Comparative Studies of Brown Coal and Lignin. I. Infra-Red Spectra

1960 ◽  
Vol 13 (1) ◽  
pp. 156 ◽  
Author(s):  
RA Durie ◽  
BM Lynch ◽  
S Sternhell
Keyword(s):  
Brown Coal ◽  
Hydriodic Acid ◽  
Conclusive Evidence ◽  
Hydroxyl Groups ◽  
Infra Red ◽  
Aliphatic Ether ◽  
Derivatives Of ◽  
Alcoholic Hydroxyl ◽  
Chemical Evidence

The infra-red spectra of two softwood lignins are discussed with reference to the spectra of their acetyl and methoxyl derivatives. The spectra of the respective acetyl derivatives provide conclusive evidence for the presence of both phenolic and alcoholic groups in lignin and oxidized lignin, and of alcoholic groups only in the methoxyl derivatives of both these samples. Treatment of lignin with hydriodic acid in the conventional Zeisel determination of methoxyl groups eliminates the alcoholic hydroxyl groups and appears to split aliphatic ether linkages. The spectrum of lignin treated with hydriodic acid is very similar to that of brown coal, which supports previous chemical evidence that brown coal appears to be essentially " demethylated dehydrated lignin ". The progress of the isolation of lignin from wood was followed by infra-red spectroscopy.

Aminoglycoside antibiotics: The formation and characterization of dihydrooxazine derivatives in the paromomycin series

1978 ◽  
Vol 56 (11) ◽  
pp. 1492-1499 ◽  
Author(s):  
Stephen Hanessian ◽  
Robert Massé ◽  
Goran Ekborg
Keyword(s):  
Chemical Modification ◽  
Zinc Chloride ◽  
Aminoglycoside Antibiotics ◽  
High Yield ◽  
Hydroxyl Groups ◽  
Model Studies ◽  
Derivatives Of ◽  
Excess Zinc ◽  
Chemical Evidence

Treatment of penta-N-benzyloxycarbonylparomomycin with benzaldehyde and excess zinc chloride gives a dibenzylidene derivative in high yield. This consists of the 4′,6′-O-benzylidene 4′′′,6′′′-N,O-benzylidene (dihydrooxazine) derivative of penta-N-benzyloxycarbonylparomomycin. Chemical evidence is presented to support this structure and model studies are reported for the formation of dihydrooxazine and oxazolidine derivatives of benzyloxycarbonylamino sugars containing suitably situated hydroxyl groups. The easily obtained dihydrooxazine derivative of paromomycin constitutes an interesting, preferentially blocked derivative, that is useful for the chemical modification of the parent antibiotic.

The role of secondary alcoholic groups of D-galacturonan in its degradation with exo-D-galacturonanase

1980 ◽  
Vol 45 (2) ◽  
pp. 427-434 ◽  
Author(s):  
Kveta Heinrichová ◽  
Rudolf Kohn
Keyword(s):  
Acetyl Derivative ◽  
Competitive Inhibitor ◽  
Hydroxyl Groups ◽  
Pectic Acid ◽  
Substrate Complex ◽  
Enzyme Substrate ◽  
The Individual ◽  
Degradation Degree ◽  
Derivatives Of

The effect of exo-D-galacturonanase from carrot on O-acetyl derivatives of pectic acid of variousacetylation degree was studied. Substitution of hydroxyl groups at C(2) and C(3) of D-galactopyranuronic acid units influences the initial rate of degradation, degree of degradation and its maximum rate, the differences being found also in the time of limit degradations of the individual O-acetyl derivatives. Value of the apparent Michaelis constant increases with increase of substitution and value of Vmax changes. O-Acetyl derivatives act as a competitive inhibitor of degradation of D-galacturonan. The extent of the inhibition effect depends on the degree of substitution. The only product of enzymic reaction is D-galactopyranuronic acid, what indicates that no degradation of the terminal substituted unit of O-acetyl derivative of pectic acid takes place. Substitution of hydroxyl groups influences the affinity of the enzyme towards the modified substrate. The results let us presume that hydroxyl groups at C(2) and C(3) of galacturonic unit of pectic acid are essential for formation of the enzyme-substrate complex.

Spectrophotometric study of the complexation equilibria of cadmium ions with 5-bromo and 5-chloro derivatives of 2-(2-pyridylazo)-5-diethylaminophenol (BrPADAP, ClPADAP)

1983 ◽  
Vol 48 (1) ◽  
pp. 52-59 ◽  
Author(s):  
Vlastimil Kubáň ◽  
Miroslav Macka
Keyword(s):  
Equilibrium Constants ◽  
Spectrophotometric Study ◽  
Graphical Analysis ◽  
Optimal Conditions ◽  
Cadmium Ions ◽  
Brij 35 ◽  
Ethanol Medium ◽  
Triton X ◽  
Derivatives Of

The composition, optical characteristics, molar absorption coefficients and equilibrium constants of the reactions of formation of the ML and ML2 complexes of both reagents with cadmium(II) ions were determined by graphical analysis and numerical interpretation of the absorbance-pH curves by the modified SQUAD-G program. Optimal conditions were proposed for the spectrophotometric determination of Cd in 10% v/v ethanol medium in the presence of 0.1% w/v Triton X-100 or 1% w/v Brij 35. BrPADAP and ClPADAP are the most sensitive spectrophotometric reagents for the determination of cadmium(II) ions (ε = 1.28-1.44 . 105 mmol-1 cm2 at 560 nm and pH 8.0-9.5) with a high colour contrast in the reaction (Δλmax ~117 nm) and a selectivity similar to that of other N-heterocyclic azodyes (PAR, PAN, etc.).

Spectrophotometric study of the acid-base and optical properties of the 5-bromo and 5-chloro derivatives of 2-(2-pyridylazo)-5-(diethylamino)phenol (BrPADAP, ClPADAP) and their complexation equilibria with zinc(II) ions

1982 ◽  
Vol 47 (10) ◽  
pp. 2676-2691 ◽  
Author(s):  
Miroslav Macka ◽  
Vlastimil Kubáň
Keyword(s):  
Equilibrium Constants ◽  
Spectrophotometric Study ◽  
Graphical Analysis ◽  
Alkaline Media ◽  
Acid Base ◽  
Ethanol Medium ◽  
Triton X ◽  
Mixed Water ◽  
Derivatives Of

The optical and acid-base characteristics of BrPADAP and ClPADAP were studied in mixed water-ethanol and water-DMF media and in 10% ethanol medium in the presence of cationic, anionic and nonionic tensides. The composition, optical characteristics, molar absorption coefficients and equilibrium constants of the ML and ML2 complexes with zinc(II) ions were found by graphical analysis and numerical interpretation of the absorbance curves by the modified SQUAD-G program. Optimal conditions were found for the spectrophotometric determination of Zn(II) in the presence of 0.1% Triton X-100 or 1% Brij 35 in alkaline media with pH = 6.5-10. BrPADAP and ClPADAP are the most sensitive reagents (ε = 1.3-1.6 . 105 mmol-1 cm2 at 557 and 560 nm, respectively) for the determination of zinc with high colour contrast of the reaction (Δλ = 104 nm) and selectivity similar to that for the other N-heterocyclic azodyes (PAN, PAR, etc.).

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