Elimination Of Carbon Monoxide Research Articles

Iridium-Catalyzed Annulative Coupling of 2-Arylbenzoyl Chlorides with Alkynes: Selective Formation of Phenanthrene Derivatives

2-Arylbenzoyl chlorides undergo annulative coupling with internal alkynes in the presence of a catalyst system of [IrCl(cod)]2/P(t-Bu)3 to selectively afford the corresponding phenanthrene derivatives accompanied by elimination of carbon monoxide and hydrogen chloride. The reaction occurs without addition of any external base. Deuterium-labeling experiments using 2-(d5-phenyl)benzoyl chloride suggest that the rate-determining step does not involve the C2'-H bond cleavage. Formation of a [(t-Bu)3PH][(biphenyl-2,2'-diyl)Ir(CO)Cl2] complex dimer, of which the structure was determined by single-crystal X-ray analysis, from a stoichiometric reaction at 60 °C without addition of alkyne also supports the facile C-H cleavage.

Nickel-catalyzed Decarbonylative and Decarboxylative Cycloaddition of Isatoic Anhydrides with Alkynes

Abstract We have developed a nickel-catalyzed cycloaddition of isatoic anhydrides with alkynes to afford 2,3-disubstituted indoles. The reaction proceeds via the elimination of carbon monoxide and carbon dioxide and the insertion of alkynes.

Increased Carbon Monoxide Clearance during Exercise in Humans

Hyperventilation increases the clearance of carbon monoxide (CO) from blood; thus, we hypothesized that CO elimination would be enhanced with exercise. Accordingly, this study examined the effect of exercise on the half-life of carboxyhemolobin elimination. Six healthy subjects (three males and three females) with mean ± SD ages of 23 ± 4 yr were exposed to CO sufficient to raise blood carboxyhemolobin concentration to 10-14% on five separate days. The half-life for CO elimination was measured breathing room air at rest and during exercise at three intensities. Comparisons showed that the half-life decreased with exercise from that during rest in all subjects. The half-life was also measured during 100% oxygen breathing at the lowest exercise intensity of 63 ± 15 W and found to be the least of all measured (23 ± 4 min). 1) Exercise increased isocapnic ventilation, thereby decreasing the half-life of CO elimination. 2) The half-life of CO elimination represents a hyperbolic function of ventilation [y = y0 + (a / x)], and so increasing ventilation by exercise reaches a point of diminishing returns. 3) Breathing 100% oxygen during mild exercise is as effective in eliminating CO as treatment with hyperbaric oxygen. 4) Moderate exercise under room air conditions is as effective in eliminating CO as breathing oxygen at rest. Thus, the combination of mild exercise, hyperventilation, and normobaric hyperoxia (100% oxygen inhalation) may be considered the "triple therapy" for CO elimination in some patients.

Product Detection of the CH Radical Reaction with Acetaldehyde

The reaction of the methylidyne radical (CH) with acetaldehyde (CH(3)CHO) is studied at room temperature and at a pressure of 4 Torr (533.3 Pa) using a multiplexed photoionization mass spectrometer coupled to the tunable vacuum ultraviolet synchrotron radiation of the Advanced Light Source at Lawrence Berkeley National Laboratory. The CH radicals are generated by 248 nm multiphoton photolysis of CHBr(3) and react with acetaldehyde in an excess of helium and nitrogen gas flow. Five reaction exit channels are observed corresponding to elimination of methylene (CH(2)), elimination of a formyl radical (HCO), elimination of carbon monoxide (CO), elimination of a methyl radical (CH(3)), and elimination of a hydrogen atom. Analysis of the photoionization yields versus photon energy for the reaction of CH and CD radicals with acetaldehyde and CH radical with partially deuterated acetaldehyde (CD(3)CHO) provides fine details about the reaction mechanism. The CH(2) elimination channel is found to preferentially form the acetyl radical by removal of the aldehydic hydrogen. The insertion of the CH radical into a C-H bond of the methyl group of acetaldehyde is likely to lead to a C(3)H(5)O reaction intermediate that can isomerize by β-hydrogen transfer of the aldehydic hydrogen atom and dissociate to form acrolein + H or ketene + CH(3), which are observed directly. Cycloaddition of the radical onto the carbonyl group is likely to lead to the formation of the observed products, methylketene, methyleneoxirane, and acrolein.

Highly ordered magnetic mesoporous silicas for effective elimination of carbon monoxide

Catalysts based on crystalline nanoparticles of Fe metal supported on mesoporous silica have been developed. The synthetic process involves hydrogen reduction processing for high abundant Fe metal nanoparticles within the mesopores, in which impregnated Fe salt in the inner nanopores of mesoporous silica is thermally treated under hydrogen at 500°C. Detailed characterization was achieved by XRD, XPS, BET, and HR-TEM techniques. The catalytic efficiency was demonstrated as a function of the used amounts and reaction time. The results show that more than 90% of the carbon monoxide was eliminated at room temperature during a period 80min with 0.5g of catalyst.

Carbon monoxide exposure during exercise performance: muscle and cerebral oxygenation

To investigate the effect of carbon monoxide (CO) in the inspired air as anticipated during peak hours of traffic in polluted megalopolises on cerebral, respiratory and leg muscle oxygenation during a constant-power test (CPT). In addition, since O(2) breathing is used to hasten elimination of CO from the blood, we examined the effect of breathing O(2) following exposure to CO on cerebral and muscle oxygenation during a subsequent exercise test under CO conditions. Nine men participated in three trials: (i) 3-h air exposure followed by a control CPT, (ii) 1-h air and 2-h CO (18.9 ppm) exposure succeeded by a CPT under CO conditions (CPT(COA)), and (iii) 2-h CO and 1-h 100% normobaric O(2) exposure followed by a CPT under CO conditions (CPT(COB)). All exercise tests were performed at 85% of peak power output to exhaustion. Oxygenated (Δ[O(2)Hb]), deoxygenated (Δ[HHb]) and total (Δ[tHb]) haemoglobin in cerebral, intercostal and vastus lateralis muscles were monitored with near-infrared spectroscopy throughout the CPTs. Performance time did not vary between trials. However, the vastus lateralis and intercostal Δ[O(2)Hb] and Δ[tHb] were lower in CPT(COA) than in CPT. During the CPT(COB), the intercostal Δ[O(2) Hb] and Δ[tHb] were higher than in the CPT(COA). There were no differences in cerebral oxygenation between the trials. Inspiration of 18.9 ppm CO decreases oxygenation in the vastus lateralis and serratus anterior muscles, but does not affect performance. Breathing normobaric O(2) moderates the CO-induced reductions in muscle oxygenation, mainly in the intercostals, but does not affect endurance.

Thermal decomposition of potassium titanium oxalate

The thermal decomposition of potassium titanium oxalate (PTO) was studied using non-isothermal thermogravimetry at different heating rates under a nitrogen atmosphere. The thermal decomposition of PTO proceeds mainly through five stages forming potassium titanate. The theoretical and experimental mass loss data are in good agreement for all stages of the thermal decomposition of PTO. The third thermal decomposition stage of PTO, the combined elimination of carbon monoxide and carbon dioxide, were subjected to kinetic analyses both by the method of model fitting and by the model free approach, which is based on the isoconversional principle. The model free analyses showed that the combined elimination of carbon monoxide and carbon dioxide and formation of final titanate in the thermal decomposition of PTO proceeds through a single step with an activation energy value of about 315 kJ mol-1.

The effect of pressure on removal of carbon monoxide in biofilter

Solubility of carbon monoxide in water is very important for its biological oxidation or removal process of gaseous pollutants. Present research shows the effect of pressure on solubility of carbon monoxide in liquid phase and its removal process by a biofilter. The results are considered as laboratory research on carbon monoxide elimination. In this method a pressurized trickle-bed biofilter was used to increase pressure in the reactor. The biofilter was filled with Leca-stones and inoculated with microorganisms. When the system’s pressure is increased, the solubility of carbon monoxide will be increased, respectively, and it causes a better reaction of the microorganisms for removing of gaseous pollutants. The efficiency was improved significantly by increasing the pressure in the reactor.

Effect of Particle Size on Non-Isothermal Decomposition of Potassium Titanium Oxalate

Abstract The effect of particle size on the thermal decomposition of potassium titanium oxalate (PTO) has been studied using TG-DTA-DTG techniques in nitrogen atmosphere at different heating rates. The thermal decomposition of PTO undergoes through five stages, finally forming the stable potassium titanate. The theoretical mass loss data agree very well with experimental data for all stages of the thermal decomposition of PTO. The third thermal decomposition stage of PTO, the combined elimination of carbon monoxide and carbon dioxide, were subjected to kinetic analyses by a model free method, which is based on the isoconversional principle. We observed that both the onset and peak temperatures in DTA and DTG and the apparent activation energy are independent of particle size. The kinetic results indicate that the third thermal decomposition stage of PTO, the combined elimination of carbon monoxide and carbon dioxide, undergoes through a single step.

Dual-catalyst aftertreatment of lean-burn engine exhaust

Pd/SZ catalysts prepared by a sol–gel technique were investigated with regards to their NO 2 selective catalytic reduction activity for application in a novel integrated NO-CO-hydrocarbon oxidation and NO x -selective catalytic reduction system for aftertreatment of lean-burn natural gas reciprocating engine exhaust. The dual-catalyst system consists of a mechanical mixture of a non-noble-metal based oxidation catalyst component (Co/ZrO 2) for elimination of carbon monoxide and unburned hydrocarbons and oxidation of NO to NO 2 and a reduction catalyst component (Pd/SZ) for selective catalytic reduction (SCR) of NO 2 with CH 4. The effect of sol–gel preparation parameters on the activity of Pd/SZ was investigated. The zirconium alkoxide concentration was varied between 0.3 M and 1.3 M during preparation of the Pd/SZ series of catalysts while other sol–gel parameters, such as hydrolysis and zirconium-to-sulfur precursor ratios and palladium loadings were kept constant. Pd/SZ prepared with the lowest concentration of alkoxide was mainly composed of metastable tetragonal zirconia while increasing alkoxide concentration resulted in decreased stability of t-ZrO 2 as evidenced by formation of m-ZrO 2 domains. Crystal phase of ZrO 2 was observed to have a significant effect on Pd dispersion. Palladium dispersion increased with increasing concentration of the monoclinic phase. The best performing Pd/SZ catalyst was further tested as the NO x reduction catalyst component for simulated lean exhaust treatment over the dual-catalyst scheme where, N 2 yields in excess of 90% along with significant conversions of CO, CH 4, C 2H 6 and C 3H 8 were achieved at 450 °C. The NO x reduction activity of Pd/SZ was significantly inhibited in the presence of water vapor. The presence of oxidation catalyst in close proximity to the reduction catalyst was shown to act to offset the effect of water vapor. Above 70% N 2 yield was achieved at 450 °C in the presence of 7% water vapor during simulated lean exhaust treatment over the dual-catalyst system.

Unusual Mass Spectrometric Dissociation Pathway of Protonated Isoquinoline-3-Carboxamides Due to Multiple Reversible Water Adduct Formation in the Gas Phase

The study of the collision-induced dissociation behavior of various substituted isoquinoline-3-carboxamides, which are amongst a group of drug candidates for the treatment of anemic disorders (e.g., FG-2216), allowed for the formulation of the general mechanisms underlying the unusual fragmentation behavior of this class of compounds. Characterization was achieved with high-resolution/high accuracy LTQ-Orbitrap tandem mass spectrometry of the protonated precursor ions. Presented data were substantiated by the synthesis and analysis of proposed gas-phase intermediate structures and stable isotope labeled analogues, as well as by density functional theory calculations. Exemplary, CID of protonated N-[(1-chloro-4-hydroxy-7-isopropoxy-isoquinolin-3-yl)carbonyl]glycine gives rise to the isoquinoline-3-carboxy-methyleneamide product ion which nominally eliminates a fragment of 11 u. This was attributed to the loss of methyleneamine (-29 u) and a concomitant spontaneous and reversible water addition (+18 u) to the resulting acylium ion to yield the protonated isoquinoline-3-carboxylic acid. The same water addition pattern is observed after loss of propylene (-42 u). A further nominal loss of 10 u is explained by the elimination of carbon monoxide (-28 u) followed by another water adduct formation (+18 u) to yield the protonated 1-chloro-3,4,7-trihydroxy-isoquinoline. The source of the multiple gas-phase water addition remained unclear. This atypical fragmentation pattern proved to be highly characteristic for all studied and differentially substituted isoquinoline-3-carboxamides, and offers powerful analytical tools for the establishment of a LC/MS(/MS) based screening procedure for model HIF-stabilizers and their potential metabolites in clinical, forensic and sports drug testing.

Synthesis and optical properties of tetrapyrazinoporphyrazine containing phenylene dendron unit as a peripheral substituent

A dendritic shell can create a distinct micro-environment within its core. It also has the advantage of possessing unique photochemical, photophysical, electrochemical, and catalytic properties. Polyphenylene dendrons, which are characterized by their shape-persistent structures and out-of-plane twisted phenyl components, have previously been successfully attached to various functional groups. We have recently developed a convenient method for synthesizing a new type of porphyrazine that contains both flexible (linear) and more rigid (dendritic) groups. The synthesis of this completely aromatic and dendronic structure is unique in that it is based on a [2+4] Diels-Alder cycloaddition of tetraphenylcyclopentadienone to an ethynyl compound, followed by the elimination of carbon monoxide. In this study, tetrapyrazinoporphyrazinato metal and metal-free complexes were prepared by mixing 2,3-dicyano-5-polyphenylpyrazines with magnesium in n-butanol. The synthesized tetrapyrazinoporphyrazines were characterized by UV-visible spectroscopy, MALDI-TOF-MS (matrix-assisted laser desorption/ionization time-of-flight mass) spectrometry, elemental analysis and 1 H NMR spectroscopy.

Carbon monoxide poisoning in a patient with carbon dioxide retention: a therapeutic challenge

We present the case of a 70 year-old man with carbon monoxide poisoning following a house fire. A significant smoking history and likely underlying chronic lung pathology complicated treatment, as due to symptomatic retention of carbon dioxide we were unable to use high-flow oxygen to facilitate the elimination of carbon monoxide. We suggest that patients with risk factors for obstructive lung disease be monitored extremely carefully during treatment for carbon monoxide toxicity.

ChemInform Abstract: Carbon—Carbon Bond Formation Reaction Promoted by Elimination of Carbon Monoxide or Hydrogen and the Related Reactions

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

LC–high-resolution multiple stage spectrometric analysis of diuretic compounds: Unusual mass fragmentation pathways

The analysis of diuretic compounds has become of great concern because of their extensive use both in therapy and in illicit treatments (such as masking agents in sport doping and drug abuse). The variety of chemical structures of this class of drugs encouraged the development of new methods and techniques of analysis, especially as regards to acidic compounds. LC/MS has so grown to be the reference technique for this kind of analysis in forensic and anti-doping confirmation purposes. Multiple stage MS permits identification of single drugs with high selectivity, but some unexpected pathways could weaken the entire process. In this work we aim to explain some unusual fragmentation steps using high-resolution MS n . For example, in the case of amiloride an intense product ion in MS 3 analysis generates an apparent loss of 10 Da. Water adduct formation and successive carbon monoxide elimination can explain this uncommon behavior, which was studied using different ion traps. Bendroflumethiazide MS n spectra show instead three successive HF losses, in spite of the presence of a radical site in the parent structure. Homolytic cleavages with radical ion production occur also in the case of protonated positive ion of ethacrynic acid (loss of chlorine radical) showing that such fragmentation behavior is not so rare as generally reported. Different ionization modes were studied and a tentative correlation with acidic-base properties was done. Multiple stage high-resolution mass spectra of positive and negative ions were discussed.

Ring‐Borylated 15‐Electron and 17‐Electron ansa‐Chromocene Complexes, their Physical Properties and Molecular Structures

A detailed study of the thermal decomposition of the zwitterionic, ring-borylated ansa-chromocene hydrido carbonyl complex [Cr(CO)H{Me(4)C(2)(C(5)H(4))[C(5)H(3)B(C(6)F(5))(3)]}] (2) is described. This complex is formed in the reaction between [Cr(CO){Me(4)C(2)(C(5)H(4))(2)}] (1) and B(C(6)F(5))(3) in toluene at -78 degrees C. Above -25 degrees C, 2 decomposes to a 50:50 mixture of the low-spin, 17e Cr(III) complexes [Cr(CO){Me(4)C(2)(C(5)H(4))[C(5)H(3)B(C(6)F(5))(3)]}] (3b) and [Cr(CO){Me(4)C(2)(C(5)H(4))(2)}][HB(C(6)F(5))(3)] (4). Carbon monoxide elimination from 3 b generates high-spin, 15 e [Cr{Me(4)C(2)(C(5)H(4))[C(5)H(3)B(C(6)F(5))(3)]}] (3a), which coordinates two other electron-donating ligands, such as xylyl isocyanide, PMe3, and PPh(2)Me to form the low-spin, 17 e electron complexes 3c, 3d, and 3e, respectively. High-spin, 15 e [Cr{Me(4)C(2)(C(5)H(4))(2)}][HB(C(6)F(5))(3)] (5) is generated by heating 3 b in toluene at 100 degrees C and periodically removing the evolved CO. Efforts to isolate more than a few X-ray quality crystals of 5 were thwarted by its tendency to form an insoluble precipitate (6) with the same molecular formula. Heating the solution of 5 at 120 degrees C results in its partial conversion (ca. 28 %) to 3a, thereby allowing the formation of 3a in yields as high as 74 % from the reaction between 1 and B(C(6)F(5))(3). The X-ray crystal structures of 3 b-e and 5 are described. Cyclic voltammetry measurements on 3 a-e reveal a dramatic reduction in the redox potentials of the complexes relative to their non-borylated analogues. DFT calculations show that this is due primarily to electrostatic stabilization of the oxidized species by the negatively charged borylate group. EPR and 19F NMR spectroscopy allow 3a to be distinguished from its Lewis base adducts 3 b-e and reveal the relative affinities of different Lewis bases for the chromium.

Cardiac output increases the rate of carbon monoxide elimination in hyperpneic but not normally ventilated dogs

The very high solubility of carbon monoxide (CO) in blood suggests that its elimination depends predominantly on ventilation and not perfusion. Nevertheless, hyperventilation is not used for CO elimination because of the adverse effects of hypocapnia. With isocapnic hyperpnea (IH), ventilation can be increased considerably without hypocapnia. This raises the issue of whether CO elimination is limited by perfusion during IH. We studied the effect of increasing cardiac output on t1/2, the half-time of decline of blood carboxyhemoglobin concentration ([COHb]), during normal ventilation (NV) and during IH. After ethics approval was received, 13 pentobarbital-anesthetized ventilated dogs were exposed to CO to increase their [COHb]. They were then ventilated with NV or IH. At each level of ventilation, dogs were randomly assigned to treatment with dobutamine (to increase cardiac output) or to no dobutamine treatment. After the return of [COHb] to control levels, each dog was re-exposed to CO and treated with the same ventilatory mode, but the alternative inotropic treatment. Gas exchange, [COHb], and hemodynamic measures were recorded during the study. Cardiac index values in the IH group were 4.1 +/- 0.5 and 8.2 +/- 1.2 l.min(-1).m(-2) without and with dobutamine infusion, respectively. Dobutamine infusion was associated with a reduction in t1/2 from 20.3 +/- 3.6 to 16.9 +/- 2.4 min (P = 0.005) in the IH group, but no change in the NV group. These findings suggest that CO elimination during IH treatment is limited at least partly by pulmonary blood flow and may therefore be further augmented by increasing cardiac output.

Hyperoxia-induced Tissue Hypoxia

Hyperoxia-induced Tissue Hypoxia

Catalytic elimination of carbon monoxide in gas streams by thermal and ozone oxidations

The catalytic activities of Pt-Pd, 0.25 wt.% Mn and 0.56 wt.% Mn coated on Al2O3 pellets during catalytic thermal oxidation and catalytic ozone oxidation were investigated. The results reveal that the activity of catalysts in catalytic ozone oxidation differed substantially from that in catalytic thermal oxidation.

Elimination of Carbon Monoxide in the Gas Streams by Dielectric Barrier Discharge Systems with Mn Catalyst

Elimination of CO in air stream using the plasma catalytic reactors was investigated. Two plasma catalytic systems were evaluated in this study, one consisting of a catalyst-bed packed in plasma zone of a dielectric barrier discharge (DBD) reactor directly (CID reactor), and the other (CAD reactor) consisting of a catalyst-bed after a DBD reactor. The examined operating parameters in this study included applied voltage, discharge power, the lengths of plasma zone and catalyst-bed, and inlet CO concentration. It was found that the glass packed DBD reactor without catalyst cannot eliminate CO in air stream effectively. When MnO x catalyst applied to DBD reactors, the removal of 1000 ppm CO can achieve to 97% by both type reactors. Under constant energy input condition, the CO removal of a CID reactor increased with the decrease of the initial CO concentration and the increase of the length of catalyst beds. In addition, the operating energy consumption of CID system was lower than that of CAD system.