Lignin and related compounds. VI. A study of variables affecting the hydrogenolysis of spruce wood lignin using a rhodium-on-charcoal catalyst

The effect of reaction conditions on the hydrogenolysis of spruce wood lignin over a rhodium-on-charcoal catalyst has been studied and monitored by the yields of the three major degradation products, 1, 2, and 5. Variables included: initial pressure of hydrogen, amount of catalyst, and acidity–basicity of the media. Little variation occurred under moderate acidic or basic conditions with yields of 18–20% of lignin recovered as monomers. Under strongly acidic or basic conditions both yields and relative abundances changed appreciably. Initial hydrogen pressures less than 500 psig resulted in slightly decreased yields in some cases. In strongly alkaline media similar results were obtained with or without added hydrogen provided the catalyst were present.

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Lignin and related compounds. VIII. Lignin monomers and dimers from hydrogenolysis of aspen poplar wood using rhodium-on-charcoal catalyst

Canadian Journal of Chemistry ◽

10.1139/v81-152 ◽

1981 ◽

Vol 59 (7) ◽

pp. 1028-1031 ◽

Cited By ~ 16

Author(s):

Kenichi Sudo ◽

Donald J. Mullord ◽

James M. Pepper

Keyword(s):

Silica Gel ◽

Lignin Degradation ◽

Degradation Products ◽

Initial Pressure ◽

Hydroxybenzoic Acid ◽

Poplar Wood ◽

Catalytic Hydrogenolysis ◽

Lignin Degradation Products ◽

Related Compounds ◽

Soluble Lignin

Aspen poplar wood meal has been subjected to catalytic hydrogenolysis in dioxane–water (9:1) at 500 psig initial pressure of hydrogen over a 5% rhodium-on-charcoal catalyst for five hours at 195 + 5 °C. The resulting chloroform-soluble lignin degradation products were separated by cellulose and silica gel column chromatography. The following compounds were isolated and identified: 4-hydroxybenzoic acid (5), 1-(4-hydroxy-3,5-dimethoxyphenyl)-1-propanone (propiosyringone) (6), 2,2′-dihydroxy-3,3′-dimethoxy-5,5′-dipropylbiphenyl (7), 2,3-bis(4-hydroxy-3,5-dimethoxyphenyl)-1-propanol (11), and a mixture of 3-(4-hydroxy-3,5-dimethoxyphenyl)-2-(4-hydroxy-3-methoxyphenyl)-1-propanol (9) and 3-(4-hydroxy-3-methoxyphenyl)-2-(4-hydroxy-3,5-dimethoxyphenyl)-1-propanol (10).

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The nature of active centers catalyzing oxygen electro-reduction at platinum surfaces in alkaline media

Energy & Environmental Science ◽

10.1039/c8ee03228a ◽

2019 ◽

Vol 12 (1) ◽

pp. 351-357 ◽

Cited By ~ 11

Author(s):

Yunchang Liang ◽

David McLaughlin ◽

Christoph Csoklich ◽

Oliver Schneider ◽

Aliaksandr S. Bandarenka

Keyword(s):

Scanning Tunneling Microscopy ◽

Alkaline Media ◽

Scanning Tunneling ◽

Tunneling Microscopy ◽

Active Centers ◽

Reaction Conditions ◽

Electrochemical Scanning Tunneling Microscopy ◽

Platinum Surfaces ◽

Alkaline Electrolytes ◽

Noise Measurements

The recently introduced electrochemical scanning tunneling microscopy noise measurements were applied to directly identify active centers for oxygen electro-reduction at Pt-based surfaces in three alkaline electrolytes under reaction conditions.

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ChemInform Abstract: STUDIES ON THE AUTOXIDATION OF TERT-BUTYL-SUBSTITUTED PHENOLS IN ALKALINE MEDIA. 2. REACTIONS OF 4,6-DI-TERT-BUTYLGUAIACOL AND RELATED COMPOUNDS

Chemischer Informationsdienst ◽

10.1002/chin.197802119 ◽

1978 ◽

Vol 9 (2) ◽

Author(s):

J. GIERER ◽

F. IMSGARD

Keyword(s):

Alkaline Media ◽

Substituted Phenols ◽

Tert Butyl ◽

Related Compounds

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Factors Influencing The Structure Of Terminal Plasmin Degradation Products Of Human Fibrinogen And Fibrin

10.1055/s-0038-1653181 ◽

1981 ◽

Author(s):

W Nieuwenhuizen ◽

A Vermond ◽

F Haverkate

Keyword(s):

Protective Effect ◽

Calcium Ions ◽

Degradation Products ◽

Iminodiacetic Acid ◽

Human Fibrinogen ◽

Factors Influencing ◽

Separate Effect ◽

The Media ◽

Carboxy Terminal ◽

D Dimer

Experiments have been carried out with fibrinogen and with purified degradation products of fibrinogen and fibrin which demonstrate that the structure of D fragments obtained after prolonged plasmin digestion is influenced by several factors in the media.The previously described protective effect of calcium ions on the γ-chain carboxy-terminals of fibrinogen against plasmin attack is rather independent of the composition of the media (e.g., also observed in 2 M urea and/or high plasmin activities).Several compounds such as EDTA, EGTA, citrate and iminodiacetic acid appear to have a separate effect, which is best observed at low plasmin concentrations and in the absence of Ca2+ . Under these conditions, these compounds appear to make the γ-chain carboxy-terminal ends of the D- and D-dimer fragments more susceptible to plasmin digestion.Finally, as demonstrated by experiments with purified D;E complexes from fibrinogen and with whole fibrinogen digests, the E-moiety of the D:E complexes appears to be capable of protecting the D-moiety against low plasmin concentrations also in the absence of calcium ions.

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Separation and Quantitation of Alkylphosphocholines and Analogues of Different Liposome Formulations by HPTLC

Journal of AOAC International ◽

10.1093/jaoac/84.4.1277 ◽

2001 ◽

Vol 84 (4) ◽

pp. 1277-1282 ◽

Cited By ~ 3

Author(s):

Hannelore Ratz ◽

Horst Schnell ◽

Matthias Rischer ◽

Hans-Jörg Eibl

Keyword(s):

Quality Control ◽

Oral Administration ◽

Thin Layer ◽

High Performance ◽

Degradation Products ◽

Cytostatic Activity ◽

Chromatographic System ◽

Liposomal Formulations ◽

Mobile Phases ◽

Related Compounds

Abstract High-performance thin-layer chromatographic (HPTLC) analysis of non UV-active phospholipids in biological matrixes is a common method for separation, detection, and quantitation. Liposomes containing new alkylphosphocholines and analogues with enhanced cytostatic activity had been prepared. The liposomal formulations were designed to enable the intravenous application of the alkylphosphocholines and analogues and to reduce dose-limiting toxicities observed after oral administration. For quality control the liposomes were analyzed by HPTLC for content of 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol (DPPG), cholesterol, alkylphosphocholines, and analogues and their related compounds (main degradation products). Due to the differences in lipophily of the compounds, different mobile phases were necessary to achieve separation. Automated Multiple Development was used to reduce the number of plates and to improve the selectivity and the capacity of the chromatographic system to separate the described alkylphosphocholines and analogues from DPPG and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine in one chromatographic system.

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Enterolactone and Other Lignan Metabolites as Taxon-Specifi c Markers in Modern and Ancient Woodrat Middens

Zeitschrift für Naturforschung C ◽

10.1515/znc-2013-7-811 ◽

2013 ◽

Vol 68 (7-8) ◽

pp. 327-335

Author(s):

David A. Zinniker ◽

Camille A. Holmgren ◽

Bernd R. T. Simoneit

Keyword(s):

Natural Products ◽

Microbial Communities ◽

Degradation Products ◽

Nordihydroguaiaretic Acid ◽

Structural Elements ◽

Creosote Bush ◽

Higher Plant ◽

Plant Source ◽

Related Compounds ◽

Plant Lignans

Diversely sourced degradation products of higher plant lignans were identifi ed in modern and ancient woodrat (Neotoma) middens. The markers indicate extensive chemical modifi cation by intestinal microbial communities of mammals. The observed defunctionalized phenols represent a group of natural products, and their structural elements reveal information about the plant source. The phenols are derived mainly from two precursor types: (1) enterolactone and derivatives from conifer lignans, and (2) 2,3-bis(3’-hydroxybenzyl)butane and related compounds from lignans such as nordihydroguaiaretic acid common in Larrea sp. (e.g. creosote bush)

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Advances in Chemistry of Isothiocyanate-derived Colourants

Czech Journal of Food Sciences ◽

10.17221/1092-cjfs ◽

2009 ◽

Vol 27 (Special Issue 1) ◽

pp. S207-S210

Author(s):

K. Cejpek ◽

J. Velíšek

Keyword(s):

Amino Acids ◽

Essential Oils ◽

Maillard Reaction ◽

Heterogeneous Group ◽

Model Systems ◽

Alkaline Media ◽

Reaction Conditions ◽

Condensation Products ◽

Amino Compounds ◽

Methylene Group

This study is focused on the reactions of isothiocyanates (ITCs) in the presence of amino compounds leading to coloured structures <I>via</I> substituted 2-thiohydantoins. A series of complementary experiments has been done and appropriate reaction conditions and structural prerequisites have been defined. Low-molecular colourants isolated and characterised from the model systems can be sorted into three groups. Yellow to red diastereomeric dehydrodimers of 2-thiohydantoin derivatives that contain an acidic methylene group are formed in mixtures consisted of ITCs and amino acids with α-methylene group in mild acidic to mild alkaline systems. The condensation products of the 2-thiohydantoins with reactive aromatic or heterocyclic carbaldehydes from the Maillard reaction, essential oils etc. comprise a heterogeneous group of mostly yellow colourants. Blue compounds of two types are structurally more complicated structures that arise from <I>N</I>-substituted amino acids and ITCs in alkaline media.

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Electrochemical Reduction of Quinones in Different Media: A Review

International Journal of Electrochemistry ◽

10.4061/2011/816202 ◽

2011 ◽

Vol 2011 ◽

pp. 1-22 ◽

Cited By ~ 204

Author(s):

Partha Sarathi Guin ◽

Saurabh Das ◽

P. C. Mandal

Keyword(s):

Electron Flow ◽

Biological Systems ◽

Ion Pair ◽

Pair Formation ◽

Transfer Reactions ◽

Intermolecular Hydrogen Bonding ◽

Reaction Conditions ◽

Photosynthetic Electron Flow ◽

The Media ◽

As Toxicity

The electron transfer reactions involving quinones, hydroquinones, and catechols are very important in many areas of chemistry, especially in biological systems. The therapeutic efficiency as well as toxicity of anthracycline anticancer drugs, a class of anthraquinones, is governed by their electrochemical properties. Other quinones serve as important functional moiety in various biological systems like electron-proton carriers in the respiratory chain and their involvement in photosynthetic electron flow systems. The present paper summarizes literatures on the reduction of quinones in different solvents under various conditions using different electrochemical methods. The influence of different reaction conditions including pH of the media, nature of supporting electrolytes, nature of other additives, intramolecular or intermolecular hydrogen bonding, ion pair formation, polarity of the solvents, stabilization of the semiquinone and quinone dianion, catalytic property, and adsorption at the electrode surface, are discussed and relationships between reaction conditions and products formed have been presented.

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