Preparation of Some Homologous TEMPO Nitroxides and Oxoammonium Salts; Notes on the NMR Spectroscopy of Nitroxide Free Radicals; Observed Radical Nature of Oxoammonium Salt Solutions Containing Trace Amounts of Corresponding Nitroxides in an Equilibrium Relationship

2017 ◽  
Vol 82 (18) ◽  
pp. 9279-9290 ◽  
Author(s):  
James M. Bobbitt ◽  
Nicholas A. Eddy ◽  
Clyde X. Cady ◽  
Jing Jin ◽  
Jose A. Gascon ◽  
...  
Keyword(s):  
Free Radicals ◽  
Nmr Spectroscopy ◽  
Salt Solutions ◽  
Oxoammonium Salts ◽  
Radical Nature ◽  
Equilibrium Relationship ◽  
Oxoammonium Salt

scholarly journals RADICAL INITIATED COPOLYMERIZATION OF METHYL METHACRYLATE AND ACRYLONITRILE IN PRESENCE OF IRON COMPLEXES

2021 ◽  
Vol 64 (4) ◽  
pp. 34-41
Author(s):  
Ruslan R. Galimullin ◽  
Natalya N. Sigaeva ◽  
Sergey V. Kolesov
Keyword(s):  
Free Radicals ◽  
Nmr Spectroscopy ◽  
Methyl Methacrylate ◽  
Metal Complexes ◽  
1H Nmr Spectroscopy ◽  
Initial Rate ◽  
Iron Complexes ◽  
Active Centers ◽  
Iron Metal ◽  
Effective Constants

This article represents data on the effect of organometallic iron complexes: ferrocene, dicarbonyl dimer of cyclopentadienyl iron and tricarbonyl cyclooctatetraene iron on the copolymerization of methyl methacrylate (MMA) and acrylonitrile (AN) initiated by benzoyl peroxide. It is shown that the introduction of metal complexes and their structure affect the initial rate of copolymerization, the form of the diagrams of the composition of the obtained copolymers, and the values of the effective constants of the relative activities of the comonomers in the copolymerization of methyl methacrylate and acrylonitrile (system metallocomplex of iron – peroxide benzoyl: ferrocene – peroxide benzoyl: rММА = 1.58; rАН= 0.08 in 60 °С; rММА = 1.30; rАН = 0.05 in 50 °С; dicarbonyl dimer cyclopentadienyl iron–peroxide benzoyl: rММА = 1.36; rАН = 0.06 in 60 °С; rММА = 1.09; rАН = 0.14 in 50 °С; tricarbonyl cyclooctatetraene iron -peroxide benzoyl: rММА = 1.08; rАН = 0.15 in 60 °С; rММА = 1.14; rАН = 0.05 in 50 °С; peroxide benzoyl: rММА = 1.11; rАН = 0.07 in 60 °С; rММА = 1.11; rАН = 0.07 in 50 °С). The proportions of triadic sequences of units in copolymers, experimentally determined from 1H NMR spectroscopy, are given, as well as the calculated proportions of dyads. The presence of iron metal complexes affects the distribution of the proportions of the triad and dyad sequences of units, as well as their microstructure in copolymers. These changes are explained by the formation of macromolecules, both with the participation of free radicals and the stereospecific coordination active centers of polymerization that are formed in the presence of iron complexes.

Tandem Elimination-Oxidation of Tertiary Benzylic Alcohols with an Oxoammonium Salt

2021 ◽  
Author(s):  
Rowan Isabella Larkin Meador ◽  
Robert E Anderson ◽  
John D Chisholm
Keyword(s):  
Single Step ◽  
Allylic Oxidation ◽  
Benzylic Alcohols ◽  
Oxoammonium Salts ◽  
Oxoammonium Salt

Tertiary benzylic alcohols react with oxoammonium salts, undergoing a tandem elimination / allylic oxidation to provide an allylic ether product in a single step. This mode of reactivity provides a...

Metal-Free Synthesis of Pyrrolo[1,2-a]quinoxalines Mediated by TEMPO Oxoammonium Salts

Synthesis ◽  
2018 ◽  
Vol 50 (14) ◽  
pp. 2727-2740 ◽  
Author(s):  
Xiang-Ying Tang ◽  
Yue-fa Gong ◽  
Heng-rui Huo
Keyword(s):  
Carbonyl Compounds ◽  
One Pot ◽  
Metal Free ◽  
Oxoammonium Salts ◽  
One Pot Synthesis ◽  
Oxoammonium Salt

We herein describe a novel TEMPO oxoammonium salt initiated Pictet–Spengler reaction of imines, generated in situ from carbonyl compounds and pyrrole- or indole-containing substrates, to afford 4,5-dihydropyrrolo[1,2-a]quinoxalines or 5,6-dihydroindolo[1,2-a]quin­oxalines in good to excellent yields. Moreover, a one-pot synthesis of a biologically important quinoxaline is achieved via a cyclization–dehydrogenation process using one equivalent of the oxoammonium salt.

scholarly journals Unexpected Metal-Free Dehydrogenation of a β-Ketoester to a Phenol Using a Recyclable Oxoammonium Salt

Molbank ◽  
10.3390/m1180 ◽  
2021 ◽  
Vol 2021 (1) ◽  
pp. M1180
Author(s):  
Fabrizio Politano ◽  
William P. Brydon ◽  
Jyoti Nandi ◽  
Nicholas E. Leadbeater
Keyword(s):  
Previous Literature ◽  
Oxidative Functionalization ◽  
Dehydrogenation Reaction ◽  
Metal Free ◽  
Oxoammonium Salts ◽  
Oxoammonium Salt

The conversion of ethyl 2-oxocyclohexanecarboxylate to ethyl salicylate using an oxoammonium salt is reported. The dehydrogenation reaction is operationally simple and compares favorably with previous literature examples for the same transformation and expands the scope of oxoammonium salts as reagents for oxidative functionalization processes.

Isomorphous replacement in electron diffraction of wet crystals of rat hemoglobin

1983 ◽  
Vol 41 ◽  
pp. 446-447
Author(s):  
William F. Tivol ◽  
Murray Vernon King ◽  
D. F. Parsons
Keyword(s):  
Electron Diffraction ◽  
Heavy Atom ◽  
Isomorphous Substitution ◽  
X Ray Diffraction ◽  
Salt Solutions ◽  
X Ray ◽  
Isomorphous Replacement ◽  
Structure Factors ◽  
Diffraction Structure ◽  
The Mean

Feasibility of isomorphous substitution in electron diffraction is supported by a calculation of the mean alteration of the electron-diffraction structure factors for hemoglobin crystals caused by substituting two mercury atoms per molecule, following Green, Ingram & Perutz, but with allowance for the proportionality of f to Z3/4 for electron diffraction. This yields a mean net change in F of 12.5%, as contrasted with 22.8% for x-ray diffraction.Use of the hydration chamber in electron diffraction opens prospects for examining many proteins that yield only very thin crystals not suitable for x-ray diffraction. Examination in the wet state avoids treatments that could cause translocation of the heavy-atom labels or distortion of the crystal. Combined with low-fluence techniques, it enables study of the protein in a state as close to native as possible.We have undertaken a study of crystals of rat hemoglobin by electron diffraction in the wet state. Rat hemoglobin offers a certain advantage for hydration-chamber work over other hemoglobins in that it can be crystallized from distilled water instead of salt solutions.

Bulk standards for low-temperature biological x-ray microanalysis

1984 ◽  
Vol 42 ◽  
pp. 282-283
Author(s):  
P. Echlin ◽  
M. McKoon ◽  
E.S. Taylor ◽  
C.E. Thomas ◽  
K.L. Maloney ◽  
...  
Keyword(s):  
Phase Separation ◽  
Low Temperature ◽  
Analytical Method ◽  
Salt Solutions ◽  
Absolute Concentration ◽  
Cooling Process ◽  
X Ray ◽  
The Absolute ◽  
Analytical Procedures ◽  
Electrical Conductors

Although sections of frozen salt solutions have been used as standards for x-ray microanalysis, such solutions are less useful when analysed in the bulk form. They are poor thermal and electrical conductors and severe phase separation occurs during the cooling process. Following a suggestion by Whitecross et al we have made up a series of salt solutions containing a small amount of graphite to improve the sample conductivity. In addition, we have incorporated a polymer to ensure the formation of microcrystalline ice and a consequent homogenity of salt dispersion within the frozen matrix. The mixtures have been used to standardize the analytical procedures applied to frozen hydrated bulk specimens based on the peak/background analytical method and to measure the absolute concentration of elements in developing roots.

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