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131.
Rois Benassi Ugo Folli Silvia Sbardellati Ferdinando Taddei 《Journal of computational chemistry》1993,14(4):379-391
The conformational features of a large number of hydroperoxides ROOH and peroxides ROOR′, where R and R′ are alkyl groups of different and increasing size and phenyl rings, including ortho substituted derivatives, were obtained from molecular mechanics calculations by employing a standard package. For the molecules of small molecular size, comparison was carried out with the results of ab initio calculations. Heats of formation were also obtained from molecular mechanics for hydroperoxides and peroxides: The values are, in general, overestimated. For the molecules containing the CF3 group, the calculated values are subject to large errors and heats of formation were obtained from ab initio total energies in the “atom equivalents” scheme. To estimate the homolytic dissociation energies of the different bonds in the peroxide molecules, heats of formation of R·, ·OR, and ·OOR radicals were employed and several of them had to be calculated. Different approaches were employed—molecular mechanics calculations, ab initio energies within the atom equivalent and isodesmic reaction schemes, and Benson's group additivity rule; values consistent within the different calculation methods were chosen for estimating dissociation energies. The bond dissociation energies indicate different trends in these molecules as a function of the nature of the R and R′ groups and the possible electronic effects operating in these molecules are discussed. © 1993 John Wiley & Sons, Inc. 相似文献
132.
Laurent De Buyck Franco Ghelfi Ugo M. Pagnoni Mariella Pattarozzi Fabrizio Roncaglia 《Tetrahedron》2005,61(11):2871-2877
The rearrangement of a trichloro-pyrrolidin-2-one, prepared by the CuCl-TMEDA catalyzed atom transfer radical cyclization of N-alkyl-N-(3-chloro-2-propenyl)-2,2-dichloromyristamide, with n-propylamine or CH3ONa/CH3OH, is the key step of a new, short and inexpensive route to chaetomellic anhydride C and (±)-erythro-roccellic acid. 相似文献
133.
Ugo Azzena Giovanna Dettori Caterina Lubinu Alberto Mannu Luisa Pisano 《Tetrahedron》2005,61(36):8663-8668
Reduction of 1,2-diaryl-substituted ethenes with Na metal in dry THF allowed easy access to a variety of 1,2-diaryl-1,2-disodiumethanes. These diorganometallic intermediates were elaborated into the corresponding 1,2-diarylethanes (aqueous work up), or cycloalkylated with 1,3-dichloropropanes. The last reaction led to a highly diastereoselective synthesis of trans-1,2-diaryl-substituted cyclopentanes. 相似文献
134.
Paolo Lazzeretti Beniamino Cadioli Ugo Pincelli 《International journal of quantum chemistry》1976,10(5):771-780
Coupled and uncoupled Hartree–Fock theories are used to compute the electric dipole polarizability of water, ammonia, and methane with three different GTO basis sets. Bounds for the geometric approximation to uncoupled polarizabilities are also computed to examine the accuracy of calculated values. The results are compared with those obtained by a variational-perturbation method proposed by Rebane. The numerical tests provide some information on the correlation terms affecting total computed polarizabilities. The computed values are shown to be in fair or good agreement with experimental data for the largest basis sets. The reliability of Rebane's method with respect to coupled HF procedure is also discussed. 相似文献
135.
The temperature dependence of limiting apparent molal volumes ° in water for some alcohols (methanol, ethanol, 1-propanol, 2-butanol, 3-pentanol, 3-hexanol, 2,5-hexanediol, cyclopentanol, cyclohexanol, cycloheptanol, and 1,4-cyclohexanediol) and ethers (trimethylene oxide, tetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, 1,3-dioxepane, 1,3,5-trioxane, dimethoxymethane, 1,2-dimethoxyethane, diethoxymethane, and diethyl ether) has been studied in the temperature range 10–50°C by means of an automatic digital-readout dilatometer. Values of the thermal expansion coefficient * = (1/°)(°/T)p have been obtained at several temperatures and discussed together with literature data on expansibilities of related compounds. The data show a wide spectrum of values of * at low temperatures which is narrowed at the higher ones. The expansibilities of monofunctional alcohols increase with increasing temperature; the opposite effect is observed for polyhydric alcohols. The *'s of ethers are very slightly temperature dependent and are much higher, at low temperature, than those of alcohols having the same ratio ofn
o/nc. These results are discussed in terms of solutewater interactions, and a possible interpretation is put forward. 相似文献
136.
Antonino Corsaro Ugo Chiacchio Venerando Pistarà Roberto Romeo Felicia D'Andrea Emanuele Attolino 《Tetrahedron》2004,60(17):3787-3795
Completely protected 4-deoxy-α-L-threo-hex-4-enopyranosides 1c,d undergo the dichlorocarbene addition affording exclusively diastereomeric adducts 5c,d with the cyclopropane ring anti to the C-3 alkyloxy substituent, while the reaction with 3-unprotected derivatives 1a,b affords a mixture of syn and anti derivatives. Under the Simmons-Smith cyclopropanation adducts 2a-d with a syn stereochemistry are obtained. Starting from 5b, the cyclopropanated sugar 3b is obtained by reduction with LiAlH4, thus the two diastereomers 2b and 3b can be stereoselectively obtained through the two different pathways. For a useful comparison, 4-deoxy-β-L-threo-hex-4-enopyranoside 1e was also subjected to the above two cyclopropanation methods affording the expected cycloadduct 2e and a diastereomeric mixture of dichlorocycloadducts 4e and 5e (4e/5e=2.8:1). 相似文献
137.
Brian T. Heaton Luciano Longhetti D. Michael P. Mingos Clive E. Briant Peter C. Minshall Brian R.C. Theobald Luigi Garlaschelli Ugo Sartorelli 《Journal of organometallic chemistry》1981,213(1):333-350
The crystal structures of Rh4(CO)10(PPh3)2 and Rh4(CO)9P(OPh)33 are reported. 31P-1H NMR studies on Rh4(CO)12-x {P(OPh)3}x(X 1, 2 and 3) show that each derivative exists as only one isomer in solution whereas the analogous triphenylphosphine derivatives can exist as different isomers. A quantitative redistribution of triphenylphosphites occurs on mixing Rh4-(CO)12-xLx with Rh4(CO)12-yLy (L P(OPh)3; x 0, 1, 2, y x + 2; x 0, y x + 4) to give Rh4(CO)12-zLz[z (x + y)]; a related rapid intermolecular randomisation of carbonyls occurs on mixing Rh4(12CO)12 with Rh4(13CO)12. 相似文献
138.
Rosita Diana Ugo Caruso Francesco Silvio Gentile Luigi Di Costanzo Barbara Panunzi 《Molecules (Basel, Switzerland)》2021,26(23)
In the field of optical sensors, small molecules responsive to metal cations are of current interest. Probes displaying aggregation-induced emission (AIE) can solve the problems due to the aggregation-caused quenching (ACQ) molecules, scarcely emissive as aggregates in aqueous media and in tissues. The addition of a metal cation to an AIE ligand dissolved in solution can cause a “turn-on” of the fluorescence emission. Half-cruciform-shaped molecules can be a winning strategy to build specific AIE probes. Herein, we report the synthesis and characterization of a novel L-shaped fluorophore containing a benzofuran core condensed with 3-hydroxy-2-naphthaldehyde crossed with a nitrobenzene moiety. The novel AIE probe produces a fast colorimetric and fluorescence response toward zinc (II) in both in neutral and basic conditions. Acting as a tridentate ligand, it produces a complex with enhanced and red-shifted emission in the DR/NIR spectral range. The AIE nature of both compounds was examined on the basis of X-ray crystallography and DFT analysis. 相似文献
139.
Fabio Borbone Ugo Caruso Antonella De Maria Michela Fusco Barbara Panunzi Antonio Roviello 《Macromolecular Symposia》2004,218(1):313-322
A series of new metal containing polymers for second order nonlinear optics have been prepared by grafting Cu (II) and Pd (II) chromophoric complexes on a preformed (4-vinylpyridine-styrene) copolymeric backbone. The metallated polymers have been chemically and physically characterized. They show high glass transition temperatures, high thermal stability and good solubility. Their properties have been compared with analogous metallated poly(4-vinylpyridine) samples: variations in the polymeric backbone, as well as in ligands, metal, and metallation ratio, allow to tune their properties. 相似文献
140.