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101.
The product from the fluorination of pyridine by KCoF4 at ca. 220° contains eleven fluoropyridines, two fluoro-2-azahex-enes, three azahexa- dienes, and two fluoro-N-methylpyrrolidines, besides an azacyclohexa-1,3- diene. Four products were isolated from a fluorination of pyridine by CoF3 at ca. 150°, a 2-azahexene, two N-methylpyrrolidines, and 4H-nona- fluoropiperidine. 相似文献
102.
Prediction of the glass transition temperature for compatible polymer blends of varying compositions
Compatible polymer blends have been found to have widespread commercial applications. The simplest criterion for judging polymer—polymer miscibility in the solid state is the glass transition temperature (Tg), which can vary widely according to blend composition for a compatible system.Recently, an equation which predicts the Tg of intimate mixtures of compatible polymers has been derived, based on classical thermodynamics. Only a knowledge of the Tg and heat capacity increment (ΔCp) of each pure component is required to predict the Tg at any composition.In this paper, the validity of this entropy-based relationship is investigated for a variety of commercial compatible polymer blends, including some based on poly(vinyl chloride), polystyrene, and poly(2,6-dimethyl-,4-phenylene oxide). The Tg and ΔCp of each pure component are measured with a Perkin-Elmer DSC-2 differential scanning calorimeter, are predicted glass transition temperatures are compared with those observed experimentally. 相似文献
103.
Paul Vouros 《Journal of heterocyclic chemistry》1975,12(1):21-25
The electron impact mass spectra of several substituted thiirene and thiophene oxides and dioxides have been investigated using both low and high resolution mass spectrometry. The predominant fragmentation process in the spectra of the thiirene compounds is the elimination of the hetero (SO or SO2) function and formation of a substituted acetylene ion. The 5-membered ring thiophene dioxides exhibit mainly elimination of SO rather than SO2. Plausible mechanisms leading to the formation of the principal ions are proposed on the basis of metastable transitions. 相似文献
104.
Irradiation of in methanoi with λ 254 nm yields and as the main primary products which result from the excited singlet state hy initial cyclopropane bond homolysis, but no primary photosolvolysis products. 相似文献
105.
Michael Beyer Ramin Ghaffari-Tabrizi Michael Jung Paul Margaretha 《Helvetica chimica acta》1984,67(6):1535-1539
On acetone-sensitized irradiation the title compounds 3a–c are converted to 2-allyl-3-hydroxy-1H-pyrrole-2-carboxylates 4 in reasonable yields. 相似文献
106.
Wormer PE 《The Journal of chemical physics》2005,122(18):184301
A short self-contained derivation is given for the second virial coefficient B2(T) of a gas consisting of identical interacting asymmetric rigid rotors. The resulting expression is correct through variant Planck's over h2. First, the canonical partition function is derived by means of an variant Planck's over h expansion of exp[-H/(k(B)T)] due to Friedmann [Adv. Chem. Phys. 4, 225 (1962)]. The present work applies angular momentum operators and known facts from angular momentum theory. It is considerably more accessible than Friedmann's exposition, which is not based on angular momentum operators, but instead on explicit derivatives with respect to Euler angles. The partition function obtained from the variant Planck's over h expansion is applied to the derivation of an expression for B2(T) that is identical in appearance to the expression for symmetric rotors of T Pack [J. Chem. Phys. 78, 7217 (1983)]. The final equation in this work is valid for rigid rotors of any symmetry. 相似文献
107.
108.
Hans-Rudolf Waespe Heinz Heimgartner Hans Schmid Hans-Jürgen Hansen Henning Paul Hanns Fischer 《Helvetica chimica acta》1978,61(1):401-429
The photochemical reactions of different allyl aryl ethers (Scheme 3) were investigated in hydrocarbons (Chap. 3.1) and in alcoholic solvents (Chap. 3.2). The composition of the photoproducts depended very much on the nature of the solvent. Irradiation (3–95 h) of different methyl substituted allyl aryl ethers ( 1, 3, 5, 7 and 11 ) with a low pressure mercury lamp (λEmiss. = 254 nm; 6 or 15 Watt) under argon (quartz vessel) resulted in the formation of 2-, 3– and 4-substituted phenols, dienones and products of consecutive reactions (Tables 1–4 and 6). The results suggested that all products were formed by homolytic cleavage of the C? O bond in the singlet state of the ethers to intermediate radical-geminates (Scheme 5) followed by radical recombination of the two fragments. No products were formed by concerted processes (Table 5, Schemes 5 and 6). Upon irradiation of allyl aryl ethers lacking alkyl substituents at position 4 ( 1 and 5 ) in protic solvents, mainly 2- and 4-allylated phenols were obtained (Tables 1 and 4); 3-allylated phenols were formed only in small amounts (0.02%). However, in aromatic hydrocarbons or cyclohexane 3-allylated phenols were obtained from 1 , 5 and 11 in significant amounts (3–11%; Tables 1, 4 and 6). E.g., upon irradiation of allyl-2,6-dimethyl-2,4-cyclohexadien-1-one ( 6 ) besides 3- and 4-allyl-2, 6-dimethyl-phenol ( 23 and 24 ). Irradiation of 5 in methanol afforded 23 and 6 only in traces, whereas 24 was the main product. 相似文献
109.
The focal point of our discussion is the examination of truncated basis sets used in obtaining an accurate first principles clculation of the effective valence shell Hamiltonian by the canonical transformation-cluster expansion approasch. Subsequent diagonalization of this effecitve valence shell hamiltonian yields the valence shell transition energies. A detailed analysis of numerical results obtained using a number of different basis sets of hydrogen-like orbitals together with rigorous symmetry arguments celarly demonstrates the special role played by d orbitals in computing the 3P → 1D transition energy in carbon. The failure of early attempts to calculate the effective Hamiltonian for ethylene from first principles is examined in the light of recent ab initio calculations on ethylene involving d orbitals and the computations reported in this paper. We conclude that accurate calculations of the effective valence shell Hamiltonian for molecules must consider d orbitals in the excited orbital basis set. 相似文献
110.
The amount of chemiluminescence (CL) or light that is emitted from human polymorphonuclear leukocytes (PMN) during phagocytosis or activation by soluble stimuli is dependent on the emission of photons from the oxidation of particulate or bystander molecules. Because the compounds luminol and lucigenin yield photons with high quantum efficiency these agents have been introduced to sensitively assess PMN-CL. Since there is limited information about the pathways involved in the chemiluminescence of these compounds, we investigated the role of both myeloperoxidase (MPO) and superoxide anion (· O2?) in luminol-and lucigenin-PMN-CL. We compared the CL between normal and MPO- deficient PMN using zymosan for phagocytosis and N-formylmethionyleucylphenylalanine (FMLP) as a soluble stimulus. Our data demonstrated that luminol-CL was dependent on the presence of MPO and independent of · O2? generation during phagocytosis but independent of MPO during FMLP activation. In contrast lucigenin-CL was independent of MPO during both phagocytosis and FMLP activation and appeared to reflect · O2? production. Consequently, dependent on the type of activation, it appears that luminol- and lucigenin-CL are generated via different oxidative pathways and may serve as potentially useful tools to differentiate the redox activity of phagocytic cells. 相似文献