Triple Carbon Research Articles

Gold-catalyzed oxidative cleavage of aryl-substituted alkynyl ethers using molecular oxygen. Simultaneous degradation of C–H and single and triple carbon–carbon bonds under ambient conditions

We report the gold-catalyzed oxidative cleavage of aryl-substituted alkynyl ethers using molecular oxygen under ambient conditions; the transformation involves a remarkable cleavage of C-H, C-C and C[triple bond, length as m-dash]C bonds simultaneously.

Coupled cluster study of the phenyl-acetylide anion

Using coupled cluster theory with singles and doubles substitutions (CCSD) we have characterized the ground-state geometry and electronic structure of the phenyl acetylide anion ( 1) which has been recently isolated and characterized by NMR spectroscopy [Y. Tanaka et al., Chem. Asian. J. 1 (2006) 581]. Calculations indicate the bond in the acetylide moiety being an elongated triple carbon carbon bond which becomes strengthened upon interaction with the Li + ion. Fluorine substitution stabilizes the carbanion, as testified by the increase in the HOMO–LUMO energy gap. Minor structural problems encountered with the DFT-optimized geometries are also discussed.

Formation of unprecedented actinide triple bond carbon in uranium methylidyne molecules.

Chemistry of the actinide elements represents a challenging yet vital scientific frontier. Development of actinide chemistry requires fundamental understanding of the relative roles of actinide valence-region orbitals and the nature of their chemical bonding. We report here an experimental and theoretical investigation of the uranium methylidyne molecules X(3)U CH (X = F, Cl, Br), F(2)ClU CH, and F(3)U CF formed through reactions of laser-ablated uranium atoms and trihalomethanes or carbon tetrafluoride in excess argon. By using matrix infrared spectroscopy and relativistic quantum chemistry calculations, we have shown that these actinide complexes possess relatively strong U C triple bonds between the U 6d-5f hybrid orbitals and carbon 2s-2p orbitals. Electron-withdrawing ligands are critical in stabilizing the U(VI) oxidation state and sustaining the formation of uranium multiple bonds. These unique U C-bearing molecules are examples of the long-sought actinide-alkylidynes. This discovery opens the door to the rational synthesis of triple-bonded actinide carbon compounds.

Synthesis of binary and triple carbon nanotubes over Ni/Cu/Al 2O 3 catalyst by chemical vapor deposition

Novel binary and triple carbon nanotubes (CNTs) with one common catalytic particle encapsulated have been synthesized using Ni/Cu/Al 2O 3 catalyst, which was produced by a sol–gel method. But when using Ni/Al 2O 3 as catalyst, a mass of common CNTs, that is, one CNT with one catalytic particle encapsulated, was obtained. The results showed that copper-element doping to the Ni/Al 2O 3 catalyst played a key role in the synthesis of CNTs, signifying a novel approach to modify the Ni/Al 2O 3 catalyst. Based on the transmission electron microscopy observations, a simple growth mechanism was developed to describe the growth of the binary or triple CNTs, which could be well explained by a diffusion segregation process.

Carbon nanoparticle stabilised liquid|liquid micro-interfaces for electrochemically driven ion-transfer processes

Stabilised liquid|liquid interfaces between an organic 4-(3-phenylpropyl)-pyridine (PPP) phase and an aqueous electrolyte phase are obtained in the presence of suitable nanoparticles. The use of nanoparticulate stabilisers (ca. 30 nm diameter laponite or 9–18 nm diameter carbon) in “Pickering” emulsion systems allows stable organic microdroplets to be formed and these are readily deposited onto conventional tin-doped indium oxide (ITO) electrodes. In contrast to the electrically insulating laponite nanoparticles, conducting carbon nanoparticles are shown to effectively catalyse the simultaneous electron transfer and ion transfer process at triple phase boundary junctions. Anion transfer processes between the aqueous and organic phase are driven electrochemically at the extensive triple phase junction carbon nanoparticle|4-(3-phenylpropyl)-pyridine|aqueous electrolyte. The organic phase consists of a redox active reagent 5,10,15,20-tetraphenyl-21H,23H-porphinato manganese(III) (MnTPP +), 5,10,15,20-tetraphenyl-21H,23H-porphinato iron(III) (FeTPP +), or proto-porphyrinato-IX iron(III) (hemin) dissolved in 4-(3-phenylpropyl)-pyridine (PPP). The composition of the aqueous electrolyte phase determines the reversible potential for the Nernstian anion transfer process. The methodology is shown to be versatile and, in future, could be applied more generally in liquid|liquid electroanalysis.

Sludgy urine in rabbits

normally contains triple phosphate and calcium carbonate crystals.The rabbit has an unusual calcium metabolism.The uptake and excretion of calcium is not finely controlled by homeostatic mechanisms as in other mammals, rather that plasma calcium is directly linked to dietary calcium, and any excess is excreted in the urine. Excess calcium carbonate in the urine does predispose to bladder ‘sand’ (sludge) and urolithiasis.

Quantification of the Push−Pull Effect in Tolanes and a Revaluation of the Factors Affecting the13C Chemical Shifts of the Carbon Atoms of the C⋮C Triple Bond

Variously substituted tolanes were employed to show that the push-pull effect is also active in CC triple bonds by the successful correlation of the occupation quotient pi/pi of the pi orbital in resonance with the substituted phenyl moieties of tolanes versus the bond length of the CC triple bond. In addition, the influences of the ortho phenyl ring substituents on the 13C chemical shifts of the triple bond carbon atoms, which were estimated by Rubin et al.(4) to be "inapplicable for describing triple bond polarization", were re-evaluated, leading to the conclusion that, while anisotropic effects of ortho substituents are negligible, the steric ortho-substituent effects do in fact dominate the deviations obtained. A detailed theoretical NBO/NCS study has been employed to illuminate the facts of this case.

Structural characterisation of crystalline carbon nitride thin films synthesised by electrolysis of urea–methanol solution

Polycrystalline carbon nitride thin films were deposited on Si(400) and ITO coated glass substrates by electrolysis of methanol–urea solution under high voltage, at atmospheric pressure and at temperatures below 350 K. Fourier transform infrared spectroscopy (FTIR) measurements of the films deposited on Si suggested the existence of single, double and triple carbon–nitrogen bonds in the films. A maximum N/C atomic ratio of 0·81 was achieved in the films as measured by C/H/N analysis. X-ray diffraction spectra of the films grown with different urea concentrations showed various peaks for different d values, which could be assigned to different crystalline carbon nitride phases. Selected area electron diffraction patterns measured by transmission electron microscopy (TEM) showed a number of concentric sharp rings, corresponding to various planes of theoretically predicted β-C3N4 phase. Scanning electron microscopy (SEM) images of the films indicated the existence of grains, the number density and size of which were dependent on the solute concentration. Optical transmission measurements of the films on ITO coated glass substrates revealed a band gap value of around 2·87 eV for direct transition. The hardness of the films on Si substrates was as high as 28 GPa.

Electrophilic Activation and Cycloisomerization of Enynes: A New Route to Functional Cyclopropanes

AbstractFor Abstract see ChemInform Abstract in Full Text.

Photocatalytic degradation of acetylene over various titanium dioxide-based photocatalysts

The photodegradation of acetylene (C2H2) was investigated over various powders or supported titanium dioxide (TiO2) photocatalysts in air into static conditions. It was found that UV-irradiated TiO2 is effective in order to lead to the complete mineralization of the pollutant containing a triple carboncarbon bonding without deactivating. No organic intermediates were detected in the gas phase, implying that oxidation mechanisms take place in the adsorbed phase. The efficiency of P25-Degussa and PC500-Millennium photocatalysts were compared; the mixed anatase/rutile P25-Degussa is reported as the most efficient photocatalytical material in our conditions. The topology of the photocatalyst support is reported as a significant parameter in TiO2 efficiency. Fibre-deposited photocatalysts lead to the highest activity, and the chemical nature of the fibre did not influence the photodegradation. The influence of TiO2 amonut, silica binder and adsorbing additives such as zeolite, and activated carbon coupled with TiO2 photocatalyst were investigated.

Energetics, electronic structures and geometries of didehydroazines

When calibrated against the available experimental data for didehydrobenzenes, RB3LYP/cc-pVTZ, QCISD/cc-pVTZ, CCSD(T)/cc-pVTZ, and G3 electronic structure calculations provide reliable predictions of standard enthalpies and singlet—triplet splittings in all possible isomers of didehydroazines that (with a possible exception of 2,6-didehydropyridine) possess singlet ground states. Singlet didehydroazines with larger numbers of nitrogen atoms turn out to be more prone to ring opening, as indicated by the fact that out of the 6, 11, 6 and 3 possible didehydropyridines, didehydrodiazines, didehydrotriazines, and didehydrotetrazines, respectively, 5, 7, 2 and none are actually found. Immediate proximity of the nitrogen atom to the formally triple carbon—carbon bond confers decreased thermodynamic stabilities and smaller singlet—triplet splittings on the species of the 1,2-didehydro type. Some of the aza analogues of singlet 1,3-didehydrobenzene are as stable as their 1,2-didehydro counterparts. The only existing aza analogue of singlet 1,4-didehydrobenzene is 2,5-didehydropyrazine, which is particularly stable and possesses a large singlet—triplet splitting, making it a feasible synthetic target. The present calculations indicate that the experimental standard enthalpies of formation of pyrimidine and pyrazine are in error.

「化学療法処方せん兼指示票」の導入とアンケート調査による評価

We manage most of medical slips by writing down information by hand, because our hospital does not have an ordering system. For instructions on cancer chemotherapy, we suggested that posting instructions of the medical card in the injection prescription by each medicine bottle could lead to the possibility of some medication errors on account of 1) a risk for posting errors and 2) difficulty of general inspection. To improve the present situation, we established a system called “Prescription-Instruction Sheet of Chemotherapy” and have utilized it since July, 2001. It is made up of triple carbon paper A 4 size which is printed on the whole protocol of chemotherapy. It shows three functions, namely a prescription, a copy of the ward and an instruction sheet for nurses, as soon as a doctor fills in the blanks on the sheet.One year after introducing this system, we investigated a questionnaire to ask about the usefulness of this sheet to the medical stuff. The results were highly satisfactory, because most opinions mentioned that the posting of medical cards become unnecessary and the schedule is easy to understand at first sight. Nurses had some recommendations to improve this sheet. On the other hand, the number of incidents and accident reports decreased after introducing this system to the department of nursing.We conclude that this system helped to improve the risk management owing to the establishment of this new system.

Properties of carbon nitride (CNx) films deposited by a high-density plasma ion plating method

Carbon nitride (CNx) films have been deposited in a hollow cathode arc (HCA) ion plating system with a high-density plasma, including a high degree of dissociation of nitrogen. Optical emission spectra (OES) were obtained to characterize the Ar/N2 plasma during the deposition of carbon nitride films. The species identified include C2, N2, N2+ and CN. The variations of the OES spectra with pressure are correlated with film growth behavior. The films deposited on Si (100) substrates were characterized by FTIR, Raman, and SEM. Single, double and triple carbon nitride bonds were detected in the FTIR spectra, and the relative intensities of the associated bands were dependent on the pressure and the substrate bias. Raman spectra showed an increase of the sp2 carbon phase in carbon nitride films with the increase of pressure and the substrate bias. The internal stresses were measured by substrate bending using the Stoney equation. The internal stress of carbon nitride films was observed to depend mainly on the substrate bias.

Perioperative shivering: physiology and pharmacology.

IN homeothermic species, a thermoregulatory system coordinates defenses against cold and heat to maintain internal body temperature within a narrow range, thus optimizing normal physiologic and metabolic function. The combination of anesthetic-induced thermoregulatory impairment and exposure to a cool environment makes most unwarmed surgical patients hypothermic. Although shivering is but one consequence of perioperative hypothermia, and rarely the most serious, it occurs frequently (i.e., 40–60% after volatile anesthetics), and it remains poorly understood. While coldinduced thermoregulatory shivering remains an obvious etiology, the phenomenon has also been attributed to numerous other causes. Our first goal is to review the organization of the thermoregulatory system, and particularly the physiology of postanesthetic shivering. We then discuss the pharmacology of thermoregulation and review the putative mechanisms and sites of action of various antishivering drugs.

Specific Features of the Composition of Solid Phases in the Na+K+Ca2+∥CO 3 2- OH--H2O System

The composition of solid phases in the Na+K+Ca2+∥CO32-OH--H2O system at 95°C was studied. Triple carbonates of alkali metals and calcium, different from the known synthetic and natural compounds, were found in the system.

Linking climate change research with food security and poverty reduction in the tropics

Climate change is a reality and will affect the poor in developing countries in many ways. The effectiveness of global change research could be substantially improved by linking International Geosphere-Biosphere Programme (IGBP) study with Consultative Group on International Agricultural Research (CGIAR) centres based in the tropics. These centres are carrying interdisciplinary research and development on how to achieve food security and reduce rural poverty through the innovative management of natural resources. A CGIAR intercentre working group on climate change (ICWG-CC) identified joint opportunities that take advantage of the comparative advantages of both institutions. CGIAR centres will focus on adaptation and mitigation research in developing countries. A natural resource management research approach is suggested, which consists of six steps: (1) identifying and quantifying the extent of food insecurity, rural poverty and resource degradation; (2) conducting technological and policy research on economic and environmental functions; (3) optimising the trade-offs between global environmental benefits and private farmer benefits; (4) extrapolating and disseminating results, including research on policy implementation; (5) assessing impact and (6) providing feedback. Two examples of current CGIAR research illustrate this approach. Agroforestry alternatives to slash and burn (ASB) agriculture at tropical forest margins were identified and the trade-offs between carbon sequestration and farmer profitability provided options to policy makers. Land tenure problems were resolved with participatory policy research. Agroforestry practices sequester an additional 57 Mg C per ha, three times that of croplands or grasslands are able to do. Soil nutrient capital is being replenished in subhumid tropical Africa through improved leguminous tree fallows, rock phosphate and biomass transfers of Tithonia diversifolia, helping farmers to attain food security. Afterwards, when farmers shift to high-value tree or vegetable crop production, poverty is reduced. The transformation of low productivity croplands to sequential agroforestry is estimated to triple system carbon stocks in 20 years.

Synthesis of cyclopentenones and butenolides by reaction of the lithium salt of P,P-diphenyl-P-(alkyl)(N-phenyl)phosphazenes with electrophilic double and triple bonds

Lithium P,P-diphenyl-P-(alkyl)(N-phenyl)phosphazenes act as bidentate reagents towards electrophilic olefins and acetylenes. The reactions with dimethyl acetylenedicarboxylate (DMAD) and dimethyl maleate afford cyclopentenones, while with methyl benzoylpropiolate the products obtained are butenolides with a quaternary carbon atom in position 5 of the heterocycle. The use of less activated substrates (methyl phenylpropiolate, methyl cinnamate, and dimethyl oxalate) allowed the isolation of C-acylated aminoylide or phosphazene derivatives. A reaction mechanism is proposed based on a tandem process involving the regioselective C-acylation of the carbon α to the phosphorus, followed by a cyclisation process promoted by the intramolecular Michael addition of the nitrogen of the PN linkage to an electrophilic double or triple carbon–carbon bond.

High accuracy studies on the ground state and transition state of SiC 2

The long controversial isomers of the interstellar molecule SiC 2, i.e. the cyclic C 2v isomer A, the linear C ∞v isomer B, together with the newly discussed D ∞h isomer C have been studied to reveal the nature of the stable structure. The spin-restricted MP2, QCISD, CCSD(T), the Gaussian-2 method G2MP2, the density-functional theory (DFT) method BLYP, and the hybrid Hartree–Fock–DFT methods Becke3LYP and BhandhLYP were employed with both 6-31G* and 6-311G* basis sets. The DFT methods fail to reproduce some experimental conclusions except for BhandhLYP. Based on the accurate calculation of MP2, QCISD, CCSD(T) and G2MP2, the experimentally detected isomer A is indeed more energetically favorable than the linear C ∞v isomer B. But their energy difference decreases with the increase of the correlation level and the size of the basis set. The predicted assignment of the electronic absorption spectrum of A is B 2←A 1, which is identical to the experimental outcome. The predicted vibrational spectra of A are also in excellent agreement with experimental data. It has been revealed that the linear isomer is not a true stationary point by the QCISD and CCSD(T) methods. It was suggested that the triangular form be best described by the half-to-half hybrid bonding of the ionic and covalent characters between Si and C 2 fragments with about 0.56 e of the charge transfer at the 6-311G* level. After considering the bond-length of the C 2 fragment, it is closer to the CC in cyclopropene rather than the triple carbon bond suggested previously. The electronic energy of isomer C is too high to be stable compared with the other two states, which was interpreted by means of the orbital correlation diagram. Investigation on the transition state TS for the isomerization between A and B reveals that isomer B will automatically transform to the more stable C 2v form, which shows that B is dynamically unstable. As a conclusion, the C 2v isomer is not only thermodynamically but also dynamically stable, which explains the fact that B has not been experimentally detected.

Photoelectron spectra of vinyl- and 1-alkynylgermanes and stannanes

Primary vinylic and acetylenic germanes and stannanes, synthesized by a chemoselective reduction of the corresponding trichloro derivatives, were investigated by ab initio quantum chemical methods and photoelectron spectroscopy. In particular, the PE spectra display very well-resolved bands which show the increasing destabilizing effect of 14 group heteroatom α-substitution of double or triple carbon–carbon bonds.

Production and characterisation of carbon nitride thin films produced by a graphite hollow cathode system

Carbon nitride thin films have been prepared by plasma enhanced chemical vapour deposition of CH 4 and N 2 gas mixtures, by chemical transport from a hollow graphite cathode. The deposits prepared on pieces of single crystal silicon substrates were characterised using FTIR, Raman, SEM, EDX, SIMS, X-ray and electron diffraction. Single, double and triple carbon nitrogen bonds were detected in the FTIR spectra; the relative intensities of the associated bands being a function of the plasma power and substrate bias. Elemental analysis of the deposit showed that the nitrogen content was ∼57 at%. A polycrystalline deposit identified as hexagonal β-C 3N 4 was obtained at low substrate temperatures. The deposit was found to grow preferentially on scratch defects on the silicon substrate surface and was stable upon annealing under vacuum up to 700°C.