Organocatalyzed Selective C-D/C-H Exchange Reactions in Conjugated Triene

2015 ◽  
Vol 12 (3) ◽  
pp. 181-186
Author(s):  
Isao Yamaguchi ◽  
Mikihiko Minamitani
Keyword(s):  
Exchange Reactions ◽  
Conjugated Triene

Exchange reactions and electrolytic dissociation

1948 ◽  
Vol 45 ◽  
pp. 147-149 ◽  
Author(s):  
C. C. Evans ◽  
S. Sugden
Keyword(s):  
Exchange Reactions ◽  
Electrolytic Dissociation

Modeling of photosynthesis light curves by linear splines

2019 ◽  
pp. 20-29
Author(s):  
Alexander S. Lelekov ◽  
Rudolf P. Trenkenshu
Keyword(s):  
Experimental Data ◽  
Chlorophyll A ◽  
Skeletonema Costatum ◽  
Light Flux ◽  
Photosynthesis Rate ◽  
Light Curves ◽  
External Irradiation ◽  
Exchange Reactions ◽  
Cell Adaptation ◽  
Linear Splines

The paper presents an example of the linear splines use to describe the photosynthesis light curves for microalgae culture. The main mathematical models of the relationship between photosynthesis rate and light are listed. Based on the previously formulated basic principles of modeling microalgae photobiosynthesis, a mathematical model is proposed that describes the dependence of the assimilation number of chlorophyll a on the value of the light flux by linear splines. The advantage of the proposed approach is a clear definition of the point of change of the limiting factor. It is shown that light-limited photosynthesis rate is determined not only by external irradiation, but also by the concentration of chlorophyll a. The light-saturated rate depends on the amount of a key enzyme complex, which limits the rate of energy exchange reactions in the cell. Verification of the proposed model on the example of the diatom microalgae Skeletonema costatum was carried out. It is shown that the higher the degree of cell adaptation to high irradiation, the better the photosynthesis curve is described by linear splines. If S. costatum cells are adapted to low irradiation, deviations of experimental data from the idealized broken line are observed, which are caused by changes in the pigment composition. When the experimental data are normalized, the cell adaptation factor is reduced, all points are described by a single broken line, which indicates the universality of the proposed approach.

β-Diketone chelates of bis(ethylene)rhodium and products of exchange reactions with chloro-substituted dienes

1972 ◽  
Vol 37 (9) ◽  
pp. 3081-3089 ◽  
Author(s):  
K. Bouchal ◽  
J. Škramovská ◽  
P. Schmidt ◽  
F. Hrabák
Keyword(s):  
Exchange Reactions

Voltammetric Studies of Some Novel Fe(III) Complexes with Quadridentate Ligands. The Axial Ligand-Exchange Reactions in DMF and DMSO

1995 ◽  
Vol 60 (7) ◽  
pp. 1140-1157 ◽  
Author(s):  
Ljiljana S. Jovanovic ◽  
Luka J. Bjelica
Keyword(s):  
Oxidation State ◽  
Chemical Reactions ◽  
Ligand Exchange ◽  
Kinetic Data ◽  
Central Atom ◽  
Axial Ligand ◽  
Exchange Reactions ◽  
Ligand Effect ◽  
Condensation Products ◽  
Voltammetric Studies

The electrochemistry of four novel Fe(III) complexes of the type [Fe(L)Cl], involving quadridentate ligands based on the condensation products of benzoylacetone-S-methylisothiosemicarbazone with salicylaldehyde, 5-chlorosalicylaldehyde, 3,5-dichlorosalicylaldehyde or 5-nitrosalicylaldehyde, was studied in DMF and DMSO at a GC electrode. All complexes undergo a two-step one-electron reductions, usually complicated by chemical reactions. In solutions containing Cl-, the ligand-exchange reactions Cl--DMF and Cl--DMSO take place. Stability of the chloride-containing complexes was discussed in terms of the coordinated ligand effect, oxidation state of the central atom and, in particular, of the donor effect of the solvent. Some relevant kinetic data were calculated.

Transalkylierung und protonenkatalysierte C-C-Spaltung bei n-Butyl-und n-Pentylbenzol in der Gasphase / Transalkylation and Proton Catalyzed C-C-Cleavage of Gaseous n-Butyl and w-Pentyl Benzenes

1979 ◽  
Vol 34 (3) ◽  
pp. 495-501 ◽  
Author(s):  
C. Wesdemiotis ◽  
H. Schwarz ◽  
C. C. Van de Sande ◽  
F. Van Gaever
Keyword(s):  
Hydrogen Exchange ◽  
Closed Shell ◽  
Open Shell ◽  
Molecular Ions ◽  
Exchange Reactions ◽  
Intramolecular Exchange ◽  
Carbon Carbon Bond ◽  
Exchange Processes ◽  
Reaction Channels ◽  
Alkyl Benzenes

Abstract The investigation of several 13carbon and deuterium labelled n-butyl and n-pentyl benzenes demonstrate that chemical ionization (reagent gas: methane) induces specific carbon-carbon bond cleavages of the alkyl group. The extent of competing reaction channels as for instance direct alkene elimination versus dealkylation/reprotonation is analyzed. Partial hydrogen exchange processes between reagent ions and substrate molecules are restricted to the phenyl ring. Intramolecular exchange reactions between the side chain and the aromatic ring which are typical for the open shell molecular ions of alkyl benzenes are not observed for analogous closed shell cations.

Studies on the alcohol exchange reactions of methoxide ditungsten [W(IV)] compound W2Cl4(OCH3)4 (CH3OH)2, prepared from (n-Bu4N)3W2Cl9

1990 ◽  
Vol 8 (6) ◽  
pp. 520-528
Author(s):  
Bo Hong ◽  
Song-Lin Jin ◽  
Ku Yih-Tong Gu Yi-Dong ◽  
Ming-Qin Chen
Keyword(s):  
Exchange Reactions

scholarly journals F/OH ratio in a rare fluorine-poor blue topaz from Padre Paraíso (Minas Gerais, Brazil) to unravel topaz’s ambient of formation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
N. Precisvalle ◽  
A. Martucci ◽  
L. Gigli ◽  
J. R. Plaisier ◽  
T. C. Hansen ◽  
...  
Keyword(s):  
Supercritical Fluids ◽  
Fluorine Content ◽  
Minas Gerais ◽  
Hydroxyl Groups ◽  
Exchange Reactions ◽  
Silicate System ◽  
Mullite Phase ◽  
Anomalous Water

AbstractTopaz [Al2SiO4(F,OH)2] is one of the main fluorine-bearing silicates occurring in environments where variably acidic (F)/aqueous (OH) fluids saturate the silicate system. In this work we fully characterized blue topaz from Padre Paraíso (Minas Gerais, Brazil) by means of in situ synchrotron X-Ray and neutron powder diffraction measurements (temperature range 298–1273 K) combined with EDS microanalyses. Understanding the role of OH/F substitution in topaz is important in order to determine the hydrophilicity and the exchange reactions of fluorine by hydroxyl groups, and ultimately to characterize the environmental redox conditions (H2O/F) required for mineral formation. The fluorine content estimated from neutron diffraction data is ~ 1.03 a.f.u (10.34 wt%), in agreement with the chemical data (on average 10.0 wt%). The XOH [OH/(OH + F)] (0.484) is close to the maximum XOH value (0.5), and represents the OH- richest topaz composition so far analysed in the Minas Gerais district. Topaz crystallinity and fluorine content sharply decrease at 1170 K, while mullite phase starts growing. On the basis of this behaviour, we suggest that this temperature may represent the potential initial topaz’s crystallization temperature from supercritical fluids in a pegmatite system. The log(fH2O/fHF)fluid (1.27 (0.06)) is coherent with the fluorine activity calculated for hydrothermal fluids (pegmatitic stage) in equilibrium with the forming mineral (log(fH2O/fHF)fluid = 1.2–6.5) and clearly different from pure magmatic (granitic) residual melts [log(fH2O/fHF)fluid < 1]. The modelled H2O saturated fluids with the F content not exceeding 1 wt% may represent an anomalous water-dominant / fluorine-poor pegmatite lens of the Padre Paraíso Pegmatite Field.

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