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991.
The addition of carboxylic acids to dimethylamino-propinal ( 1a ) and 4-dimethyl-amino-but-3-in-2-on ( 1b ) gives, after rearrangement of the very instable primary adducts ( 2 ), Z-3-acetoxy-N,N-dimethylacrylamides and -crotonamides 3 to 8 in excellent yields and in a stereospecific manner. Similarly, the adducts of HCl and HBr to the alkynes 1a and 1b may be rearranged at low temperature by traces of acid to cis/trans equilibria of 3-halo-acrylamides and -crotonamides 9 and 10 . - On the other hand, treatment of 3-alkoxy-3-dimethylaminoacrolein with traces of acid yields alkylesters of E-3-dimethylaminoacrylic acid ( 12 , X = OR). - The preparative aspects of the rearrangement are discussed, and a brief outline of the spectroscopic properties of the compounds 3 to 8 is given. 相似文献
992.
Mono(6-deoxy-dimethylpyridinium)-β-cyclodextrins have been synthesized in reaction of mono (p-toluenesulfonyl) derivative
of β cyclodextrin with the appropriate lutidine under microwave irradiation and conventional conditions. The results indicate
that the mechanism consists of inclusion complex formation. 相似文献
993.
Yong-Sam Chung Sun-Ha Kim Moon Jong-Hwa Young-Jin Kim Jong-Myoung Lim Jin-Hong Lee 《Journal of Radioanalytical and Nuclear Chemistry》2005,267(1):95-107
Summary As part of an air pollution monitoring study, airborne particulate matter (PM2/PM10-2) samples were collected from 2000 to 2003 at two sampling sites in an urban region, Daejeon, the middle of Korea. Mass concentrations
of both fine and coarse fractions and that of the black carbon in the fine particles were measured using the Gent stacked
filter unit sampler and the smoke stain reflectometer, respectively. In the collected samples the concentrations of 24 elements
were analyzed using instrumental neutron activation analysis. Monitored data were investigated for their temporal trends under
different environmental conditions and their seasonal correlation patterns. Crustal enrichment factors were also estimated
to establish the contribution between anthropogenic and crustal origin. Patterns for airborne particle matter (APM) and elemental
concentrations, seasonal variation of some marker elements were investigated. The results can be applied for the investigation
of further air pollution sources and for the evaluation of air quality. 相似文献
994.
Pérez J Morales D Nieto S Riera L Riera V Miguel D 《Dalton transactions (Cambridge, England : 2003)》2005,(5):884-888
Cationic complexes [Mo(eta(3)-allyl)(CO)2L3]+ (L3 = either nitrogen-donor tridentate ligand or three monodentate ligands) were prepared in high yield and under mild conditions using as precursors either the triflato complex [Mo(eta(3)-allyl)(OTf)(CO)2(NCMe)2] or the combination of the chloro complex [Mo(eta(3)-allyl)Cl(CO)2(NCMe)2] and the salt NaBAr'(4)(Ar'= 3,5-bis(trifluoromethyl)phenyl). The tridentate ligands employed were 2,2':6',2'-terpyridine (terpy) and cis,cis-1,3,5-cyclohexanetriamine (CHTA), whereas the monodentate ligands imidazole (im) and 3,5-dimethylpyrazole (dmpz) were chosen. In order to stabilize the labile intermediates, an excess of acetonitrile was used in most of the syntheses. However, the pyrazole complex was prepared through a nitrile-free route to avoid reactions at the coordinated nitrile. The solid state structures of [Mo(eta(3)-methallyl)(CO)2(terpy)]OTf (2), [Mo(eta(3)-methallyl)(CO)2(CHTA)]BAr'4 (3), [Mo(eta(3)-methallyl)(CO)2(NCMe)3]BAr'4 (4), [Mo(eta(3)-allyl)(CO)2(im)3]OTf (5) and [Mo(eta(3)-allyl)(CO)2(dmpz)3]BAr'4 (6) were determined by means of single-crystal X-ray diffraction. 相似文献
995.
From the de Broglie matter wave hypothesis and Planck’s energy quantization law, and assuming conservation of energy in the
absorption of a photon and its consequent conversion to kinetic energy of motion by a material particle initially at rest,
one can deduce a simple mathematical relationship between the wavelength λ (or frequency ν), of the photon absorbed by the
particle at rest, and the resulting de Broglie matter wave length, λD, of the particle with kinetic energy of motion of mv2/2. The relationship so deduced, λD∝√λ, suggests that visible wavelengths of light, from about 4000 ?, in the violet, to beyond about 7000 ?, in the red, on
absorption by an electron at rest, lead to material electron wavelengths, λD, of the order of the size of the electron transfer proteins seen in the photosynthetic reaction centers of photosynthesizing
organisms, at about a size of 50–100 ?. In addition to understanding the mechanism of photosynthesis as a material wave mediated
phenomenon, further areas of importance of the relations pointed out in this paper are in the design of experiments to gain
a deeper understanding of the basic tenets of wave mechanics, and in the use of tunable lasers to probe various properties
of material waves, and to precisely control their properties for applications including lithography. 相似文献
996.
The spironaphthalen-2-ones 2, 10 and 18 were prepared by N-bromosuccinimide (NBS) oxidation of 1, 9 and 17 respectively, whereas spironaphthalen-1-ones 24 and 25 were obtained by treating 23 with NBS. The stereoisomeric reduction products 29, 30 and 32 obtained from 24 and 25 , gave the pentacyclic compound 33 on treatment with polyphosphoric acid. 相似文献
997.
Two push-pull-cyclobutadienes 10b and 10c are prepared by reaction of two eq. of the corresponding acetylenes having electrondonating and electronaccepting groups ( 4 ) with one eq. of HBF4 to cyclic cyanine salts, followed by elimination of HBF4 with KOC(CH3)3. These cyclobutadienes, stable in cristalline form at room temperature respectively for a short time ( 10b R?CH3) or for several days ( 10c R?OCH3), are extremely reactive in solution towards various nucleophiles and electrophiles. Cleavage of the nascent cyclobutenes leads to butadienes. The cyclobutadienes 10 dimerise thermally to cyclooctatetraenes 18 . 相似文献
998.
Photodynamic therapy (PDT) relies on three main ingredients, oxygen, light and photoactivating compounds, although the PDT response is definitively contingent on the site and level of reactive oxygen species (ROS) generation. This study describes the development of a novel, fluorescent-based actinometer microsphere system as a means of discerning spatially resolved dosimetry of total fluence and ROS production. Providing a high resolution, localized, in situ measurement of fluence and ROS generation is critical for developing in vivo PDT protocols. Alginate-poly-L-lysine-alginate microspheres were produced using ionotropic gelation of sodium alginate droplets, ranging from 80 to 200 microm in diameter, incorporating two dyes, ADS680WS (ADS) and Rhodophyta-phycoerythrin (RPE), attached to the spheres' inside and outside layers, respectively. To test the responsivity and dynamic range of RPE for ROS detection, the production of ROS was initiated either chemically using increasing concentrations of potassium perchromate or photochemically using aluminum tetrasulphonated phthalocyanine. The generation of singlet oxygen was confirmed by phosphorescence at 1270 nm. The resulting photodegradation and decrease in fluorescence of RPE was found to correlate with increased perchromate or PDT treatment fluence, respectively. This effect was independent of pH (6.5-8) and could be inhibited using sodium azide. RPE was not susceptible to photobleaching with light alone (670 nm; 150 Jcm(-2)). ADS, which absorbs light between 600 and 750 nm, showed a direct correlation between radiant exposure (670 nm; 0-100 Jcm(-2)) and diminished fluorescence. Photobleaching was independent of irradiance (10-40 mW cm(-2)). We propose that actinometer microspheres may provide a means for obtaining high spatial resolution information regarding delivered PDT dose within model systems during investigational PDT development and dosimetric information for clinical extracorporeal PDT as in the case of ex vivo bone marrow purging. 相似文献
999.
Daniel M. Chipman 《Theoretical chemistry accounts》1989,76(2):73-84
Summary The suitability of Gaussian basis sets for ab initio calculation of Fermi contact spin densities is established by application to the prototype first-row atoms B-F having open shell p electrons. Small multiconfiguration self-consistent-field wave functions are used to describe relevant spin and orbital polarization effects. Basis sets are evaluated by comparing the results to highly precise numerical grid calculations previously carried out with the same wave function models. It is found that modest contracted Gaussian basis sets developed primarily for Hartree-Fock calculations can give semiquantitative results if augmented by diffuse functions and if further uncontracted in the outer core-inner valence region. 相似文献
1000.
E. M. Araújo Renata Barbosa Amanda D. Oliveira Crislene R. S. Morais T. J. A. deMélo A. G. Souza 《Journal of Thermal Analysis and Calorimetry》2007,87(3):811-814
Polyethylene/montmorillonite clay nanocomposites were obtained via direct
melt intercalation. The clay was organically modified with four different
types of quaternary ammonium salts. The objective of this work is to study
the use of montmorillonite clay in the production of nanocomposites by means
on rheological, mechanical and crystallization properties of nanocomposites
and to compare to the properties of the matrix and PE/unmodified clay nanocomposites.
In general, the tensile test showed that the yield strength and modulus of
the nanocomposites are close to the pure PE. Apparently, the mixture with
Dodigen salt seems to be more stable than the pure PE and PE/unmodified clay. 相似文献