SOME FACTORS AFFECTING THE KÖNIGS–KNORR SYNTHESIS OF GLYCOSIDES

1961 ◽  
Vol 39 (10) ◽  
pp. 2025-2034 ◽  
Author(s):  
H. R. Goldschmid ◽  
A. S. Perlin
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Silver Oxide ◽  
Condensation Reaction ◽  
Side Reaction ◽  
Ortho Ester ◽  
Factors Affecting ◽  
High Molecular Weight Compound ◽  
Elemental Iodine

Glycosyl halides decompose readily in the presence of silver oxide under conditions generally used for the Königs–Knorr synthesis of glycosides. This "side reaction" probably accounts for the low yields commonly obtained in the synthesis of oligosaccharides, particularly those involving the formation of a glycosidic union through an unreactive secondary position. The rate of the side reaction, as well as that of the normal condensation reaction, is dependent on the condition of the silver oxide, and is retarded markedly by elemental iodine. This latter effect appears to be related to the improved yield obtained in Königs–Knorr syntheses when iodine is used. Among the products formed in the decomposition of 2,3,4,6-tetra-O-acetyl-α-D-mannopyranosyl bromide are 2,3,4,6-tetra-O-acetyl-D-mannose, a heptaacetyl 1,2,1′-linked dimeric orthoacetate, and a second high-molecular-weight compound that also shows ortho ester properties.

scholarly journals High molecular weight SOA formation during limonene ozonolysis: insights from ultrahigh-resolution FT-ICR mass spectrometry characterization

2012 ◽  
Vol 12 (1) ◽  
pp. 2167-2197
Author(s):  
S. Kundu ◽  
R. Fisseha ◽  
A. L. Putman ◽  
T. A. Rahn ◽  
L. R. Mazzoleni
Keyword(s):  
Mass Spectrometry ◽  
Molecular Weight ◽  
High Molecular Weight ◽  
Homologous Series ◽  
Condensation Reaction ◽  
Reaction Pathways ◽  
Ultrahigh Resolution ◽  
Group Iii ◽  
Group Ii ◽  
Ft Icr

Abstract. The detailed molecular composition of secondary organic aerosols (SOA) from limonene ozonolysis was studied using ultrahigh-resolution Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. High molecular weight (MW) compounds (m/z > 300) were found to constitute a significant number fraction of the identified SOA components. Double bond equivalents (DBE = the number of rings plus the number of double bonds) increased with MW. The O:C ratios and relative abundances of compounds decreased with increasing MW. The mass spectra of limonene contain 4 distinct clusters of negative ions: Group I (140 < m/z < 300), Group II (300 < m/z < 500), Group III (500 < m/z < 700) and Group IV (700 < m/z < 850). A number of CH2 and O homologous series of low MW SOA (Group 1) with carbon number 7–15 and oxygen number 3–9 were observed. Their occurrence can be explained with isomerization and elimination reactions of Criegee radicals, reactions between alkyl peroxy radicals, and scission of alkoxy radicals resulting from the Criegee radicals. Additionally, fragmentation analysis and observations of formaldehyde homologous series provide evidence for aerosol growth by the reactive uptake of generated gas-phase carbonyls in limonene ozonolysis. The decreasing O:C ratios between group of compounds indicated the importance of condensation (aldol and esterification) reaction pathways for high MW compound formation. However, the prominent DBE changes of 2 between the groups of compounds and selected fragmentation (MS/MS) analysis of Group II and Group III ions indicated a predominance of non-condensation (hydroperoxide, Criegee and hemi-acetal) reaction pathways. A reaction matrix created with the combination of low MW SOA, hydroperoxides, and Criegee radicals indicated higher frequencies for the hemi-acetal and condensation reaction pathways. Overall, the combined approach confirms the importance of non-condensation reaction pathways over condensation reaction pathways. Among the non-condensation reaction pathways, hemi-acetal reactions appear to be most dominant followed by hydroperoxide and Criegee reactions.

scholarly journals Cutinase-Like Enzyme from the Yeast Cryptococcus sp. Strain S-2 Hydrolyzes Polylactic Acid and Other Biodegradable Plastics

2005 ◽  
Vol 71 (11) ◽  
pp. 7548-7550 ◽  
Author(s):  
Kazuo Masaki ◽  
Numbi Ramudu Kamini ◽  
Hiroko Ikeda ◽  
Haruyuki Iefuji
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Polylactic Acid ◽  
Biodegradable Plastics ◽  
Remote Homology ◽  
High Molecular Weight Compound ◽  
Polybutylene Succinate

ABSTRACT A purified lipase from the yeast Cryptococcus sp. strain S-2 exhibited remote homology to proteins belonging to the cutinase family rather than to lipases. This enzyme could effectively degrade the high-molecular-weight compound polylactic acid, as well as other biodegradable plastics, including polybutylene succinate, poly (ε-caprolactone), and poly(3-hydroxybutyrate).

Lignin-Carbohydrate Condensation Product Formation in a Biomimetic Model Pulp Bleaching System

Holzforschung ◽  
2003 ◽  
Vol 57 (4) ◽  
pp. 385-390 ◽  
Author(s):  
C. C. Walker ◽  
T. J. McDonough ◽  
R. J. Dinus ◽  
K.-E. L. Eriksson
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Condensation Product ◽  
Condensation Reaction ◽  
Product Formation ◽  
Water Soluble ◽  
Hydroxyethyl Cellulose ◽  
Pulp Bleaching ◽  
High Molecular Weight Product ◽  
Molecular Weight Product

Abstract Three biomimetic compounds were evaluated for their ability to preferentially degrade lignin in the presence of carbohydrate using two water-soluble polymeric model compounds: lignosulfonate and hydroxyethyl cellulose (HEC). The three biomimetic systems studied were FeSO4, Fe-EDTA and hemoglobin, each in the presence of hydrogen peroxide. When both polymeric substrates were present, a high molecular weight product was observed to form upon addition of H2O2. This high molecular weight product is believed to be the result of a condensation reaction between lignosulfonate and HEC. The condensation product was also observed to form in the absence of biomimetic catalyst. For all reactions, the molecular weight of the condensation product was observed to decrease with increasing reaction time. By altering the ratio of lignosulfonate to HEC, a limit was observed in the relative amount of condensation product formed. The formation of this condensation product is believed to limit the effectiveness of acidic bleaching systems.

Preparation and characterization of poly(arylene ether isoxazole)s by fluoride ion-mediated aromatic nucleophilic displacement reactions

1994 ◽  
Vol 6 (4) ◽  
pp. 303-319 ◽  
Author(s):  
C G Herbert ◽  
R G Bass
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
High Performance ◽  
Weight Control ◽  
Side Reaction ◽  
Polymer Chains ◽  
Fluoride Ion ◽  
Silyl Ether ◽  
Good Thermal Stability ◽  
Arylene Ether

As part of a continuing effort to prepare novel thermally stable high-performance polymers, poly(arylene ether isoxazole)s have been prepared by fluoride ion-catalysed aromatic nucleophilic substitution reactions with bis(trimethylsiloxyphenyl) isoxazoles and activated bisarylhalides in diphenyl sulphone. Initial investigations involving the preparation of these materials with isoxazole bisphenols and activated bisarylhalides in the presence of potassium carbonate indicated that, under reaction conditions necessary to prepare high-molecular-weight materials, the isoxazole monomer was converted to an enamino ketone. This side reaction was avoided by using fluoride as a base. However, trimethylsilyt ether derivatives of the isoxazole bisphenols were required in these polymerizations for the preparation of high-molecular-weight materials. Moderate to high inherent viscosity (htAh: 0.43-0.87 dl g -) materials with good thermal stability (air: 409-477C, helium: 435-512C) can be prepared by the silyl ether method. Glass transition temperatures ranged from 182 to 225 C for polymers with phenyl pendants and from 170 to 214 C for those without. Molecular weight control by 2% endcapping and the incorporation of a phenyl pendant at the 4 position of the isoxazole is necessary to yield polymers soluble in polar aprotic solvents at room temperature. There is evidence, however, indicating the existence of crosslinks between the polymer chains when the silyl ether approach is utilized.

Synthesis and Properties of Substituted Germylhydrazines

1972 ◽  
Vol 50 (4) ◽  
pp. 553-561 ◽  
Author(s):  
L. K. Peterson ◽  
K. I. Thé
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Degree Of Substitution ◽  
Spectral Measurements ◽  
Mass Spectral ◽  
High Molecular Weight Compound ◽  
Condensed Product ◽  
New Compounds

By using reactions between Me3GeBr or Me2GeCl2 and appropriate lithium hydrazide salts, the following new compounds were prepared: Me2NN(R)GeMe3 (R = H, 1; Me, 2; GeMe3, 3; SiMe3, 4), Me3GeN(Me)NHGeMe3, 5a, MeNHN(GeMe3)2, 5b, (Me3Ge)2NN(Me)GeMe3, 6, Me3GeNHNHGeMe3, 7a, (Me3Ge)2NNH2, 7b, (Me)11Ge4N6H, 11, (Me2GeNNMe2)3, 12, Me2Ge[N(R′)NMe2]2 (R′ = Me, 13; SiMe3, 14). Thus the reaction of Me3GeBr with Li(MeN2H2) and with LiN2H3 gave mixtures of disubstituted isomers, 5a and b, and 7a and b, respectively, rather than mono-substituted derivatives. Reactions of Me2GeCl2 gave (i) an unresolvable, highly condensed product with LiN2H3; (ii) the high molecular weight compound 11, with Li(MeN2H2); and (iii) the cyclic trigermazane 12 with Me2NNHLi; the extent of self-condensation is a function of the degree of substitution of the hydrazine moiety. Reactions with protic reagents (H2O, MeOH, anhydrous HCl) effect cleavage of the Ge—N bond in germylhydrazines. New compounds were characterized on the basis of i.r., n.m.r., and mass spectral measurements.

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