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51.
Predissociation spectra of the H5O2+.Ar(1,2) cluster ions are reported in the 1000-1900 cm(-1) region. The weakly bound argon atoms enable investigation of the complex in a linear action mode, and the resulting spectra are much simpler than those reported previously in this region [Asmis et al., Science 299, 1375 (2003) and Fridgen et al., J. Phys. Chem. A 108, 9008 (2004)], which were obtained using infrared multiphoton dissociation of the bare complex. The observed spectrum consists of two relatively narrow bands at 1080 and 1770 cm(-1) that are likely due to excitation of the shared proton and intramolecular bending vibrations of the two water molecules, respectively. The narrow linewidths and relatively small (60 cm(-1)) perturbation introduced by the addition of a second argon atom indicate that the basic "zundel" character of the H5O2+ ion survives upon complexation. 相似文献
52.
Jeffrey C. Evans Simon K. Jackson Christopher C. Rowlands Martin D. Barratt 《Tetrahedron》1985,41(22):5191-5194
Under acid conditions aqueous solutions of chloramine-T form nitrogen-centred radicals via loss of the chlorine atom. The nitrogen radicals produced have been studied by ESR spectroscopy using the spintrapping method. Adducts of the spin trap phenyl-t-butyl nitrone are oxidized by chloramine-T in acid media to give a paramagnetic product in which the unpaired electron interacts with two inequivalent nitrogen atoms. The spin trap 5,5-dimethyl-2-pyrrolidine-1 -oxide is oxidized rapidly to 5,5-dimethyl-2-pyrrolidone-1-oxyl by chloramine-T under acid onditions. The water soluble trap α-4-pyridyl-1-oxide-N-t-butyl nitrone forms a stable nitroxide adduct with a nitrogen radical of chloramine-T in acid solution. Identical results were obtained with chloramine-B (sodium salt of N-chlorobenzene sulfonamide), indicating the involvement of the N-chloramine group in radical formation. 相似文献
53.
A synthetically useful protocol has been developed for the preparation of highly functionalized N-alkenyl-benzimidazol-2-ones. Reaction of commercially available o-phenylenediamines with variously substituted cyclic ketones provides spiro-benzimidazolines. Treatment of these spiro-benzimidazolines with triphosgene in the presence of potassium carbonate results in rapid rearrangement and formation of N-alkenyl-benzimidazol-2-ones in modest to excellent yield for the two-step sequence. Extension of this methodology toward the preparation of a μ opiate receptor antagonist and droperidol, a potent antiemetic and antipsychotic agent, currently a marketed pharmaceutical is also described. Upon treatment of spiro-benzimidazolines with triphosgene in the presence of sodium triacetoxyborohydride, N-alkyl-benzimidazol-2-ones were formed. 相似文献
54.
Jeffrey I. Zink 《Chemical physics letters》1975,32(2):236-237
The triboluminescence of aniline hydrochloride is the 3Πu → 3Πg fluorescence of adsorbed molecular nitrogen, a new origin for the triboluminescence of aromatic crystals. The lower limit of the triboexcitation energy which can be obtained from organic crystals is 89 kK. 相似文献
55.
Thermolysis of the enyne-carbodiimides 7 having the central carbon-carbon double bond incorporated as part of the cyclopentene ring favors the formation of the corresponding N,4-didehydro-2-(phenylamino)pyridine intermediates, either as the sigma,pi-biradicals 8 or as the zwitterions 8', for subsequent synthetic elaborations. By placing appropriate substituents at the acetylenic terminus, a variety of the intramolecular decay routes are available for the initially formed sigma,pi-biradicals/zwitterions, leading to the 5,6-dihydrobenzo[c][1,8]naphthyridine 21, the 1,2,3,4-tetrahydro[1,8]naphthyridine 24 and related compounds 25 and 26, the 5,6-dihydrobenz[f]isoquinoline 28, and the benzofuro[3,2-c]pyridine 30. Surprisingly, the use of the dimethylamino group of the 2-(dimethylamino)phenyl substituent to capture the carbocationic center in the zwitterion 8e' furnished the 5H-pyrido[4,3-b]indole 32 in only 14% yield. The majority of the products were the 1H-pyrrolo[2,3-b]quinolines 34 and 35, isolated in 48 and 7% yields, respectively. However, it was possible to redirect the reaction toward 32 by conducting thermolysis of the enyne-carbodiimide 7e in the presence of 5 equiv of dimethylphenylsilyl chloride. Under this reaction condition, the 2-pyridone imine 37 was isolated in 86% yield, which on exposure to silica gel was converted to 32 in essentially quantitative yield. Thermolysis of the enyne-carbodiimide 42 having a methoxymethyl substituent at the acetylenic terminus led to the formation of 46' as a pyridine analogue of ortho-quinone methide imine. An intramolecular hetero-Diels-Alder reaction of 46' then furnished the tetrahydro[1,8]naphthyridino[2,1-c][1,4]benzoxazine 47. 相似文献
56.
Sequence-specific phenylacetylene oligomers consisting of functionalized monomers (hexyl benzoate, hexyl phenyl ether, benzonitrile, and tert-butylphenyl) are synthesized in gram quantities using solid-phase methods. Growing oligomers are attached to a divinylbenzene cross-linked polystyrene support by the 1-aryl-3-propyl-3-(benzyl-supported) triazene moiety. This linkage is obtained by reaction of arenediazonium tetrafluoroborate salts with a n-propylamino-modified Merrifield resin. Condensation strategies are described, producing oligomers with higher yields and simplified procedures compared to solution-phase methods. Terminal acetylene is protected with a trimethylsilyl group. After deprotection of the resin-bound terminal acetylene, an aryl iodide monomer or an aryl iodide-terminated oligomer is coupled to the supported oligomer using a palladium(0) catalyst. The cycle can be repeated to produce sequence-specific oligomers of varying length and functionality. The resulting oligomers are liberated from the polymer support by cleavage of the 1-aryl-3-propyl-3-(benzyl-supported) triazene group by reaction with iodomethane producing an aryl iodide. 相似文献
57.
Zhang J Bilic A Reimers JR Hush NS Ulstrup J 《The journal of physical chemistry. B》2005,109(32):15355-15367
The structural organization, catalytic function, and electronic properties of cysteamine monolayers on Au(111) have been addressed comprehensively by voltammetry, in situ scanning tunneling microscopy (STM) in anaerobic environment, and a priori molecular dynamics (MD) simulation and STM image simulation. Two sets of voltammetric signals are observed. One peak at -(0.65-0.70) V (SCE) is caused by reductive desorption of cysteamine. The other signal, at -(0.25-0.40) V consists of a peak doublet. The pH dependence of the latter suggests that the origin is catalytic dihydrogen evolution. The doublet feature is indicative of two distinct cysteamine configurations. Cysteamine monolayer formation from initial nucleation to a highly ordered phase has been successfully observed in real time using oxygen-free in situ STM. Random cellular patterns, disordered adlayer formation accompanied by high step edge mobility, and ultimately a highly ordered (square root 3 x 4) R30 degrees lattice are observed sequentially. Pits are formed due to enclosure of the mobile edges during the adsorption process. In the highly ordered cysteamine layer, each unit has two spots with apparent 0.6 A height difference in STM images. The coverage 5.7 +/- 0.1 x 10(-10) mol cm(-2) determined by voltammetry supports that the spots represent two individual cysteamine molecules. A priori MD and density functional simulations hold other clues to the image interpretation and indicate that the NH(3)(+) groups dominate the tunneling contrast. A wide range of interface structures, showing variations in the sulfur binding site and orientation, gauche and trans conformers, and especially hydrogen-bonding interactions, are examined, from which it is concluded that the adsorbate structure is controlled by interactions with the solvent rather than with the substrate. 相似文献
58.
Polyacrylamide gel electrophoresis was used to resolve as many as three protein components from incubation mixtures containing the inhibitor, 5-fluoro-2′-deoxyuridylate, the cofactor, 5,10-methylene tetrahydrofolate, and thymidylate synthetase. In a series of mixtures containing excess 5,10-methylenetetrahydrofolate and constant levels of thymidylate synthetase, the relative amounts of the protein components were shown to be dependent on the concentration of the inhibitor. Evidence is presented which suggests that the three protein components correspond to (1) native enzyme, (2) an inhibitor-cofactor-enzyme complex in a 1:1:1 molar ratio, and (3) an inhibitorcofactorenzyme complex in a 2:2:1 molar ratio, respectively. Ternary complexes of thymidylate synthetase are stable to gel filtration and are shown to undergo a relatively slow rate of breakdown on storage at 25 °C. 相似文献
59.
[reaction: see text] An effective strategy has been developed for the rapid and efficient one-pot synthesis of 2-aryl-5-substituted-2,3-dihydrobenzofurans from readily available o-nitrotoluenes and aromatic aldehydes. This strategy allows access to a structurally diverse array of products for further manipulation. 相似文献
60.
Plieger PG Ehler DS Duran BL Taylor TP John KD Keizer TS McCleskey TM Burrell AK Kampf JW Haase T Rasmussen PG Karr J 《Inorganic chemistry》2005,44(16):5761-5769
The ligand 4,5-dicarboxyimidazole (H(2)DCI) and its methyl derivative 1-methyl-4,5-dicarboxyimidazole (H(2)MDCI) have been shown to bind to Be(II) forming a zwitterionic species that has been structurally characterized. A new dicarboxyimidazole-based polymer has been prepared and its Be-binding properties have been studied using NMR ((1)H and (9)Be) and fluorescence spectroscopy; it represents a rare example of beryllium binding to a polymer. Models of the mononuclear and polymeric Be(II)-binding sites have been studied using density functional theory (DFT), and the (9)Be NMR chemical shifts of these model materials have been calculated for the purpose of direct comparison to experimentally observed values. Differences in the binding modes of the mononuclear and polymeric species are discussed. 相似文献