Spontaneous Deoxygenation Research Articles

Atomistic Details of Methyl Linoleate Pyrolysis: Direct Molecular Dynamics Simulation of Converting Biodiesel to Petroleum Products

Dependence on petroleum and petrochemical products is unsustainable; it is both a finite resource and an environmental hazard. Biodiesel has many attractive qualities, including a sustainable feedstock; however, it has its complications. The pyrolysis (a process already in common use in the petroleum industry) of biodiesel has demonstrated the formation of smaller hydrocarbons comprising many petrochemical products but experiments suffer from difficulty quantifying the myriad reaction pathways followed and products formed. A computational simulation of pyrolysis using “ab initio molecular dynamics” offers atomic-level detail of the reaction pathways and products formed. Herein, the most prevalent fatty-acid ester (methyl linoleate) from the most prevalent feedstock for biodiesel in the United States (soybean oil) is studied. Temperature acceleration within the atom-centered density matrix propagation formalism (Car–Parrinello) utilizing the D3-M06-2X/6-31+G(d,p) model chemistry is used to compose an ensemble of trajectories. The results are grounded in comparison to experimental studies through agreement in the following: (1) the extent of reactivity (40% in the experimental and 36.1% in this work), (2) the homology of hydrocarbon products formed (wt % of C6–C10 products), and (3) the CO/CO2 product ratio. Deoxygenation pathways are critically analyzed (as the presence of oxygen in biodiesel represents a disadvantage in its current use). Within this ensemble, deoxygenation was found to proceed through two subclasses: (1) spontaneous deoxygenation, following one of four possible pathways; or (2) induced deoxygenation, following one of three possible pathways.

CO2 Photoreduction Activity Enhancement and Unexpected Observation of Carbon Monoxide Adsorbates on the Surface of TiO2 Nanotube Arrays Synthesized in Formamide Electrolytes.

TiO2 nanotube arrays grown through electrochemical anodization in a formamide-based electrolyte (TNTA-FA) exhibited a whole host of unusual properties compared to nanotubes grown in the conventional ethylene glycol-based electrolyte (TNTA-EG). TNTA-FA exhibited shorter phonon lifetimes, lower lattice strain, more visible light absorption, lower work function, and a highly unusual adsorbate structure consisting of physisorbed and chemisorbed CO along with linearly adsorbed CO2 and various monodentate and bidentate carbonate species. The observation of adsorbed CO in the dark is highly unusual and indicates spontaneous deoxygenation of CO2 on the surface of TNTA-FA. The significance of this finding is that the formation of CO2•- is no longer the rate-limiting bottleneck for the reduction of CO2 on TNTA-FA surfaces as it is for all TiO2 surfaces. TNTA-FA samples are strongly colored (inclusive of a fluorescent green color) and consist of rounded, vertically oriented hollow cylinders as opposed to the honeycomb-like morphology of TNTA-EG arranged in an approximate triangular lattice. The photocatalytic activity was tested through the CO2 photoreduction and dye degradation tests. Formamide-based nanotubes outperformed the EG-based nanotubes by almost 1.7 and 2 times, respectively, in CO2 reduction and dye degradation tests done on methylene blue, brilliant green, and rhodamine B dyes. These results are attributed to stronger surface band bending in TNTA-FA which facilitates more efficient separation of photogenerated electron-hole pairs.

MR Relaxation Studies of Hemoglobin Aggregation Process in Sickle Cell Disease: Application for Diagnostics and Therapeutics

Sickle cell disease (SCD) is a blood disorder, which has been studied using different research methods including linear birefringence, electronic microscopy, viscosity determination, Electron Paramagnetic Resonance and Nuclear Magnetic Resonance. We summarized in this paper the contribution of proton magnetic relaxation, to the study of the behavior of the protons from protein and water as a consequence of hemoglobin S (HbS) polymerization. Spin–Lattice (T1) and Spin–Spin (T2) relaxation times have been sensitive to the agglutination of the HbS, having a decreasing behavior because of this process. T2 has shown a stronger sensitivity, decreasing immediately during deoxygenation in red blood cells (RBC) of patients homozygous for HbS and in pure HbS solution with intracellular concentration. In the HbS solutions with hemoglobin concentration below 208 mg/mL and heterozygous RBC, during induced deoxygenation, the Spin–Spin relaxation time was characterized by a delay time before polymerization, a decrease during aggregation and a further stabilization; the same occurs in the HbS solutions under spontaneous deoxygenation. The fast exchange of water molecules between the bound and free state, as well as the dipolar interaction between the protons inside the water molecules, were utilized to explain the relaxation times behavior; an increase in the correlation time of the strongly bound water was found. Contradictory results were observed between the experimental behavior obtained for T1 and those results predicted theoretically. T2 behavior showed utility to evaluate the clinical state of the SCD patients and the effect of vanillin and Hydroxyurea on the HbS polymerization.

Interaction of a lithiated nitronyl nitroxide with polyfluorinated 1,4-naphthoquinones

A 4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl lithium derivative was found to react with 2-methoxypentafluoro-1,4-naphthoquinone to form a product of addition at the carbonyl function: radical 2-(3,5,6,7,8-pentafluoro-1-hydroxy-2-methoxy-4-oxo-1,4-dihydronaphthalen-1-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl. The yield of the addition product increased with temperature and reached 84% at 0 °C. The reaction of the lithium derivative with hexafluoro-1,4-naphthoquinone gave rise to a product of addition at both carbonyl groups, namely, nitronyl nitroxide diradical 2,3,5,6,7,8-hexafluoro-1,4-bis(4,4,5,5-tetramethyl-3-oxide-1-oxyl-4,5-dihydro-1H-imidazole-2-yl)-1,4-dihydronaphthalene-1,4-diol in a 16% yield. The structures of both mono- and diradical were solved by X-ray diffraction analysis, which revealed formation of an intramolecular H-bond between the OH group and nitroxide oxygen. According to electron paramagnetic resonance (EPR) spectroscopy, the obtained mono- and dinitroxide are prone to spontaneous deoxygenation in a toluene solution to give corresponding iminonitroxides. In water, they are much more stable.

H2 Production Mediated by CO2 via Initial Reduction to Formate

A Ru(NH-NHC) complex with an open coordination site on the metal center adjacent to ligand N–H moieties has been synthesized and characterized. This complex exhibits unique reactivity upon reaction with either CO2 or NaHCO3, yielding a formate-bridged bimetallic complex via a spontaneous deoxygenation reaction and formal reduction at carbon. Dehydrogenation of the formate complex leads to a Ru–carbamate species following carbon–nitrogen bond formation between the CO2 moiety and the NHC ligand. This reactivity opens up new pathways for CO2 reduction and is relevant to H2 storage.

Water Efflux in Red Blood Cells of Sickle Cell Patients under Spontaneous Deoxygenation

The water transport through Red Blood Cells (RBC) membrane has been previously studied in Sickle Cell Disease (SCD) using oxygenated RBC or under complete deoxygenation. In this work, the water efflux in RBC of sickle cell patients was studied under spontaneous deoxygenation conditions. With that purpose, a magnetic resonance method was used to evaluate the water exchange time (τe) and the permeability through the erythrocyte membrane (P) measuring the spin-spin relaxation time (T2) in doped and non-doped RBC. Carr-Purcell-Meiboon-Gill (CPMG) pulse sequence was used to measure T2 in a magnetic resonance console coupled to one homogeneous magnet system (0.095 T). An increase of the water transport in RBC from sickle cell patients was observed and characterized with a τe value of 15.2 ± 0.8 ms. The abnormal activation of the Psickle, Gardos, and potassium chloride cotransporter channels starting from deoxygenation, as well as, the possible appearance of new pores due to the increase of the hemoglobin-membrane interaction, are suggested to explain this abnormal transport phenotype. The change of the water volume to surface ratio (V/S) in the sickle cells is also suggested to be considered in P calculation under deoxygenation. The results obtained in this work increase the fundamental knowledge about molecular mechanism involved in SCD and could be useful in the development of new methods for diagnostic and treatment evaluation.

Spin Label Studies of the Hemoglobin–Membrane Interaction During Sickle Hemoglobin Polymerization

An enhanced hemoglobin–membrane association has been previously documented in sickle cell anemia. However, it is not known how this interaction is modified during the hemoglobin S polymerization process. In this work, we use a model of reconstituted erythrocytes from ghost membranes whose cytoskeleton proteins had been previously labeled with the 4-maleimido Tempo spin label, and that were subsequently resealed with hemoglobin S or A solutions. Using electron paramagnetic resonance spectroscopy, we studied the time dependence of the spectral W/S parameter, indicative of the conformational state of cytoskeleton proteins (mainly spectrin) under spontaneous deoxygenation, with the aim of detecting the eventual effects due to hemoglobin S polymerization. The differences observed in the temporal behavior of W/S in erythrocytes reconstituted with both hemoglobins were considered as experimental evidence of an increment in hemoglobin S–membrane interaction as a result of the polymerization process of hemoglobin S under spontaneous deoxygenation.

Sickle Cell Disease Painful Crisis and Steady State Differentiation by Proton Magnetic Resonance

The delay time of the Hb S polymerization process was investigated in 63 patients with sickle cell disease during steady state and 10 during painful crisis starting from spin–spin proton magnetic resonance (PMR) time behavior measured at 36°C and during spontaneous deoxygenation. We found a significant decrease of delay time as a result of the crisis (36 ± 10%) and two well-differentiated ranges of values for each state: 273–354 min for steady state and 166–229 min for crisis with an uncertainty region of 15%. It is possible to use PMR as an objective and quantitative method in order to differentiate both clinical conditions of the sickle cell patient, but a more clear differentiation can be established comparing the delay time (td) value of one patient during crisis with his own td value during steady state.

Deuterium Magnetic Relaxation Process during the Polymerization of Hemoglobin S

The deuterium and the proton spin–spin relaxation times are investigated at 4 MHz in partially deuterated samples of hemoglobin A and S at 36 °C during spontaneous deoxygenation. Deuterium relaxation shows a sigmoidal behavior describing the three characteristic phases of hemoglobin S (HbS) polymerization. The coincidence between the behaviors of deuterium and proton relaxation supports the dominant effect of agglutination on macromolecular mobility. Evidences of an increase of the internal electric field gradient and the appearance of a modified charge distribution inside the HbS solution, as a result of the polymerization process under spontaneous deoxygenation, were not found.

EPR study of the hemoglobin rotational correlation time and microviscosity during the polymerization of hemoglobin S

The microviscosity and the protein rotational correlation time are analyzed in samples of hemoglobin A and hemoglobin S with the intracellular concentration at 36°C and during spontaneous deoxygenation. With this purpose, we use glutathione and carbonmonoxy hemoglobin labeled with 4-maleimido-2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO) as probes and 4-maleimido TEMPO bound to the hemoglobin (A and S) as a spin label. The saturation transfer electron paramagnetic resonance experiment showed a sigmoidal behavior, and an increase (about twice) of the hemoglobin rotational correlation time and microviscosity during the polymerization process of hemoglobin S. The delay time determined by this method coincides with that obtained in proton magnetic resonance experiments. These results help to explain the temporal behavior of the proton relaxation times obtained in samples of hemoglobin A and S under the same experimental conditions.

Proton magnetic relaxation process during the polymerization of hemoglobin S

The proton spin-lattice and spin-spin magnetic relaxation times are investigated at 4 MHz in samples of hemoglobin A and S with intracellular concentrations, at 36 °C, and during spontaneous deoxygenation. Magnetic relaxation behaves differently in the solutions of hemoglobin A and S. The possible causes of this behavior are discussed: changes in molecular mobility, the variations of hemoglobin magnetism, and the appearance of microinhomogeneities in the solutions of hemoglobin S at the end of the polymerization process.

ChemInform Abstract: Spontaneous Deoxygenation of the Addition Compounds of RYbI (R: Me, Ph) to p‐Benzoquinone.

ChemInformVolume 18, Issue 24 Preparative Organic Chemistry ChemInform Abstract: Spontaneous Deoxygenation of the Addition Compounds of RYbI (R: Me, Ph) to p-Benzoquinone. O. P. SYUTKINA, O. P. SYUTKINA Fiz.-khim. inst. im. Karpova, MoskvaSearch for more papers by this authorL. F. RYBAKOVA, L. F. RYBAKOVA Fiz.-khim. inst. im. Karpova, MoskvaSearch for more papers by this authorE. S. PETROV, E. S. PETROV Fiz.-khim. inst. im. Karpova, MoskvaSearch for more papers by this authorI. P. BELETSKAYA, I. P. BELETSKAYA Fiz.-khim. inst. im. Karpova, MoskvaSearch for more papers by this author O. P. SYUTKINA, O. P. SYUTKINA Fiz.-khim. inst. im. Karpova, MoskvaSearch for more papers by this authorL. F. RYBAKOVA, L. F. RYBAKOVA Fiz.-khim. inst. im. Karpova, MoskvaSearch for more papers by this authorE. S. PETROV, E. S. PETROV Fiz.-khim. inst. im. Karpova, MoskvaSearch for more papers by this authorI. P. BELETSKAYA, I. P. BELETSKAYA Fiz.-khim. inst. im. Karpova, MoskvaSearch for more papers by this author First published: June 16, 1987 https://doi.org/10.1002/chin.198724136Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume18, Issue24June 16, 1987 RelatedInformation

Spontaneous deoxygenation of the products of the addition of MeYbI and PhYbI to para-benzoquinone

1. The addition of MeYbl at both CO groups of p-benzoquinone is accompanied by the spontaneous deoxygenation of the dicarbinolate to p-xylene. The deoxygenation of the initially formed monocarbinolate leads to toluene and its derivatives. 2. In the case of PhYbl, the deoxygenation of the monocarbinolate proceeds so much more rapidly than the addition of the organolanthanide at the second CO group of p-benzoquinone that the major reaction product is biphenyl.

ChemInform Abstract: SPONTANEOUS DEOXYGENATION OF N‐(3,4‐METHYLENEDIOXYBENZYL)‐ACETOHYDROXAMIC ACID‐ AN EXCEPTIONALLY FACILE PROCESS

An exceptionally facile spontaneous deoxygenation of N-(3,4-methylenedioxybenzyl)-acetohydroxamic acid to its corresponding amide, without apparent literature precedent, is reported.

Spontaneous deoxygenation of N-(3,4-methylenedioxybenzyl)-acetohydroxamic Acid: An exceptionally facile process

An exceptionally facile spontaneous deoxygenation of N-(3,4-methylenedioxybenzyl)-acetohydroxamic acid to its corresponding amide, without apparent literature precedent, is reported.