Efficient oxidations and photooxidations with molecular oxygen using metal phthalocyanines as catalysts and photocatalysts

Metal phthalocyanines can be very efficient as catalysts and photocatalysts in oxidation reactions using molecular oxygen as oxidant. Different types of soluble low molecular weight or oligomeric and insoluble heterogeneous catalysts and photocatalysts were developed. The heterogeneous metal phthalocyanines exist either impregnated on SiO 2, Al 2 O 3, charcoal and TiO 2 or covalently and coordinatively bound on SiO 2 and organic polymers or ionically bound on an organic ion exchanger. The catalytic oxidations of toxic sulfide and thiol derivative are studied. In addition, toxic phenols were employed as substrates for the photooxidation. Heterogeneous catalysts can exhibit higher activities then low molecular weight phthalocyanines. These systems exhibit a good stability for re-use. Photooxidations are more efficient than oxidations. A Si(IV) phthalocyanine derivative on a polymer ion exchanger is most active and stable. Also some examples for photooxidations in the direction of photochemical synthesis are given.

Download Full-text

Asymmetric Michael addition using sugar derived organocatalysts

Science Vision ◽

10.33493/scivis.17.04.02 ◽

2017 ◽

Vol 17 (4) ◽

pp. 182-196

Author(s):

P.B. Lalthanpuii ◽

C. Lalhriatpuia ◽

K. Vanlaldinpuia

Keyword(s):

Molecular Weight ◽

Asymmetric Synthesis ◽

Present Article ◽

Asymmetric Catalysis ◽

Michael Addition ◽

Metal Contamination ◽

Low Molecular Weight ◽

Asymmetric Transformations ◽

Asymmetric Michael Addition ◽

Different Types

Sugars are low-molecular-weight carbohydrates which consist of polyhydroxyl and carbonyl (aldehyde or ketone) functional groups. Different types of compounds derived from sugars have been used extensively as powerful and effective catalysts for asymmetric synthesis. They are readily available at a reasonable price, easily prepared, no metal contamination and are inert towards moisture and air. They are highly functionalized and have well defined stereogenic centres. Most of them are employed as chiral ligands in metal based asymmetric catalysis and are used for various asymmetric transformations. Different compounds derived from sugars have also been used recently as organocatalysts for asymmetric synthesis. The present article provides some of the organocatalysts used for asymmetric synthesis.

Download Full-text

A Rapid and Sensitive Test for Diagnosing Heparin-Associated Thrombocytopenia

Thrombosis and Haemostasis ◽

10.1055/s-0038-1646493 ◽

1991 ◽

Vol 66 (06) ◽

pp. 734-736 ◽

Cited By ~ 256

Author(s):

A Greinacher ◽

I Michels ◽

V Kiefel ◽

C Mueller-Eckhardt

Keyword(s):

Molecular Weight ◽

Adverse Reactions ◽

Heparin Therapy ◽

Serotonin Release ◽

Low Molecular Weight ◽

Radioactive Tracers ◽

Sensitive Test ◽

Visual Evaluation ◽

Platelet Aggregometry ◽

Different Types

SummaryHeparin-associated thrombocytopenia (HAT) is a severe complication of heparin therapy. Its diagnosis is difficult. Conventional assays employ platelet aggregometry (PAA) and/or 14C-serotonin release (SRA) which are either insensitive (PAA) or require radioactive tracers (SRA). We here describe a newly developed sensitive and rapid assay based on visual evaluation of heparin-induced platelet activation (HIPA) in microtiter wells. Using sera of 34 patients with clinically suspected HAT we found the HIPA assay to be as sensitive as the SRA and superior to PAA. The HIPA assay allows investigation of crossreactivity with different types of heparins, low molecular weight (LMW) heparins and heparinoids. Three patients who required further parenteral anticoagulation and in whom the HIPA assay was negative before treatment with the LMW heparinoid Org 10172, were treated with this new heparinoid without adverse reactions. We conclude that the HIPA assay may be a useful tool for differential diagnosis and therapy in patients with HAT.

Download Full-text

Hydrolyzed Collagen—Sources and Applications

Molecules ◽

10.3390/molecules24224031 ◽

2019 ◽

Vol 24 (22) ◽

pp. 4031 ◽

Cited By ~ 17

Author(s):

Arely León-López ◽

Alejandro Morales-Peñaloza ◽

Víctor Manuel Martínez-Juárez ◽

Apolonio Vargas-Torres ◽

Dimitrios I. Zeugolis ◽

...

Keyword(s):

Molecular Weight ◽

Functional Activity ◽

Incubation Temperature ◽

Alkaline Media ◽

Low Molecular Weight ◽

Hydrolyzed Collagen ◽

Enzymatic Action ◽

Different Types ◽

Main Factors ◽

Different Sources

Hydrolyzed collagen (HC) is a group of peptides with low molecular weight (3–6 KDa) that can be obtained by enzymatic action in acid or alkaline media at a specific incubation temperature. HC can be extracted from different sources such as bovine or porcine. These sources have presented health limitations in the last years. Recently research has shown good properties of the HC found in skin, scale, and bones from marine sources. Type and source of extraction are the main factors that affect HC properties, such as molecular weight of the peptide chain, solubility, and functional activity. HC is widely used in several industries including food, pharmaceutical, cosmetic, biomedical, and leather industries. The present review presents the different types of HC, sources of extraction, and their applications as a biomaterial.

Download Full-text

In vitro Polymerisation of High and Low Molecular Weight Glutenin Subunits with Molecular Oxygen

Journal of Cereal Science ◽

10.1006/jcrs.2002.0497 ◽

2003 ◽

Vol 37 (2) ◽

pp. 223-229 ◽

Cited By ~ 3

Author(s):

I.M Verbruggen ◽

W.S Veraverbeke ◽

J.A Delcour

Keyword(s):

Molecular Weight ◽

Molecular Oxygen ◽

Low Molecular Weight ◽

Glutenin Subunits

Download Full-text

CONCENTRATION AND PURIFICATION OF THE PECTIN EXTRACTS BY ULTRAFILTRATION METHOD

Vestnik of the Russian agricultural science ◽

10.30850/vrsn/2018/2/45-48 ◽

2018 ◽

pp. 45-48

Author(s):

I. A. Ilina ◽

I. A. Machneva ◽

A. P. Chernutskiy

Keyword(s):

Heat Treatment ◽

Molecular Weight ◽

Comparative Analysis ◽

Raw Materials ◽

Low Molecular Weight ◽

Significant Deterioration ◽

High Productivity ◽

Different Types ◽

Stationary Cell

The work is devoted to the study of pectin extracts ultrafiltration using different types of membranes. Pectic extracts are the solutions of high molecular weight polysaccharides (MM from 15 to 50 kDa), which are destroyed in the process of heat treatment in the vacuum evaporating apparature, that leads to a significant deterioration in the quality of pectin. The impurity components in the pectin extract of a low molecular weight, which makes it possible to use ultrafiltration for both concentration and purification from ballast substances, that is very important. The objects of research were pectin extracts obtained from citrus raw materials; the membranes of the type UAM-100 and 200A were used as filter membranes. The results of the study have been shown, that the use of UAM-100 membranes in a stationary cell allows to remove up to 20% of the solution within 20 minutes, and with - stirring up to 27%. The use of membranes with large openings (up to 200 A) makes it possible to activate the process of the separation and concentration of pectin extracts: the degree of concentration reaches up 45%, the content of solids in the concentrate increases up to 7.6%, and the content of pectin to up 6.4%, that is in 1,7 times. However, the loss of low molecular weight pectin in the filtrate is about 4%. A comparative analysis of the results of research has shown a high productivity with the use of the capron membrane 200A, as well as on the qualitative parameters of the pectins, released from the concentrates, the higher parameters for the uroconid component, molecular weight, pectin jelly strength and complexing ability were noted for pectins isolated using the UAM- 100 membrane.

Download Full-text

Radioisomerization and Photoisomerization of Liquid 2 -Butenes in the Presence of Sulfur Compounds

Canadian Journal of Chemistry ◽

10.1139/v74-337 ◽

1974 ◽

Vol 52 (12) ◽

pp. 2337-2340 ◽

Cited By ~ 2

Author(s):

Guy J. Collin ◽

Patrick M. Perrin ◽

François X. Garneau

Keyword(s):

Molecular Weight ◽

Hydrogen Sulfide ◽

Liquid Phase ◽

Molecular Oxygen ◽

Carbon Disulfide ◽

Sulfur Hexafluoride ◽

The Other ◽

Isomerization Reaction ◽

Low Molecular Weight ◽

Cis And Trans

The liquid phase radiolysis and photolysis of cis- and trans-2-butenes were studied in the presence of various additives. A very efficient isomerization of 2-butenes was achieved by the addition of thiols of low molecular weight (hydrogen sulfide, methyl and isopropyl mercaptans). In the absence of molecular oxygen, we have observed G values (trans-2-butene) of the order of 90 000. On the other hand, little or no isomerization occurred in the presence of carbon disulfide, sulfur hexafluoride, and tert-dodecylmercaptan. Although the majority of the additives have no effect on the 2-butene:hydrogen sulfide system, conjugated diolefins block the isomerization reaction. These diolefins disappear from the reaction mixture.

Download Full-text

Degradation of Polyisoprene Networks by Oxygen

Rubber Chemistry and Technology ◽

10.5254/1.3542133 ◽

1960 ◽

Vol 33 (1) ◽

pp. 51-59 ◽

Cited By ~ 2

Author(s):

E. M. Bevilacqua

Keyword(s):

Molecular Weight ◽

Natural Rubber ◽

Present Report ◽

Hydrocarbon Chain ◽

Gas Absorption ◽

Oxygen Absorption ◽

Low Molecular Weight ◽

Oxidation Reactions ◽

Vulcanized Rubber ◽

Mechanism Of Oxidation

Abstract The insolubility of vulcanized rubber and the relatively low concentration at which oxidation reactions completely degrade the vulcanizate have made it necessary that indirect methods be used to study the reaction of molecular oxygen with rubber. The literature contains many reports of measurements of the absorption of oxygen by vulcanized rubber, which is easy and convenient experimentally. In some of these the rate of oxygen absorption has been the only property measured. This alone gives little information about the mechanism of oxidation, although the fact that the general form of curves of oxygen absorption as a function of time can be predicted by equations based on the known mechanism of oxidation of low molecular weight olefins is indirect support for similar mechanisms of oxidation of polymers. The technologically important reaction accompanying oxidation of natural rubber is scission, not detected by gas absorption measurements. It has been studied principally by determining the decay in stress of a sample at constant strain. The results suggest that scission occurs by a first order process at selected sites in the network. This has been interpreted to mean that crosslinks are the primary locus of oxidation in vulcanized rubber. Estimates of the amount of oxygen required for breaking a bond are available only for samples vulcanized with sulfur. From these it may be calculated that initially 4– 5 moles of oxygen is required per scission, when allowance is made for the effect of entanglements on stress. A marked difference between the relaxation of peroxide-cured and sulfur-cured samples has been reported. Horikx has made an extensive investigation of the solubility and swelling of oxidized vulcanized rubber. His results show that the hydrocarbon chain must be broken during oxidation. The mechanism of scission of unvulcanized rubber has been determined; in this work it was found that low molecular weight products are an important index of scission reactions. The present report describes preliminary work on the scission mechanism in vulcanized natural rubber which has two objectives; to repeat Horikx's experiments with vulcanizates incapable of further cure, and to determine whether low molecular weight products accompany the scission reaction.

Download Full-text

Polymer bound pyrrole compounds, IX. Photophysical and singlet molecular oxygen photosensitizing properties of mesoporphyrin IX covalently bound to a low molecular weight polyethylene glycol

Journal of Photochemistry and Photobiology B Biology ◽

10.1016/s1011-1344(97)00080-8 ◽

1997 ◽

Vol 41 (1-2) ◽

pp. 53-59 ◽

Cited By ~ 11

Author(s):

Pilar Abós ◽

Carme Artigas ◽

Sonia Bertolotti ◽

Silvia E. Braslavsky ◽

Pere Fors ◽

...

Keyword(s):

Molecular Weight ◽

Polyethylene Glycol ◽

Molecular Oxygen ◽

Low Molecular Weight ◽

Singlet Molecular Oxygen ◽

Covalently Bound

Download Full-text

Aerobic Epoxidation of Low-Molecular-Weight and Polymeric Olefins by a Supramolecular Manganese Porphyrin Catalyst

Catalysts ◽

10.3390/catal9020195 ◽

2019 ◽

Vol 9 (2) ◽

pp. 195 ◽

Cited By ~ 11

Author(s):

Ivan Bernar ◽

Floris Rutjes ◽

Johannes Elemans ◽

Roeland Nolte

Keyword(s):

Molecular Weight ◽

Ambient Temperature ◽

High Activity ◽

Molecular Oxygen ◽

Low Molecular Weight ◽

Mechanistic Studies ◽

Manganese Porphyrin ◽

Reaction Conditions ◽

Porphyrin Complex ◽

Epoxidation Reaction

We report on the highly efficient epoxidation of low-molecular-weight and polymeric olefins catalyzed by a supramolecular manganese porphyrin complex using molecular oxygen as an oxidant and an aldehyde as a co-reductant. At ambient temperature and under optimized reaction conditions, the catalyst showed high activity and stereoselectivity. The efficiency of the supramolecular manganese porphyrin was higher than that of a reference porphyrin catalyst, possibly because it was more stable under the applied reaction conditions. Mechanistic studies suggest that a manganese oxo porphyrin complex may be an intermediate in the epoxidation reaction.

Download Full-text