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101.
102.
This is the first part of a study of the local field effects on (non)linear optical susceptibilities of solutions of para-nitroaniline (pNA) in three different solvents, cyclohexane (CH), 1,4-dioxane (DI), and tetrahydrofuran (THF), using a discrete molecular representation of the condensed phase. To account for dipolar and quadrupolar effects, the latter of which are especially important for DI solution, all the electric properties necessary to compute the local fields and local field gradients in quadrupolar approximation as well as the dipolar hyperpolarizabilities for the four molecules are computed, including frequency dispersion and vibrational contributions to the dipolar properties. The convergence of the perturbation treatment for the pure vibrational (PV) contributions is examined by comparison of the values obtained at the lowest order with those of partially computed second order in mechanical and electrical anharmonicity. For pNA, for which previous computations of the hyperpolarizabilities have generally found poor agreement with experimental results, a thorough investigation of the effects of solvent-induced geometry changes, dynamic and static correlation, frequency dispersion, and classical thermal averaging over the torsional modes of the substituent groups and the inversion mode of the amino group on the dipolar properties is carried out. Computations using self-consistent continuum reaction field models show that the amino group is substantially less pyramidalized in polar solvents than in the gas phase. With all the effects taken into account, reasonable agreement with the experimental electric-field induced second harmonic generation (EFISH) result on pNA vapor of Kaatz, Donley, and Shelton is obtained. 相似文献
103.
We report the results of coupled Hartree-Fock computations for the average polarizability, , and hyperpolarizability, , of CH4, C2H6, C3H6 and C3H8. The Hamiltonian matrices are constructed from an extended CNDO model. Small as well as large basis sets were tested. Agreement with available experimental values is within 13% for and 31% for . 相似文献
104.
Ethyl N-(2-methoxycarbonylphenyl)thiocarbamate ( 2), N -(2-ethoxycarbonylphenyl)-4-methoxythiobenz-amide ( 3b ), and 2-(4-methoxyphenyl)-4H-3,1-benzothiazin-4-one ( 4a ), react with nucleophilic reagents containing at least one primary amino group to yield a variety of 2-substituted and 2,4-disubstituted 4(3H)quinazolinones, as well as some tricyclic and tetracyclic products. 相似文献
105.
Karagiorgou O Patsis G Pelecanou M Raptopoulou CP Terzis A Siatra-Papastaikoudi T Alberto R Pirmettis I Papadopoulos M 《Inorganic chemistry》2005,44(12):4118-4120
The reaction of fac-[NEt(4)](2)[Re(CO)(3)Br(3)] with (S)-(2-(2'-pyridyl)ethyl)cysteamine, L(1), in methanol leads to the formation of the cationic fac-[Re(CO)(3)(NSN)][Br] complex, 1, with coordination of the nitrogen of the pyridine, the sulfur of the thioether, and the nitrogen of the primary amine. When fac-[NEt(4)](2)[Re(CO)(3)Br(3)] reacts with the homocysteine derivative (S)-(2-(2'-pyridyl)ethyl)-d,l-homocysteine, L(2), the neutral fac-Re(CO)(3)(NSO) complex, 2, is produced with coordination of the nitrogen of the primary amine, the sulfur of the thioether, and the oxygen of the carboxylate group, while the pyridine ring remains uncoordinated. The analogous technetium-99m complexes, 1' and 2', were also prepared quantitatively by the reaction of L(1) and L(2) with the fac-[(99m)Tc(CO)(3)(H(2)O)(3)](+) precursor at 70 degrees C in water. Given that both (S)-(2-(2'-pyridyl)ethyl)cysteamine and homocysteine can be easily N- or S-derivatized by a bioactive molecule of interest, both the NSN or NSO ligand systems could be used to develop target-specific radiopharmaceuticals for diagnosis and therapy. 相似文献
106.
K Papadopoulos T TriantisC.H Tzikis A NikokavouraD Dimotikali 《Analytica chimica acta》2002,464(1):135-140
A weak chemiluminescence (CL) emission was observed in commercial Greek extra virgin olive oils (Knossos, Spitiko, Ananias, Altis, Minerva, Xenia) and in refined seed oils such as sunflower oils (Marata, Sanola, Sun, Mana, Sol, Minerva) as well as in corn oils (Flora, Minerva, Marata Sun and Sol) with potassium superoxide in the aprotic solvent dimethoxyethylene.On measuring the CL of mixtures of extra virgin olive oils with the cheaper refined seed oils, calibrations were produced which can be used for the determination of the adulteration of olive oils with seed oils down to 3%. Furthermore, depending on the kind of oils, “low” authenticity-CL-factors for olive oils (0.8-2.15 μmol l−1 gallic acid) and “high” for seed oils (4.5-11.2 μmol l−1 gallic acid) were calculated. 相似文献
107.
Room temperature treatment of 2-(3-arylureido)benzoic acids ( 1 ) and methyl 2-(3-alkyl-, or 3-arylureido)- benzoates ( 2 ) with concentrated sulfuric acid leads to N-substituted 2-amino-4H-3,l-benzoxazin-4-ones ( 3 ) in generally very good yields. The isomeric 3-substituted 2,4(1H,3H)-quinazolinediones ( 4 ) are conveniently made in high yield by the action of aqueous-ethanolic sodium hydoxide on 2. 相似文献
108.
Wen L Cheng J Zou H Zhang L Chen J Papadopoulos KD 《Langmuir : the ACS journal of surfaces and colloids》2004,20(19):8391-8397
A mathematical model for analyzing the van der Waals interaction between the internal aqueous droplets (W(1)) and the external aqueous phase (W(2)) of double emulsions has been established. The effects of Hamaker constants of the materials forming the system, especially those of the two different adsorbed surfactant layers with uniform density (A(1) and A(2)), on the van der Waals interaction were investigated. The overall van der Waals interaction across the oil film is a combined result of four individual parts, that is, W(1)-W(2), A(1)-A(2), W(1)-A(1), and A(2)-W(2) van der Waals interaction, and it may be either attractive or repulsive depending on many factors. It was found that the overall van der Waals interaction is dominated by the W(1)-W(2) interaction at large separation distances between the W(1)/O and O/W(2) interfaces, while it is mostly determined by the A(1)-A(2) interaction when the two interfaces are extremely close. Specifically, in the cases when the value of the Hamaker constant of the oil phase is intermediate between those of W(1) and W(2) and there is a thick oil film separating the two interfaces, a weak repulsive overall van der Waals interaction will prevail. If the Hamaker constant of the oil phase is intermediate between those of A(1) and A(2) and the two interfaces are very close, the overall van der Waals interaction will be dominated by the strong repulsive A(1)-A(2) interaction. The repulsive van der Waals interaction at such cases helps stabilize the double emulsions. 相似文献
109.
An optical video microscopic technique was used to study hetero-aggregation and selective aggregation phenomena among n-hexadecane oil drops (40–110 μm in diameter) and two types of polystyrene latex particles (6.76 and 30.2 μm, in diameter),
suspended inside an aqueous medium with pH varying between 1.1 and 12.9. A single drop was produced in situ using a micropipette
inside the aqueous phase-filled glass microcapillary (100–160 μm i.d.) containing the particles. Interactions between the
drop and the solid particles and among the solid particles was achieved by movement of the aqueous medium in and out of a
second micropipette. Drop–particle interactions were distinctly different from particle–particle interactions. It was observed
that the latex particles aggregated irreversibly with the oil drop in all cases except two, viz. for 6.76 μm particles at
around neutral pH whereas the irreversibility of aggregation in particle–particle interactions was only seen at the ends of
the pH spectrum. At around neutral pH, the flocs or clusters of small particles were very weak. Visual observations at each
pH are explained on the basis of the classical DLVO (Derjaguin–Landau–Verwey–Overbeek) theory. Partial wetting of particles
surfaces by oil appears to be a key factor in the irreversibility of drop– particle hetero-aggregation. Results indicate that
the display of reversible, irreversible or weak aggregation depends on the location and depth of the secondary minimum and
that the long-range, attractive, London–van der Waals force is responsible for the initial formation of an aggregate.
Received: 4 July 1996 Accepted: 5 December 1996 相似文献
110.
Eleftherios Paul Papadopoulos 《Journal of heterocyclic chemistry》1981,18(3):515-518
Anthranilonitrile reacts with ethyl isocyanatoacetate to form 2-(3-ethoxycarbonylmethylureido)benzonitrile (3b) which, upon heating, or treatment with a base, undergoes a double cyclization to yield imidazo[1,2-c]-quinazoline-2,5-(3H,6H)dione ( 5 ) in excellent yield. In the presence of acid, 3b is converted into 1,4-dihydro-2,4-dioxo-3-(2H)quinazolineacetic acid ( 11 ), or its ethyl ester ( 10 ). The action of concentrated sulfuric acid converts the adduct 13 of anthranilic acid and ethyl isocyanatoacetate into 2-ethoxycarbonyl-methylamino-4H-3,1 -benzoxazin-4-one ( 14 ). 相似文献