Kinetics of the detritiation of [10,10-3H] mianserin and related compounds in highly basic media

1990 ◽  
Vol 68 (10) ◽  
pp. 1818-1820
Author(s):  
John R. Jones ◽  
David A. Wickenden ◽  
Carel W. Funke ◽  
Frans M. Kaspersen
Keyword(s):  
Spectroscopic Analysis ◽  
Exchange Process ◽  
Apparent Increase ◽  
H Nmr ◽  
Kinetics Of ◽  
Related Compounds

A recently developed procedure (Buist etal., J. Chem. Soc. Perkins II, 169 (1990)) has been used to study the kinetics of detritiation of [10,10-3H] mianserin and two other structurally related compounds in highly basic media. Over the H− range 16–20 the stereoselectivity of the exchange process keq/kax for all three compounds is virtually constant (5 ± 1). The apparent increase at still higher basicities is associated with distinct curvature in the log k vs. H− plots, indicating the onset of another mechanism. Partial detritiation studies at higher levels of radioactivity, when combined with 3H nmr spectroscopic analysis, confirms the greater lability of the C-10 (or C-9) equatorial hydrogen. Keywords: detritiation, high basic media, mianserin.

Synthesis and Structure Assignment of 2-(4-Methoxybenzyl)cyclohexyl β-D-Glucopyranoside Enantiomers

2006 ◽  
Vol 71 (10) ◽  
pp. 1470-1483 ◽  
Author(s):  
David Šaman ◽  
Pavel Kratina ◽  
Jitka Moravcová ◽  
Martina Wimmerová ◽  
Zdeněk Wimmer
Keyword(s):  
Analytical Data ◽  
Chiral Hplc ◽  
Nmr Analysis ◽  
Target Structure ◽  
Enantiomerically Pure ◽  
Whole Cells ◽  
H Nmr ◽  
Structure Assignment ◽  
Related Compounds ◽  
C Nmr

Glucosylation of the cis- and trans-isomers of 2-(4-methoxybenzyl)cyclohexan-1-ol (1a/1b, 2a/2b, 1a or 2a) was performed to prepare the corresponding alkyl β-D-glucopyranosides, mainly to get analytical data of pure enantiomers of the glucosides (3a-6b), required for subsequent investigations of related compounds with biological activity. One of the employed modifications of the Koenigs-Knorr synthesis resulted in achieving 85-95% yields of pure β-anomers 3a/3b, 4a/4b, 3a or 4a of protected intermediates, with several promoters and toluene as solvent, yielding finally the deprotected products 5a/5b, 6a/6b, 5a or 6a as pure β-anomers. To obtain enantiomerically pure β-anomers of the target structure (3a, 4a, 5a and 6a) for unambiguous structure assignment, an enzymic reduction of 2-(4-methoxybenzyl)cyclohexan-1-one by Saccharomyces cerevisiae whole cells was performed to get (1S,2S)- and (1S,2R)-enantiomers (1a and 2a) of 2-(4-methoxybenzyl)cyclohexan-1-ol. The opposite enantiomers of alkyl β-D-glucopyranosides (5b and 6b) were obtained by separation of the diastereoisomeric mixtures 5a/5b and 6a/6b by chiral HPLC. All stereoisomers of the products (3a-6b) were subjected to a detailed 1H NMR and 13C NMR analysis.

scholarly journals Polyelectrolyte Gels: A Unique Class of Soft Materials

Gels ◽  
2021 ◽  
Vol 7 (3) ◽  
pp. 102
Author(s):  
Ferenc Horkay
Keyword(s):  
Exchange Process ◽  
Interaction Strength ◽  
Soft Materials ◽  
Industrial Applications ◽  
Future Research ◽  
Swelling Kinetics ◽  
Polyelectrolyte Gels ◽  
Ion Exchange Process ◽  
Counter Ions ◽  
Kinetics Of

The objective of this article is to introduce the readers to the field of polyelectrolyte gels. These materials are common in living systems and have great importance in many biomedical and industrial applications. In the first part of this paper, we briefly review some characteristic properties of polymer gels with an emphasis on the unique features of this type of soft material. Unsolved problems and possible future research directions are highlighted. In the second part, we focus on the typical behavior of polyelectrolyte gels. Many biological materials (e.g., tissues) are charged (mainly anionic) polyelectrolyte gels. Examples are shown to illustrate the effect of counter-ions on the osmotic swelling behavior and the kinetics of the swelling of model polyelectrolyte gels. These systems exhibit a volume transition as the concentration of higher valence counter-ions is gradually increased in the equilibrium bath. A hierarchy is established in the interaction strength between the cations and charged polymer molecules according to the chemical group to which the ions belong. The swelling kinetics of sodium polyacrylate hydrogels is investigated in NaCl solutions and in solutions containing both NaCl and CaCl2. In the presence of higher valence counter-ions, the swelling/shrinking behavior of these gels is governed by the diffusion of free ions in the swollen network, the ion exchange process and the coexistence of swollen and collapsed states.

scholarly journals Isocyanate und verwandte Verbindungen des trimeren Phosphornitriddifluorids / Isocyanates and Related Compounds of Trimeric Phosphor-difluoronitride

1971 ◽  
Vol 26 (7) ◽  
pp. 679-683 ◽  
Author(s):  
Herbert W. Roesky ◽  
Enno Janssen
Keyword(s):  
Ir Spectra ◽  
Elemental Analysis ◽  
Mass Spectra ◽  
H Nmr ◽  
Carbonic Acids ◽  
Related Compounds

P3N3F5NCO was prepared by reaction of P3N3F5NSO with (COCl) 2. Substituted amides were obtained from the reaction of P3N3F5NSO with carbonic acids e. g. P3N3F5NHCOCH3, P3N3F5NHCOC2H5, and P3N3F5NHCOC3H7. If these substances were treated with PCl5 the following compounds P3N3F5N = CClCH3, P3N3F5N = CClCH5, and P3N3F5TN = CClC3H7 were formed. They reacted with nucleophiles to give P3N3F5N = CNH2CH3, P3N3F5N = TN (CH3) 2C2H5, and P3N3F5N = CN (CH3) 2CH7. The properties of these compounds are described. They were characterized by elemental analysis and IR-spectra. 19F-, 1H-NMR, and mass spectra are reported.

The kinetics of the penetration of some representative anthelmintics and related compounds into Ascaris lumbricoides var. suis

Parasitology ◽  
1949 ◽  
Vol 39 (3-4) ◽  
pp. 281-290 ◽  
Author(s):  
A. R. Trim
Keyword(s):  
Ascaris Lumbricoides ◽  
Homogeneous Layer ◽  
Outermost Layer ◽  
Basic Group ◽  
Rate Of Penetration ◽  
Surface Active ◽  
Main Barrier ◽  
Kinetics Of ◽  
Related Compounds ◽  
Active Substances

1. The rate of penetration of some representative drugs into Ascaris lumbricoides var. suis has been measured.2. The series of 4-n-alkyl resorcinols shows a typical homologous series effect.3. l-Nicotine penetrates relatively slowly.4. Its rate of penetration is greatly influenced by the extent of dissociation of its methyl pyrrolidine basic group.5. The rate of penetration of nicotine is greatly accelerated in the presence of some surface active substances.6. Chloroform is the most rapidly penetrating substance studied, and its penetration is not significantly influenced by the presence of proteins, carbohydrates and fats and their products of digestion.7. An analysis of the experimental results shows that the outermost layer of the cuticle of Ascaris is probably the main barrier to penetration. It behaves as if it were a thin; homogeneous layer of lipoid.8. The significance of these results in the study of anthelmintics is assessed.

High field 1H NMR Studies of Sol-Gel Kinetics

1986 ◽  
Vol 73 ◽  
Author(s):  
Bruce D. Kay ◽  
Roger A. Assink
Keyword(s):  
Equilibrium Distribution ◽  
Sol Gel ◽  
Nmr Studies ◽  
H Nmr ◽  
Rate Limiting Step ◽  
Rate Of Hydrolysis ◽  
Acid Catalyzed ◽  
Product Species ◽  
Rate Limiting ◽  
Kinetics Of

ABSTRACTHigh resolution 1H NMR spectroscopy at high magnetic fields is employed to study the reaction kinetics of the Si(OCH3)4:CH3OH:H2O sol-gel system. Both the overall extent of reaction as a function of time and the equilibrium distribution of species are measured. In acid catalyzed solution, condensation is the rate limiting step while in base catalyzed solution, hydrolysis becomes rate limiting. A kinetic model in which the rate of hydrolysis is assumed to be independent of the adjacent functional groups is presented. This model correctly predicts the distribution of product species during the initial stages of the sol-gel reaction.

scholarly journals Kinetics of radical telomerization of acrylic acid in the presence of 1-octadecanethiol

2018 ◽  
Vol 90 (11) ◽  
pp. 1743-1754 ◽  
Author(s):  
Yaroslav O. Mezhuev ◽  
Oksana Y. Sizova ◽  
Yuri V. Korshak ◽  
Anna L. Luss ◽  
Ivan V. Plyushchii ◽  
...  
Keyword(s):  
Critical Micelle Concentration ◽  
Acrylic Acid ◽  
Monomer Concentration ◽  
Atom Economy ◽  
Exponential Factor ◽  
H Nmr ◽  
Radical Telomerization ◽  
Kinetics Of ◽  
End Group ◽  
C Nmr

AbstractThe oligomer of acrylic acid with a thiooctadecyl end-group was obtained by using octadecyl mercaptan as the chain-transfer agent. The resulting oligomer was characterized by 1H NMR and 13C NMR spectroscopy and critical micelle concentration was determined in aqueous solution. The order with respect to the initiator concentration was 0.5 and 1.6 with respect to the monomer concentration. The abnormal reaction order with respect to the monomer concentration was explained by participation in the chain propagation of unassociated and associated forms of acrylic acid, which were stabilized by formation of hydrogen bonds. The kinetic parameters of telomerization were determined. Telomerization with acrylic acid in the non-associated form had lower activation energy and lower pre-exponential factor than in the case of associated forms. The synthesis of the acrylic acid oligomer with a thiooctadecyl end-group having a low critical micelle concentration in water was carried out in one stage and corresponds to the concept of atom economy.

scholarly journals Study of the coordination of quinuclidine to a chiral zinc phthalocyanine dimer

2016 ◽  
Vol 20 (08n11) ◽  
pp. 1224-1232 ◽  
Author(s):  
Nelson Giménez-Agulló ◽  
Gemma Aragay ◽  
José Ramón Galán-Mascarós ◽  
Pablo Ballester
Keyword(s):  
Chemical Exchange ◽  
Variable Temperature ◽  
Exchange Process ◽  
Zinc Phthalocyanine ◽  
Hydrogen Atoms ◽  
Dimerization Constant ◽  
H Nmr ◽  
Dimerization Process ◽  
Nmr Titrations ◽  
Millimolar Concentration

We attempted the calculation of an accurate equilibrium constant for the dimerization process of enantiomerically pure Zn-1 using UV-vis dilution experiments. At millimolar concentration Zn-1 is involved in a chemical exchange process between its monomeric and dimeric state that is slow on the 1H NMR timescale. We performed variable-temperature 1H NMR experiments in CDCl3 solution to determine the dimerization constant value at different temperatures and performed a van’t Hoff plot to derive the thermodynamic parameters of the process. The calculated thermodynamic data revealed that the dimerization process is entropy-driven and enthalpically opposed. We also probed the coordination of quinuclidine, 1-azabicyclo[2.2.2]octane, 2, to the Zn-1 using UV-vis and 1H NMR titrations in CDCl3 solution. At micromolar concentration the Zn-1 exclusively exists in solution as a monomer and forms a simple 1:1, [Formula: see text], complex with quinuclidine having a stability constant of [Formula: see text]([Formula: see text]) [Formula: see text] 106 M[Formula: see text]. On the other hand, the 1H NMR titrations carried out at 298 K and at millimolar concentration showed that Zn-1 was present in solution as the dimer and formed 1:2, [Formula: see text], and 2:2, [Formula: see text] complexes by coordination to 2. In addition, the 1:1 complex, [Formula: see text] showed a reduced dimerization constant compared to the uncoordinated parent monomer Zn-1. At high quinuclidine concentration, the 1:1 complex, [Formula: see text], derived from the coordinated dimer dissociation was also detected. The 1H NMR spectra of the titrations displayed separate signals for some hydrogen atoms of the Zn-phthalocyanine in each one of the four species. Remarkably, the chemical exchange processes involving free and bound quinuclidine in the monomeric and dimeric complexes showed different kinetics on the NMR timescale.

scholarly journals Kinetic Analysis of the Hydrolysis of Pentose-1-Phosphates Through Apparent Nucleoside Phosphorolysis Equilibrium Shifts

2020 ◽  
Author(s):  
Felix Kaspar ◽  
Peter Neubauer ◽  
Anke Kurreck
Keyword(s):  
Kinetic Analysis ◽  
Hydrolysis Kinetics ◽  
Equilibrium Thermodynamics ◽  
Apparent Increase ◽  
Equilibrium Conversion ◽  
Sugar Phosphates ◽  
Kinetics Of ◽  
Hydrolysis Of

<div>Ask what an equilibrium can do for you:</div><div>Hydrolysis of pentose-1-phosphates leads to an apparent increase of the equilibrium conversion in nucleoside phosphorolysis reactions. This information can be leveraged via equilibrium thermodynamics to determine the hydrolysis kinetics of in situ generated sugar phosphates, which are known to be elusive and difficult to quantify.<br></div>

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