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2.
Robert Shaw 《国际化学动力学杂志》1973,5(2):261-269
Heats of formation of solid, liquid, and gaseous nitroalkanes have been shown mostly to obey group additivity. Group values have been obtained for carbon atoms attached to one, two, and three nitro groups. The heat of formation of 1,1,1,3,5,5,5,-heptanitropentane, either solid or liquid, cannot be fitted to the scheme, even allowing for gauche effects. The differences between observed and estimated values for 1,1,1-fluorodinitroalkanes and 1,2-dinitroethane are larger than expected and should be further investigated. Activation energies have been calculated for decomposition by five-center elimination of HONO from mononitro- and dinitroalkanes using thermochemistry and estimated activation energies for the reverse reactions. The key data for these estimates were previously reported activation energies for the decomposition of nitroethane and 1,2-dinitropropane. The calculations also gave values for the heats of formation (in kcal/mole) of nitroethylene 12.4, and 1-nitropropylene 5.6, and 2-nitropropylene 1.6. Activation energies were calculated for the competing unimolecular reaction, C? N bond fission, from thermochemistry and previously reported activation energies for the decomposition of 1,1- and 2,2-dinitropropane. Comparison of Arrhenius parameters for the two competing processes, namely, HONO and C? N bond fission, shows that, for the geminate dinitroethanes and dinitropropanes, C? N bond fission is faster about 370°K and, for the mononitroalkanes and for all the mononitroalkanes and dinitroalkanes, C? N bond fission is faster above 770°K. 相似文献
3.
Mustafa R. Ibrahim Zacharia A. Fataftah Paul von Ragu Schleyer Peter D. Stout 《Journal of computational chemistry》1987,8(8):1131-1138
Sets of hydrogen molecule equivalents have been developed which permit the calculation of hydrogenation of different types of carbon-carbon bonds from ab initio total energies (3-21G and 6-31G* basis sets, and, to a more limited extent, for MP2/6-31G* data) of reactants and products. The calculated enthalpies of hydrogenation are in good agreement with experiment for unstrained molecules, with average errors on the order of 2 kcal/mol. The 6-31G* equivalents allow the enthalpies for strained molecules to be calculated accurately, but the 3-21G equivalents do not. The equivalents for both basis sets have been tested by calculating the enthalpies of hydrogenation of carbon-carbon bonds in nitrogen- and oxygen-containing organic molecules, free radicals, and classical carbocations. The results are in good agreement with experiment in most cases. 相似文献
4.
栽培草莓品种果实香气特性研究 总被引:15,自引:0,他引:15
通过对4个不同栽培草莓(Fragaria ananassa Duch.)品种果实糖和氨基酸测定及香气的GC-MS分析,结果表明:不同品种间氨基酸和糖含量不同,氨基酸含量由高到低依次为丰香、瓦尔达、哈达和全明星;哈达、丰香、全明星和瓦尔达4个品种果实分别检测出39、46、37和44种香气成分,各占总峰面积98.52%、99.15%、98.77%和95.4l%,检测成分的多少与氨基酸总量显著正相关,相关系数为0.967;哈达有5种独有的成分,丰香有9种独有的成分,全明星有3种独有的成分,瓦尔达有2种独有的成分,4个品种共有的成分有19种。 相似文献
5.
Stepkowska E. T. Perez-Rodriguez J. L. Jimenez de Haro M. C. Sayagues M. J. 《Journal of Thermal Analysis and Calorimetry》2002,69(1):187-204
Main hydration products of two cement pastes, i.e. CSH-gel, portlandite (P) (and specific surface S) were studied by static heating, and by SEM, TEM and XRD, as a function of cement strength (C-33 and C-43) hydration time (th) and subsequent hydration in water vapour.Total change in mass on hydration and air drying, Mo, increased with strength of cement paste and with hydration time. Content of water escaping at 110 to 220°C, defined as water bound with low energy, mainly interlayer and hydrate water, was independent on cement strength but its content increased with (th). Content of chemically bound (zeolitic) water in CSH-gel, escaping at 220-400°C, was slightly dependent on strength and increased with (th). It was possibly derived from the dehydroxylation of CSH-gel and AFm phase. Portlandite water, escaping at 400-500°C, was independent on cement strength and was higher on longer hydration. Large P crystals were formed in the weaker cement paste C-33. Smaller crystals were formed in C-43 but they increased with (th). Carbonate formated on contact with air (calcite, vaterite and aragonite), decomposed in cement at 600-700oC. It was high in pastes C-33(1 month) and C-43(1 month), i.e. 5.7 and 3.3%, respectively; it was less than 1% after 6 hydration months (low sensitivity to carbonation) in agreement with the XRD study showing carbonates in the air dry paste (1month), and its absence on prolonged hydration (6 months) and on acetone treatment. Water vapour treatment of (6 months) pastes or wetting-drying increased this sensitivity.Nanosized P-crystals, detected by TEM, could contribute to the cement strength; carbonate was observed on the rims of gel clusters.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
6.
Influence of viscosity of medium on processes of oxygen quenching of excited states of mesoporphyrin
E. I. Kapinus V. A. Ganzha B. M. Dzhagarov E. I. Sagun V. B. Pavlenko 《Theoretical and Experimental Chemistry》1989,25(2):146-151
The oxygen quenching rate constants for singlet and triplet excited states of the dimethyl ester of mesoporphyrin IX increase with decreasing viscosity of the medium and reach a maximum at a viscosity of approximately 0.4 mPa·sec, after which the rate constants begin to decrease. The drop in rate constant with increasing fluidity of the medium may be related to a nonequilibrium character of the elementary act in the interaction of the reactants in the solvent cage. In viscous media such as isopropyl alcohol, isobutyl alcohol, and isoamyl alcohol, the reaction radius is greater than the sum of the radii of the reacting particles. The long-range character of these processes is due to the relatively weak dependence of the quenching probability on distance.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 2, pp. 161–167, March–April, 1989. 相似文献
7.
In the present investigation,the non-volatile constituents of Danguei (Tang-Kuei) roots of Gansu origin [Angelica sinensis (Oliv.) Diels] were analyzed and thirty seven organic constituin s were also identified,fifteen of which have not been recorded in literature before,including a new optically active compound named as Angelicide and an antibiotie,Brereldin A.By plasma emission spectrometry,thirteen minor elements were also detecled 相似文献
8.
M. A. Bitadze Ts. M. Dalakishvili É. P. Kemertelidze 《Chemistry of Natural Compounds》1992,28(3-4):279-281
The phospholipids of the polar lipids of the seeds of the Judas tree and the fatty-acid composition of the N-acylphosphatidylethanolamines, the phosphatidylcholines, and the phosphatidylethanolamines, and also the molecular-species types of the fatty acids of the phosphatidylcholines and the phosphatidylethanolamines have been studied. It has been established that the seeds of the Judas tree contain ten phospholipids. The main fatty acids are palmitic and oleic.I. V. Kutateladze Institute of Pharmacochemistry, Georgian Academy of Sciences. Translated from Khimiya Prirodnykh Soedinenii, Nos. 3,4, pp. 320–323, May–August, 1992. 相似文献
9.
In a search for compounds that have thermochromic properties, a group of formazans that contain benzimidazolyl (benzothiazolyl), methyl (phenyl), and hydroxydinitrophenyl (anthraquinoyl) groups in the 1-, 3-, and 5-positions, respectively, were synthesized. Benzimidazolylformazans with a picramic acid residue in the 5-position have thermochromic properties.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 970–973, July, 1971. 相似文献
10.
The spectral-polarization characteristics of absorption and phosphorescence of molecules of the initial form of nitro-substituted
indolinospirobenzothiopyran were studied in oriented polyethylene films and in solutions with different polarity. An oscillator
model of the electron transitions responsible for the formation of absorption and luminescence spectra was suggested. It was
established that the principal differences in the spectral and photophysical properties of the compound studied and its oxygen-containing
analog are associated with the fact that the electronegativity of the S atom is lower than that of the O atom.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1143–1146, June, 1997. 相似文献
11.
Yu. A. Tadzhibaev Kh. S. Mukhamedova S. T. Akramov 《Chemistry of Natural Compounds》1978,13(5):517-520
Summary The phospholipid complexes of the seeds ofErysimum diffusum andE. sylvestris have been investigated. It has been found that the amount of phospholipids in the seeds ofE. diffusum is lower than in those ofE. sylvestris, but their qualitative compositions are similar. The fatty-acid compositions of the triglycerides and of the total phospholipids of the two plants investigated have been studied. It has been established that the total phospholipids of the species ofErysimum under consideration and individual fractions of them differ by the degree of saturation and the qualitative and quantitative composition of the acids that they contain and, consequently, the phospholipids present in greatest amount differ in their molecular compositions.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 623–627, September–October, 1977. 相似文献
12.
Zh. K. Tukhmetova Sh. B. Kasenova I. M. Oskembekov S. M. Adekenov B. K. Kasenov Zh. S. Nurmaganbetov 《Russian Journal of Applied Chemistry》2010,83(1):54-57
Catalytic thermal destruction of ethylenediaminetetraacetic acid and its complexes with nickel, iron, and cobalt in nitrate
solutions on carbon materials (activated unwoven material, sibunite, and BAU–A activated carbon) was studied. The activation
energies of thermal destruction were calculated. 相似文献
13.
A. M. Rashkes N. K. Khidyrova M. M. Kiktev U. A. Abdullaev Kh. M. Shakhidoyatov 《Chemistry of Natural Compounds》1997,33(1):89-92
The compositions of the secondary metabolites (SMs) of the leaves and petioles of cotton plants of the deciduous and selection lines L-275, L-470, L-475, and 142-F and the variety Tashkent-1 have been studied. It has been shown that the level of -tocopherol and polyprenols in the leaf blades and petioles changes fairly sharply according to the phases of ontogenesis. The results of an exogenous treatment of the leaves of cotton plants of the control varieties Tashkent-1 and 108-F with the SMs showed an interrelationship of deciduousness and the quantitative composition of the sterols.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 40 64 75. Translated from Khimiya Prirodnykh Soedinenii, Vol. 33, No. 1, pp. 113–117, January–February, 1997. 相似文献
14.
微量钙的测定方法研究进展 总被引:5,自引:0,他引:5
介绍了1995-2006年期间测定微量和痕量钙的方法,如电感耦合等离子体-原子发射光谱法、原子吸收光谱法以及离子色谱法等的工作原理和特点,并说明了其测定微量钙的应用领域。并对微量钙的测定技术进行了展望(引用文献55篇)。 相似文献
15.
R. H. Khachatrian S. V. Sayadian S. A. Hovsepian N. Yu. Grigorian M. H. Injikian 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4)
Abstract The convenient methods of preparation of secondary and tertiary phosphines, phosphinoxides and phosphonates on the basis of corresponding P-H acids and alkyl-, allyl-, alle-nyl-, ethynylarylhalides, 1,3-diens, acetylenic and vinyl-acetylenic hydrocarbons as alkylating agents have been elaborated. The reactions were proceeded in organic solvents in the presence of potassium carbonate under the conditions of interphase catalysis in liquid-liquid, liquid-solid systems, as well as in superbasic medium (schemes 1, 2) 相似文献
16.
S. Ya. Kuchmii B. F. Minaev A. V. Korzhak A. I. Kryukov 《Theoretical and Experimental Chemistry》1997,33(1):16-20
A mechanism of photocatalytic synthesis of chlorohydrins from olefins and peroxo complexes of titanium (IV) is proposed. It
consists of formation of radical-containing complexes, their reactions with olefins, and decomposition of the α-oxides obtained
by hydrogen chlorides.
L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prosp. Nauki, 252039 Kiev,
Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 1, pp. 17–21, January–February, 1997. 相似文献
17.
V. N. Plugar' N. D. Abdullaev Ya. V. Rashkes M. R. Yagudaev N. Tulyaganov 《Chemistry of Natural Compounds》1984,19(6):720-727
The structures of the main components of the total metabolites of the anticholinesterase drug deoxypeganine (DOP) and its analog deoxyvasicinone (DOV) in the rat organism have been studied. The structures of two metabolites of DOP and DOV — 11-hydroxydeoxyvasicinone and 2-(-ethoxycarbonyl)ethyl-4-quinazoline — have been determined by the PMR method. On the basis of their structures and the results of measurements of the elementary compositions of ions, the fragmentation of the compounds has been elucidated. A minor component of the total metabolites has been isolated by chromato-mass spectrometry and for it the structure of 6-methoxydide-hydrovasicinone is proposed. A scheme of the metabolism of DOP and DOV has been put forward.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 758–766, November–December, 1983. 相似文献
18.
V. P. Sitnik N. V. Nekrasov T. V. Vasina V. I. Yakerson O. V. Bragin 《Russian Chemical Bulletin》1990,39(4):641-646
The kinetics of transformations of propane and propylene on pentasils modified with zinc, Zn/HTsVM, and the H form of zeolite were investigated. Quantitative data were obtained which revealed significant differences for HTsVM and Zn-containing catalysts in the selectivity of transformations of propane with different degrees of its conversion. The promoting effect of Zn in the Zn/HTsVM system not only on the stage of dehydrogenation of propane into propylene, but also on subsequent transformations of propylene into aromatic hydrocarbons, was demonstrated. The absence of internal diffusion inhibition of the reaction in the conditions studied was demonstrated experimentally. It was shown that aromatization of propane takes place in the kinetic region.For previous communication, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 727–733, April, 1990. 相似文献
19.
M. Micó A. Labrada S. Calderón 《Journal of Radioanalytical and Nuclear Chemistry》1999,240(2):471-474
X-ray analysis can be used to determine the quality of seeds, showing the cause of bad germination. X-ray images provide information
on the internal structure and morphology of seeds, mechanical damage, percentage of empty and filled seeds, microfractures,
possible embryo deformations and insect infestation. These techniques has been developed in Cuba for different X-ray sets.
In this article we describe the suitable working conditions for 32 agricultural and forestry species. We also explained the
main damages to seeds and their consequences for germination. If affected by insects, it could reduce the storage ability
of grains. 相似文献
20.
The free, bound, and strongly bound lipids of the crushed seeds, pulp, husks, and meal have been characterized. It has been shown that the bound and strongly-bound lipids differ from the free lipids by a higher level of saturated acids. The acid numbers of the bound lipids are 5–6 times higher than those of the free lipids.Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 66–68, January–February, 1989. 相似文献