scholarly journals Extraction of Lignins Using a Modified Dioxane Method and an Ionic Liquid and Comparative Molecular Weight and Structural Studies by Chromatography and ??C NMR Spectroscopy, Techniques

2014 ◽  
Vol 2 (5) ◽  
pp. 36 ◽  
Author(s):  
Mahnaz Oghbaie
Keyword(s):  
Molecular Weight ◽  
Ionic Liquid ◽  
Nmr Spectroscopy ◽  
Structural Studies ◽  
C Nmr

Structural studies of digitoxin and related cardenolides by two-dimensional NMR

1990 ◽  
Vol 68 (2) ◽  
pp. 272-277 ◽  
Author(s):  
Torbjörn Drakenberg ◽  
Peter Brodelius ◽  
Deane D. McIntyre ◽  
Hans J Vogel
Keyword(s):  
Nmr Spectroscopy ◽  
Nmr Spectra ◽  
Chair Conformation ◽  
Coupling Constants ◽  
Two Dimensional ◽  
Structural Studies ◽  
Solution Conformation ◽  
Phase Sensitive ◽  
Multiple Relay ◽  
C Nmr

The 1H and 13C NMR spectra of the cardenolides digitoxigenin, digoxigenin, digitoxin, and mono- and bis-digitoxigenin digitoxosides have been completely assigned by two-dimensional NMR spectroscopy. The techniques used include phase-sensitive COSY, multiple relay COSY, and carbon–proton correlation (HETCOR and HMQC) spectra. Various aspects of the solution conformation of the steroid moiety of digitoxin and digoxigenin could be determined from coupling constants and NOE difference experiments and they are indicative of an all-chair conformation. The carbohydrate rings in digitoxin and the mono- and bis-digitoxigenin digitoxosides are also in the chair conformation. Keywords: cardenolides, digitoxigenin, digitoxin, 2-dimensional NMR, conformational analysis.

Synthesis, spectroscopic characterization, and structural studies of organogermanium tri- and monothiocarbonates. Crystal structures of Me2Ge[S2CSEt]2, Ph3Ge[SCO2Me], Ph3Ge[SCO2(i-Pr)], and Ph2Ge[SCO2Me]2

1998 ◽  
Vol 76 (3) ◽  
pp. 319-334 ◽  
Author(s):  
John E Drake ◽  
Jincai Yang
Keyword(s):  
Mass Spectrometry ◽  
Nmr Spectroscopy ◽  
Crystal Structures ◽  
Sodium Salt ◽  
Variable Temperature ◽  
Spectroscopic Characterization ◽  
Structural Studies ◽  
Cell Parameters ◽  
Derivatives Of ◽  
C Nmr

Two series of S-alkyl trithiocarbonate derivatives of imethylgermane, Me2Ge[S2CSR]2, and halodiphenylgermane, Ph2GeX[S2CSR], where R = Me, i-Pr, n-Pr, n-Bu and X = Cl, Br, and three series of O-alkyl monothiocarbonate derivatives of triphenylgermane, Ph3Ge[SCO2R], diphenylgermane, Ph2Ge[SCO2R], and trimethylgermane, me3Ge[SCO2R], where R = Me, i-Pr, and n-Pr, have been prepared in 73-92% yields by the reaction of the potassium or sodium salt of the appropriate tri- or monothiocarbonic acid with dichlorodimethyl-, chlorotriphenyl-, dichlorodiphenyl-, and chlorotrimethylgermane. The compounds were principally characterized by infrared, Raman, and 1H and 13C NMR spectroscopy, including some variable temperature studies, as well as by mass spectrometry. Me2Ge[S2CSEt]2, 1: P21/m (No. 11) with cell parameters a = 6.647(4) Å, b = 7.423(2) Å, c = 16.290(4) Å, β = 91.07(3)°, V = 803.6(4) Å3, Z = 2, R = 0.0484,Rw = 0.0485. Ph3Ge[SCO2Me],13: P1bar (No. 2) with cell parameters a = 9.970(4) Å, b = 10.660(3) Å, c = 9.853(2) Å, α = 101.78(2)°, β = 109.98(2)°, γ = 89.76(3)°, V = 961.0(5) Å3, Z = 2, R = 0.0534, Rw = 0.0451. Ph3Ge[SCO2(i-Pr)], 14: P 1bar (No. 2) with cell parameters a = 14.386(7) Å, b = 18.598(6) Å, c = 9.223(3) Å, α = 102.85(3)°, β = 94.58(3)°, γ = 108.13(3)°, V = 2256(1) Å3, Z = 2, R = 0.0545, Rw = 0.0552. Ph2Ge[SCO2Me]2, 16: Cc, (No. 9) with cell parameters a = 11.790(4) Å, b = 13.696(5) Å, c = 23.232(6) Å, β = 92.26(3)°, V = 3748(2) Å3, Z = 8, R = 0.0563, Rw = 0.0512. The immediate environment about Ge is that of tetrahedral but the orientations of the thiocarbonate groups display interesting features.Key words: structure, germanium, phenyl, methyl, thiocarbonates.

Functional Modification of Xylan-Rich Hemicelluloses in Ionic Liquid

2011 ◽  
Vol 391-392 ◽  
pp. 950-954 ◽  
Author(s):  
Xin Wen Peng ◽  
Jun Li Ren ◽  
Lin Xin Zhong ◽  
Yan Bo Huang ◽  
Run Cang Sun
Keyword(s):  
Thermal Stability ◽  
Thermal Analysis ◽  
Ionic Liquid ◽  
Differential Thermal Analysis ◽  
Nmr Spectroscopy ◽  
Thermal Behavior ◽  
Succinic Anhydride ◽  
Different Temperatures ◽  
Thermal Stability Of ◽  
C Nmr

Xylan-rich Hemicelluloses (XH) isolated from wheat straw were converted to functional biopolymers by modification using succinic anhydride (SA) as reactant without catalyst in 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) ionic liquid. The reaction was performed under various conditions such as different temperatures, different times, and the different amounts of SA, and the effect of reaction factors on the degree substitution (DS) of products were discussed. The product had the maximum DS of 1.80. The structure of modified hemicellulosic derivatives (MD) was actually confirmed by13C NMR spectroscopy. The thermal behavior of MD was monitored by means of thermogravimetry (TG) and differential thermal analysis (DTA), and the thermal stability of MD was lower than XH.

The heterogeneity of two Canadian kraft lignins

1995 ◽  
Vol 73 (5) ◽  
pp. 629-634 ◽  
Author(s):  
R.W. Thring ◽  
S.L. Griffin
Keyword(s):  
Carbon Dioxide ◽  
Molecular Weight ◽  
Nmr Spectroscopy ◽  
High Molecular Weight ◽  
Sulphuric Acid ◽  
Weight Fraction ◽  
Kraft Lignin ◽  
The Other ◽  
High Molecular Weight Fraction ◽  
C Nmr

Two kraft lignins, one precipitated with carbon dioxide and the other with sulphuric acid, have been fractionated into three distinct fractions by sequential extraction using organic solvents of increasing hydrogen-bonding capacity. The lignins and fractions were comparatively characterized in terms of yield, methoxyl group content, molecular weight distribution, and 13C NMR spectroscopy. For a given lignin, the fractions showed differences in yield, composition, and chemical structure. A significant portion (21%) of the carbon dioxide precipitated kraft lignin is composed of ethyl acetate soluble material of low molecular weight. This fraction, which is richer in guaiacyl moieties than the other fractions, is virtually absent in the sulphuric acid precipitated kraft lignin. The occurrence of "tails" in the high molecular weight fraction, especially from the carbon dioxide precipitated kraft lignin, suggests the presence of material of very high molecular weight. Data from 13C NMR spectroscopy does little to elucidate the nature or origin of the material causing these tails. Keywords: kraft lignins, heterogeneity, fractionation, characterization.

Structural Studies on Ionic Liquid/Water/Peptide Systems by HR-MAS NMR Spectroscopy

ChemPhysChem ◽  
2012 ◽  
Vol 13 (7) ◽  
pp. 1836-1844 ◽  
Author(s):  
Carmen Mrestani-Klaus ◽  
Annekathrin Richardt ◽  
Christian Wespe ◽  
Annegret Stark ◽  
Eberhard Humpfer ◽  
...  
Keyword(s):  
Ionic Liquid ◽  
Nmr Spectroscopy ◽  
Liquid Water ◽  
Mas Nmr ◽  
Structural Studies

Fractionation of woodmeal by prehydrolysis and thermal organosolv. Alkaline depolymerization, chemical functionality, and molecular weight distribution of recovered lignins and their fractions

1993 ◽  
Vol 71 (6) ◽  
pp. 779-789 ◽  
Author(s):  
Ronald W. Thring ◽  
Esteban Chornet ◽  
Ralph P. Overend
Keyword(s):  
Molecular Weight ◽  
Solvent Extraction ◽  
Phenolic Compounds ◽  
Nmr Spectroscopy ◽  
Elemental Composition ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Side Chain ◽  
Molecular Weight Fractions ◽  
C Nmr

Thermal organosolv glycol lignins and their fractions have been characterized by means of elemental composition, molecular weight distribution, and 1H and 13C NMR spectroscopy. Fractionation of each lignin by sequential solvent extraction produced fractions of increasing molecular weight and polydispersity. Structures in the highest molecular weight fractions were found to be linked by a high proportion of β-O-4 type bonds, whilst the lowest molecular weight fractions consisted of a high content of saturated aliphatic side-chain structures. A noticeable difference in the content of carbohydrate contaminants in both starting lignins indicated the formation of relatively stable lignin–carbohydrate complexes, especially in the lignin recovered from pretreated wood. In addition, depolymerization of the lignins and their fractions to monomeric compounds was explored using alkaline hydrolytic and nitrobenzene oxidative routes. The highest molecular weight fractions from each lignin were identified as the best candidates for production of useful monomeric phenolic compounds.

scholarly journals Synthesis and Characterization of Acrylamide-Based Anionic Copolymer and Investigation of Solution Properties

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
H. Jamshidi ◽  
A. Rabiee
Keyword(s):  
Molecular Weight ◽  
Nmr Spectroscopy ◽  
Solution Viscosity ◽  
Feed Ratio ◽  
Reaction Conditions ◽  
Aqueous Sodium Chloride Solution ◽  
Shear Rates ◽  
High Molecular Weight Product ◽  
C Nmr

The copolymer of acrylamide (AM) and 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS) was synthesized through radical solution polymerization by potassium persulfate as initiator. By changing the AMPS feed ratio from 10 to 70%, and keeping other reaction conditions constant, different copolymers were synthesized. The techniques of Fourier transform infrared (FTIR) and nuclear magnetic resonance (1H-13C-NMR) spectroscopy were used for identification of functional groups and confirmation of copolymers’ structure. Intrinsic and apparent viscosity of samples were measured in aqueous sodium chloride solution under standard conditions. The anionic degree of copolymers was determined by back titration method and by13C-NMR spectroscopy. Molecular weight of copolymers was determined by the Mark-Houwink relationship. The measured molecular weight of samples showed that we have acquired a high molecular weight product. The effect of different range of shear rates on solution viscosity was evaluated. The copolymer solutions showed non-Newtonian shear thinning behavior. The performance of copolymers with respect to shear resistance and molecular weight was evaluated from industry application standpoint.

The mechanism of formation of 2,7-dimethyl-2,6-octadiene in the synthesis of 3-methylene-7-methyl-1,6-octadiene

1983 ◽  
Vol 48 (7) ◽  
pp. 1864-1866
Author(s):  
Jan Bartoň ◽  
Ivan Kmínek
Keyword(s):  
Mass Spectrometry ◽  
Nmr Spectroscopy ◽  
Alkali Metal ◽  
Chromatographic Analysis ◽  
Solid Phase ◽  
Reaction Pathway ◽  
Mechanism Of Formation ◽  
Gas Chromatographic Analysis ◽  
C Nmr ◽  
Visual Observations

2,7-Dimethyl-2,6-octadiene is formed in the catalytic solution for the dimerization of 2-methyl-1,3-butadiene to β-myrcene (3-methylene-7-methyl-1,6-octadiene), as revealed by mass spectrometry and 13C NMR spectroscopy. Visual observations together with the results of gas chromatographic analysis of the catalytic solution suggest that the formation of 2,7-dimethyl-2,6-octadiene is associated with the transition of the alkali metal (sodium) from the solid phase into the solution. A reaction pathway is suggested accounting for the formation of 2,7-dimethyl-2,6-octadiene in the system.

Non-cyclol (lactame) ergot alkaloids

1982 ◽  
Vol 47 (12) ◽  
pp. 3312-3317 ◽  
Author(s):  
Josef Stuchlík ◽  
Alois Krajíček ◽  
Ladislav Cvak ◽  
Jiří Spáčil ◽  
Petr Sedmera ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Ergot Alkaloids ◽  
C Nmr

Two new alkaloids were isolated from the field ergot. Their structures, N-(D-lysergyl-L-valyl)cyclo(L-valyl-D-prolyl) (IV) and N-(D-lysergyl-L-valyl)cyclo(L-leucyl-D-prolyl) (V), were assigned by mass, 1H and 13C NMR spectroscopy.

An unusual reaction of a bridged triterpenoid α-diketone with acetic anhydride

1991 ◽  
Vol 56 (12) ◽  
pp. 2917-2935 ◽  
Author(s):  
Eva Klinotová ◽  
Václav Křeček ◽  
Jiří Klinot ◽  
Miloš Buděšínský ◽  
Jaroslav Podlaha ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Nmr Spectroscopy ◽  
Acetic Anhydride ◽  
Spectral Methods ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mild Conditions ◽  
Condensation Products ◽  
Unsaturated Lactones ◽  
C Nmr

3β-Acetoxy-21,22-dioxo-18α,19βH-ursan-28,20β-olide (IIIa) reacts with acetic anhydride in pyridine under very mild conditions affording β-lactone IVa and γ-lactones Va and VIIa as condensation products. On reaction with pyridine, lactones Va and VIIa undergo elimination of acetic acid to give unsaturated lactones VIIIa and IXa, respectively. Similarly, the condensation of 20β,28-epoxy-21,22-dioxo-18α,19βH-ursan-3β-yl acetate (IIIb) with acetic anhydride leads to β-lactone IVb and γ-lactone Vb; the latter on heating with pyridine affords unsaturated lactone VIIIb and 21-methylene-22-ketone Xb. The structure of the obtained compounds was derived using spectral methods, particularly 1H and 13C NMR spectroscopy; structure of lactone IVa was confirmed by X-ray diffraction.

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