO3- moiety thus determining changes of the electron density at sulfur nucleus and consequently the expansion or contraction of 3p sulfur orbitals. Also oxygen lone-pairs and sulfur core 2p electrons can play an active role in determining the paramagnetic contribution to sulfur shielding. With regard to linewidth variations, they can be ascribed primarily to changes in the nuclear quadrupole coupling constant values. B3LYP/6-311++G(2d,p) method allows obtaining a good reproducibility of SE on the electric field gradient (EFG) at sulfur, although its values tend to be underestimated significantly. Moreover, 17O shielding constants have been calculated.
Chemischer Informationsdienst, 1975
Chemischer Informationsdienst, 1973
J Org Chem, 1987
Sir: During the last decade we have collected kinetic, ls0-labeling, and stereochemical data that... more Sir: During the last decade we have collected kinetic, ls0-labeling, and stereochemical data that stringently suggest dioxiranes-ie, the smallest ring peroxide species containing carbon-are generated in the reaction of po-tassium peroxymonosulfate (caroate) with Recently, the case for the ...
Journal of the Chemical Society Perkin Transactions 2
Journal of the Chemical Society, Perkin Transactions 2, 1980
ABSTRACT
Organic Magnetic Resonance, 1979
The complete 'H NMR spectral analyses of quinoline and two of its derivatives (4,7-dichloroquinol... more The complete 'H NMR spectral analyses of quinoline and two of its derivatives (4,7-dichloroquinoline and 8-11itroqUinoline) have been performed. AU the long-range coupling constants were determined both in magnitude and sign. In determining the signs the INDOR technique was very useful and successful, allowing the resolution of transitions as close as a few hundredths of a Hz. The signs of the interring coupling constants alternate with the number of intervening bonds, according to MccoMe~'s rule, except the all-traos 6J couplings. A h e a r relationship has been found between the 'H-'H and %-' % interring coupling constants for which the spin polarization is transmitted almost exclusively via the ?r-electron system.
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Papers by Oronzo Sciacovelli