Reactions of lignin model compounds with pulp bleaching chemicals. Cannizzaro-type reaction of tetrachloro-o-benzoquinone with alkali

1992 ◽  
Vol 70 (6) ◽  
pp. 1706-1710 ◽  
Author(s):  
A. Bruce McKague ◽  
Douglas W. Reeve ◽  
Steven J. Rettig ◽  
James Trotter
Keyword(s):  
Direct Methods ◽  
Aqueous Sodium Hydroxide ◽  
Pulp Bleaching ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Full Matrix ◽  
Aqueous Sodium ◽  
X Ray ◽  
X Ray Crystallography ◽  
Lignin Model

Reaction of tetrachloro-o-benzoquinone 1 with aqueous sodium hydroxide resulted in a Cannizzaro-type disproportionation into tetrachloromuconic acid and tetrachlorocatechol. The tetrachloromuconic acid was isolated and identified by X-ray crystallography as the methyl ester of the cyclized lactone 3. Crystals of C7H3Cl3O4, 4, are orthorhombic, a = 9.991 (2), b = 7.981 (1), c = 24.626(2) Å, Z = 8, space group Pna21. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to R = 0.033 for 1609 reflections with I ≥ 3σ(I).

Reactions of lignin model compounds with pulp bleaching chemicals. Reactions of 4-methyltrichlorocatechol

1992 ◽  
Vol 70 (6) ◽  
pp. 1711-1716 ◽  
Author(s):  
A. Bruce McKague ◽  
Douglas W. Reeve ◽  
Steven J. Rettig ◽  
James Trotter
Keyword(s):  
Direct Methods ◽  
Aqueous Sodium Hydroxide ◽  
Pulp Bleaching ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Full Matrix ◽  
Aqueous Sodium ◽  
Space Group ◽  
Lignin Model ◽  
Benzilic Acid

Aqueous chlorination of 4-methyltrichlorocatechol 2 gave the tetrachlorohydroxycyclohexenone 4, which crystallized as the hydrate 5. Reaction of 4 with aqueous sodium hydroxide resulted in a benzilic acid rearrangement to the tetrachlorodihydroxycyclopentenecarboxylic acid 6. These reactions have important implications with respect to understanding how lignin is removed during pulp bleaching. Crystals of the tetrachlorotrihydroxycyclohexenone 5 are monoclinic, a = 11.4420(6), b = 7.5873(9), c = 12.6443(6) Å, β = 101.266(4)°, Z = 4, space group P21/c, and those of the methyl tetrachlorodihydroxycyclopentenecarboxylate 7 are monoclinic, a = 28.447(1), b = 6.929(1), c = 12.597(1) Å, β = 103.074(5)°, Z = 8, space group C2/c. The structures were solved by direct methods and were refined by full-matrix least-squares procedures to R = 0.028 and 0.034 for 1716 and 2164 reflections with I ≥ 3σ(I), respectively.

scholarly journals The stereochemistry and conformation of lignin as judged by X-ray crystallographic investigations of lignin model compounds: Arylglycerol beta-guaiacyl ethers

BioResources ◽  
2007 ◽  
Vol 2 (4) ◽  
pp. 590-597
Author(s):  
Vratislav Langer ◽  
Knut Lundquist ◽  
Jim Parkås
Keyword(s):  
Nmr Spectra ◽  
Crystallographic Data ◽  
Structural Elements ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
X Ray ◽  
X Ray Crystallography ◽  
Conformational Variations ◽  
Structural Differences ◽  
Lignin Model

The conformations of a variety of crystalline lignin models representing different diastereomeric forms of structural elements in lignin of the arylglycerol b-guaiacyl ether type have been studied using X-ray crystallography. Based on X-ray crystallographic data, sequences of units attached to each other by b-guaiacyl ether linkages were constructed. The appearance of the resulting oligomers shows that stereoisomerism can be expected to influence the shape of the lignin molecules to a great extent. The constructed oligomers provide an idea about the contribution to the complexity of lignins by stereochemistry alone. It is proposed that structural differences, together with conformational variations, are the main reasons for the broadness of the signals in NMR spectra of lignins.

scholarly journals Effect of lignin structure on adsorbable organic halogens formation in chlorine dioxide bleaching

2019 ◽  
Vol 6 (2) ◽  
pp. 182024 ◽  
Author(s):  
Lisheng Shi ◽  
Jiayan Ge ◽  
Shuangxi Nie ◽  
Chengrong Qin ◽  
Shuangquan Yao
Keyword(s):  
Chlorine Dioxide ◽  
Model Compound ◽  
Pulp Bleaching ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Lignin Model Compound ◽  
Lignin Model ◽  
Organic Halogens ◽  
Adsorbable Organic Halogens ◽  
Lignin Structure

Adsorbable organic halogens (AOX) are formed in pulp bleaching as a result of the reaction of residual lignin with chlorine dioxide. The natural structure of lignin is very complex and it tends to be damaged by various extraction methods. All the factors can affect the study about the mechanism of AOX formation in the reaction of lignin with chlorine dioxide. Lignin model compounds, with certain structures, can be used to study the role of different lignin structures on AOX formation. The effect of lignin structure on AOX formation was determined by reacting phenolic and non-phenolic lignin model compound with a chlorine dioxide solution. Vanillyl alcohol (VA) and veratryl alcohol (VE) were selected for the phenolic and non-phenolic lignin model compound, respectively. The pattern consumption of lignin model compounds suggests that both VA and VE began reacting with chlorine dioxide within 10 min and then gradually steadied. The volume of AOX produced by VE was significantly higher than that produced by VA for a given initial lignin model compound concentration. In a solution containing a combination of VA and VE in chlorine dioxide, VE was the dominant producer of AOX. This result indicates that the non-phenolic lignin structure was more easily chlorinated, while the phenolic lignin structure was mainly oxidized. In addition, AOX content produced in the combined experiments exceeded the total content of the two separate experiments. It suggested that the combination of phenolic and non-phenolic lignin structure can promote AOX formation.

Synthesis of meso-phenyl-4,6-dipyrrins, preparation of their Cu(II), Ni(II), and Zn(II) chelates, and structural characterization of bis[meso-phenyl-4,6-dipyrrinato]Ni(II)

1996 ◽  
Vol 74 (11) ◽  
pp. 2182-2193 ◽  
Author(s):  
Christian Brückner ◽  
Veranja Karunaratne ◽  
Steven J. Rettig ◽  
David Dolphin
Keyword(s):  
Dihedral Angle ◽  
Direct Methods ◽  
Metal Chelates ◽  
Central Metal ◽  
Full Matrix ◽  
X Ray ◽  
X Ray Crystallography ◽  
Transition Metal Chelates ◽  
Square Planar

meso-Phenyldipyrromethanes can be oxidized by 2,6-dicyano-3,5-dichloro-para-benzoquinone (DDQ) to the corresponding meso-phenyldipyrrins. As expected, these novel, stable bipyrrolic pigments readily form metal chelates with copper(II), nickel(II), and zinc(II). Their UV–VIS spectra are compared with a series of known alkyl-substituted dipyrrin chelates and, based on the UV–VIS spectral analysis, the dihedral angle between the two ligands in the bis[meso-phenyldipyrrinato]Ni(II) complex was calculated to be 42°. The molecular structure of this complex was determined by X-ray crystallography, essentially confirming the calculation. Crystals of C30H22N4Ni are orthorhombic, a = 17.156(3), b = 35.217(1), c = 7.886(1) Å, Z = 8, space group Fddd. The structure was solved by direct methods and refined by full-matrix least-squares procedures to R = 0.040 and Rw = 0.031 for 1058 reflections with I ≥ 3σ(F2). The central nickel is coordinated in a distorted square-planar fashion by four nitrogens. The pair of the planar dipyrrinato ligands enclose a dihedral angle of 38.5°. This is the lowest angle reported for nickel(II) complexes of this kind. As a result of this, and in sharp contrast to previously described nickel(II) dipyrrin chelates, the central metal is diamagnetic. Key words: meso-phenyldipyrromethanes, meso-phenyldipyrrins, meso-phenyldipyrrinato transition metal chelates, X-ray crystallography.

Reaction of lignin model compounds with pulp bleaching chemicals

1995 ◽  
Vol 10 (2) ◽  
pp. 119-121 ◽  
Author(s):  
Esa Vilen ◽  
Douglas W. Reeve ◽  
A. Bruce McKague ◽  
Steven J. Rettig ◽  
James Trotter
Keyword(s):  
Pulp Bleaching ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Lignin Model

X-Ray structure determination of 1,2-anhydro-3,4:5,6-di-O-isopropylidene-1-C-nitro-D-mannitol

1988 ◽  
Vol 66 (7) ◽  
pp. 1600-1604 ◽  
Author(s):  
Walter A. Szarek ◽  
George W. Hay ◽  
Ramesh K. Sood ◽  
Konia Trouton ◽  
Suzanne Fortier
Keyword(s):  
Crystal Structure ◽  
Hydrogen Peroxide ◽  
Direct Methods ◽  
Major Product ◽  
Calculated Density ◽  
Aqueous Sodium ◽  
X Ray ◽  
X Ray Crystallography ◽  
Cell Dimensions

The structure of the major product of the reaction of 1,2-dideoxy-3,4:5,6-di-O-isopropylidene-1-C-nitro-D-arabino-hex-1-enitol with 30% hydrogen peroxide and aqueous sodium hydrogencarbonate has been confirmed by X-ray crystallography to be that of 1,2-anhydro-3,4:5,6-di-O-isopropylidene-1-C-nitro-D-mannitol (2). The crystal structure of 2, C12H19NO7, is orthorhombic, P212121, with cell dimensions a = 10.269(3), b = 15.115(7), c = 9.295(8) Å, and Z = 4. The calculated density is Dx = 1.336 gcm−3. The structure was solved by direct methods and refined to a residual R = 0.052. The molecule has a 2G− conformation having bond lengths and angles in agreement with those observed in related structures, except for the C(1)—C(2), C(2)—C(3), and O(2N)—N bond distances which were found to be unusually small.

Oxalate formation during ClO2 bleaching of bamboo kraft pulp

2020 ◽  
Vol 35 (1) ◽  
pp. 18-24
Author(s):  
Hailong Li ◽  
Chao Du ◽  
Shujuan Ge ◽  
Mengru Liu
Keyword(s):  
Chlorine Dioxide ◽  
Kraft Pulp ◽  
Reaction System ◽  
Kappa Number ◽  
Pulp Bleaching ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Bleaching Process ◽  
Prolonged Reaction Time ◽  
Lignin Model

AbstractThis study aimed to investigate the oxalate formation mechanism during chlorine dioxide ({\mathrm{ClO}_{2}}) bleaching of bamboo kraft pulp, and thus explore favourable {\mathrm{ClO}_{2}} bleaching conditions to better control oxalate formation. The amount of oxalate formed varied linearly with {\mathrm{ClO}_{2}} dosage within the whole research range, while it rose exponentially within the first 90 mins of pulp bleaching. Then the actual bleaching process was simulated by reacting {\mathrm{ClO}_{2}} with three representative lignin model compounds and comparatively studied. The rule of oxalate formation in the simulated reaction system was identical to that in pulp bleaching by {\mathrm{ClO}_{2}}, except for oxalate production by veratraldehyde with prolonged reaction time. Under identical conditions, vanillin formed the highest amount of oxalate, while veratraldehyde formed the least. Furthermore, the amount of oxalate formed increased by 19.59 mg/kg when the kappa number of the delignified pulp was reduced by one unit. Considering the satisfactory pulp brightness and decreased oxalate formation, the recommended conditions for {\mathrm{ClO}_{2}} bleaching of bamboo kraft pulp were a {\mathrm{ClO}_{2}} dosage of 4 %, 60 °C and 70 mins.

scholarly journals Crystal Structure of Poly[(acetone-O)-3-((3,4-dimethoxyphenyl)(4-hydroxy-2-oxo-2H-chromen-3-yl)methyl)-(2-oxo-2H-chromen-4-olate)sodium]

2010 ◽  
Vol 2010 ◽  
pp. 1-7
Author(s):  
Anita Penkova ◽  
Pascal Retailleau ◽  
Ilia Manolov
Keyword(s):  
Crystal Structure ◽  
Least Squares ◽  
Direct Methods ◽  
Orthorhombic System ◽  
Full Matrix ◽  
X Ray ◽  
X Ray Crystallography

The structure of Poly[(acetone-O)-3-((3,4-dimethoxyphenyl)(4-hydroxy-2-oxo-2H-chromen-3-yl)methyl)-(2-oxo-2H-chromen-4-olate)sodium] was determined by X-ray crystallography. The compound crystallizes in an orthorhombic system and was characterized thus P 21 21 21, a=9.967(2) Å, b=11.473(3) Å, c=22.176(5) Å. Z=4, V=2535.9(10) Å3. The crystal structure was solved by direct methods and refined by full-matrix least-squares on F2 to final values of R1=0.0601 and wR2=0.1515.

The cycloaddition of norbornadiene to (triphenylphosphoranediyl)aminocyclotrithiatriazene; the crystal and molecular structure of Ph3PN—S3N3•C7H8

1983 ◽  
Vol 61 (9) ◽  
pp. 2062-2067 ◽  
Author(s):  
Stephen W. Liblong ◽  
Richard T. Oakley ◽  
A. Wallace Cordes ◽  
Mark C. Noble
Keyword(s):  
Molecular Structure ◽  
Crystal And Molecular Structure ◽  
Direct Methods ◽  
Chair Conformation ◽  
Monoclinic Space Group ◽  
Frontier Orbitals ◽  
Full Matrix ◽  
X Ray ◽  
X Ray Crystallography ◽  
Kinetics Of

The reaction of norbornadiene with (triphenylphosphoranediyl)aminocyclotrithiatriazene produces the cycloadduct Ph3PN—S3N3•C7H8. The crystal and molecular structure of this compound has been determined by X-ray crystallography. Crystals of Ph3PN—S3N3•C7H8 are monoclinic, space group P21/c, a = 9.757(1), b = 15.114(1), c = 16.535(2) Å, β = 100.73(1)°, V = 2395.7(9) Å3, and Z = 4. The structure was solved by direct methods and refined by Fourier and full-matrix least-squares procedures to give a final R of 0.040 and Rw of 0.058 for 2620 observed reflections. The structure reveals that the S3N3 ring adds to norbornadiene in an exo fashion via two sulphur atoms. The S3N3 ring adopts a chair conformation with the three ligands occupying axial positions on the same side of the ring. The relative rates of this and other cycloadditions involving SN substrates and olefins are discussed in terms of the energies of the interacting frontier orbitals. The results suggest that HOMO(olefin)–LUMO(SN substrate) interactions control the kinetics of these reactions.

Lignin to Value-Added Chemical Synthesis

2020 ◽  
Vol 16 ◽  
Author(s):  
Mahdieh Sharifi ◽  
Ramyakrishna Pothu ◽  
Rajender Boddula ◽  
Inamuddin
Keyword(s):  
Ionic Liquids ◽  
Lignocellulosic Biomass ◽  
Academic Research ◽  
Power Saving ◽  
Value Added ◽  
Glycerol Ether ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Biomass Activity ◽  
Lignin Model

Background: There is a developing demand for innovation in petroleum systems replacements. Towards this aim, lignocellulosic biomass suggested as a possible sustainable source for the manufacturing of fuels and produced chemicals. The aims of this paper are to investigate different kinds of β-O-4 lignin model compounds for the production of value-added chemicals in presence of ionic liquids. Especially, a cheap β-O-4 lignin model Guaiacol glycerol ether (GGE) (Guaifenesin) is introduced to produce valuable chemicals and novel products. Methods: Research related to chemical depolymerization of lignocellulosic biomass activity is reviewed, the notes from different methods such as thermal and microwave collected during at least 10 years. So, this collection provides a good source for academic research and it gives an efficient strategy for the manufacturing of novel value-added chemicals at an industrial scale. Results: This research presented that ionic liquid microwave-assisted is a power saving, cost efficient, fast reaction, and clean way with high selectively and purity for production of high value chemicals rather that conversional heating. Guaiacol and catechol are some of these valuable chemicals that is produced from β-O-4 lignin model compounds with high word demands that are capable to produce in industry scale. Conclusion: The β-O-4 lignin model compounds such as Guaiacol glycerol ether (GGE) (Guaifenesin) are good platform for developing food materials, perfumery, biorefinery, and pharmaceutical industry by ionic liquids-assisted lignin depolymerization method.

Sign in / Sign up

Export Citation Format

Share Document