Kinetic effects induced by cellulose on water-catalyzed reactions. Hydrolysis of 2,4-dinitrophenyl cellulose xanthate and some sugar xanthate ester analogues

1998 ◽  
Vol 76 (6) ◽  
pp. 960-965 ◽  
Author(s):  
Eduardo Humeres ◽  
Luiz Fernando Sequinel ◽  
Mauricéa Nunes ◽  
Célia MS Oliveira ◽  
Patrick J Barrie
Keyword(s):  
Cellulose Xanthate ◽  
First Order Kinetics ◽  
Acetone Water ◽  
Spontaneous Hydrolysis ◽  
Hydrolysis Of Cellulose ◽  
Entropy Of Activation ◽  
Kinetic Effects ◽  
Catalyzed Reactions ◽  
Parallel Reactions ◽  
Hydrolysis Of

The hydrolysis of 2,4-dinitrophenyl cellulose xanthate (CelXDNP) was studied in 10% v/v aqueous ethanol at 25°C and μ = 0.1 (KCl). The water-catalyzed hydrolysis showed that, as for p-nitrobenzyl cellulose xanthate, it occurs through two parallel reactions with rate constants k'H2O = 4.40 x 10-3 s-1 for the fast hydrolysis, and k''H2O = 6.90 x 10-5 s-1 for the slow hydrolysis. The entropy of activation of the fast hydrolysis was 0.7 ± 1.8 cal K-1 mol-1. External nucleophiles such as hydroxide and simple amines show simple first-order kinetics. The spontaneous hydrolysis of CelXDNP in acetone-water mixtures indicates that the fast reaction does not occur through water polymers and that for water molarity higher than 30 M there are no acetone molecules (or very few) in the highly ordered cybotactic region of cellulose. The spontaneous hydrolysis of methyl 4,6-O-benzylidene- α -D-glucopyranoside 3-(S-p-nitrobenzyl-xanthate) although is faster than the 6-isomer, it is slower than the fast hydrolysis of p-nitrobenzyl cellulose xanthate (CelXNB). Also Δ Sdouble dagger is highly negative (-41.0 cal K-1 mol-1), as it is for alkyl and sugar analogues. Only for the fast hydrolyses of CelXDNP and CelXNB is the entropy of activation almost zero. It is concluded that there is no neighbouring OH effect on the fast hydrolysis of cellulose xanthate esters. Key words: hydrolysis, water catalysis, cellulose xanthate esters, methyl glucose, xanthate esters, neighbouring OH effect.

scholarly journals A Fast, Inexpensive, and Safe Method for Residue Analysis of Meptyldinocap in Different Fruits by Liquid Chromatography/Tandem Mass Spectrometry

2010 ◽  
Vol 93 (6) ◽  
pp. 1957-1964 ◽  
Author(s):  
Kaushik Banerjee ◽  
Soma Dasgupta ◽  
Manjusha R Jadhav ◽  
Dattatraya G Naik ◽  
Axel Patrick Ligon ◽  
...  
Keyword(s):  
Ethyl Acetate ◽  
Residue Analysis ◽  
First Order ◽  
First Order Kinetics ◽  
Free Energy Of Activation ◽  
Subsequent Hydrolysis ◽  
Liquid Chromatography Tandem Mass ◽  
Rate Kinetics ◽  
Entropy Of Activation ◽  
Hydrolysis Of

Abstract An analytical method is reported for residue analysis of the fungicide meptyldinocap in different fruit matrixes that involves extraction with ethyl acetate, hydrolysis of the residues with ethanolamine, and determination by LC/MS/MS. The method involves extraction of 10 g sample with 10 mL ethyl acetate; evaporation of the ethyl acetate phase to dryness, and subsequent hydrolysis of the residues to 4,6-dinitro-2-(1-methylheptyl) phenol on reaction with 1 ethanolamine. The pH of this hydrolyzed product was neutralized with formic acid and analyzed by LC/MS/MS. The hydrolysis reaction followed pseudo-first-order kinetics, and the reaction product was spectroscopically confirmed as 2-(1-methylheptyl)-4,6-dinitrophenol. The method offered >80 recoveries at an LOQ of 10 ng/g for grape and mango, 25 ng/g for pomegranate with intralaboratory Horwitz ratio <0.5, and measurement uncertainties <10 at LOQ levels. Considering first-order rate kinetics, activation energy, enthalpy of activation, and entropy of activation varied as solvent > mango > grape > pomegranate. Free energy of activation at 298 K was higher than at 280 K and was similar for solvent and three matrixes at both temperatures.

Effect of Pressure on the Alkaline Hydrolysis of Ethyl Acetate in Acetone–Water Solutions. Parameters of Activation at Constant Volume

1975 ◽  
Vol 53 (22) ◽  
pp. 3414-3418 ◽  
Author(s):  
M. L. Tonnet ◽  
E. Whalley
Keyword(s):  
Ethyl Acetate ◽  
Solvent Effect ◽  
Internal Energy ◽  
Alkaline Hydrolysis ◽  
Constant Pressure ◽  
Constant Volume ◽  
Acetone Water ◽  
Entropy Of Activation ◽  
Enthalpy And Entropy ◽  
Hydrolysis Of

The effect of pressures up to 3 kbar on the rate of the base-catalyzed hydrolysis of ethyl acetate in acetone–water mixtures has been measured. From these measurements and the enthalpy and entropy of activation at constant pressure measured by others, the internal energy and entropy of activation at constant volume have been obtained as a function of solvent composition. The constant-volume parameters of activation vary with composition in a simpler way than the constant-pressure parameters. It seems likely that theoretical discussions of the solvent effect are easier if they are based on the constant-volume parameters. At low acetone concentrations, the addition of acetone reduces the rate constant at low pressure, but increases it at 3 kbar.

Hydrolysis and aminolysis of alkyl xanthate esters and cellulose analogues

1999 ◽  
Vol 77 (5-6) ◽  
pp. 1050-1056 ◽  
Author(s):  
Eduardo Humeres ◽  
Valdir Soldi ◽  
Marilene Klug ◽  
Mauricéa Nunes ◽  
Célia MS Oliveira ◽  
...  
Keyword(s):  
Cellulose Xanthate ◽  
Covalent Bond ◽  
Hydroxide Ion ◽  
First Order ◽  
Tetrahedral Intermediate ◽  
Rate Determining Step ◽  
First Order Kinetics ◽  
Elimination Mechanism ◽  
Catalyzed Reactions ◽  
C Nmr

The hydrolysis and aminolysis of a series of S-substituted O-alkylxanthate esters was studied in 20% v/v aqueous methanol at 35°C. The pH-rate profiles of the hydrolyses showed water and hydroxide-ion-catalyzed reactions. The reaction of 2,4-dinitrophenyl cellulose xanthate (CelXDNP) and p-nitrobenzyl cellulose xanthate (CelXNB) with polyalanine and lysozyme produced a covalent bond between the polypeptide and the cellulose matrix, as shown by solid-state 13C NMR. However, the nature of the bonding could not be identified. The reaction of nucleophiles (H2O, OH-, RNH2) and xanthic esters was consistent with an addition-elimination mechanism through a tetrahedral intermediate. Brønsted plots against the pKa of the nucleophile (βnu) or the nucleofuge of the substrate (βlg) were used to characterize the rate-determining step. The pKa values of the nucleophiles ranged between -1.74 and 15.74, and for the nucleofuges, they were in the range of 10.50-0.92. For nucleophiles with pKa values up to about 10, βlg was 0.10-0.15, and βnu changed from 0.48 to 0.35 for the strongest electron-withdrawing nucleofuge. It was concluded that the water-catalyzed hydrolyses, and also aminolyses with moderately basic amines, occur with rate-determining formation of the tetrahedral intermediate. For strong bases such as hydroxide ion, the disappearance of the intermediate becomes the slowest step. The reaction of cellulose xanthic esters with external nucleophiles as hydroxide ion and amines shows simple first-order kinetics and is slower than alkyl or sugar xanthates, probably due to the diffusion effect through the tight cybotactic region of cellulose. Key words: hydrolysis, aminolysis, alkyl xanthic esters, cellulose xanthic esters, sugar xanthic esters.

PRESSURE EFFECT AND MECHANISM IN ACID CATALYSIS: V. THE HYDROLYSIS OF ACETIC ANHYDRIDE

1959 ◽  
Vol 37 (8) ◽  
pp. 1360-1366 ◽  
Author(s):  
J. Koskikallio ◽  
D. Pouli ◽  
E. Whalley
Keyword(s):  
Acetic Anhydride ◽  
Acid Catalysis ◽  
Pressure Effect ◽  
Valid Method ◽  
Acetone Water ◽  
Entropy Of Activation ◽  
Acid Catalyzed ◽  
Hydrolysis Of

The spontaneous and the acid-catalyzed hydrolyses of acetic anhydride have been measured as a function of temperature over the range 0 to 40 °C, as a function of pressure over the range 0 to 3 kb at 0 °C, and as a function of solvent over the range 0 to 70.3% w/w acetone–water at 0 °C. The results are discussed with reference to the mechanisms of the hydrolyses. The volume and entropy of activation of the acid-catalyzed hydrolysis are −17.1 ± ~1.3 cm3 mole−1 and ~ −20 cal deg−1 mole−1, showing that the mechanism[Formula: see text]suggested because the rate was proportional to Hammett's h0, is not correct. It follows that the Zucker–Hammett hypothesis is invalid for this reaction, as we have shown previously for other reactions, and hence that it does not provide a valid method of distinguishing between the A-1 and A-2 mechanisms.

THE PRESENCE OF MONOTHIOCARBONATE SUBSTITUENTS IN CELLULOSE XANTHATES

1960 ◽  
Vol 38 (8) ◽  
pp. 1381-1394 ◽  
Author(s):  
D. A. Andrews ◽  
F. G. Hurtubise ◽  
H. Krässig
Keyword(s):  
Acid Hydrolysis ◽  
Infrared Spectra ◽  
Cellulose Xanthate ◽  
Ultraviolet Spectroscopy ◽  
Hydrolysis Of Cellulose ◽  
Comparison Of The Results ◽  
Hydrolysis Of

The presence of monothiocarbonate substituents in viscose has been demonstrated by the infrared spectra of the gases evolved during the acid hydrolysis of cellulose xanthate salts and viscose. A comparison of the results of various methods of sulphur determination and the results obtained by ultraviolet spectroscopy has been made. The results of investigations on sodium cellulose monothiocarbonate preparations support the concept of monothiocarbonate substitution.

Immobilized Nanoparticles-Mediated Enzymatic Hydrolysis of Cellulose for Clean Sugar Production: A Novel Approach

2019 ◽  
Vol 15 (3) ◽  
pp. 296-303 ◽  
Author(s):  
Swapnil Gaikwad ◽  
Avinash P. Ingle ◽  
Silvio Silverio da Silva ◽  
Mahendra Rai
Keyword(s):  
Catalytic Activity ◽  
Enzymatic Hydrolysis ◽  
Immobilized Enzyme ◽  
Free Enzyme ◽  
Magnetic Nanomaterials ◽  
Sugar Production ◽  
Cellulase Enzyme ◽  
Enzymatic Hydrolysis Of Cellulose ◽  
Hydrolysis Of Cellulose ◽  
Hydrolysis Of

Background: Enzymatic hydrolysis of cellulose is an expensive approach due to the high cost of an enzyme involved in the process. The goal of the current study was to apply magnetic nanomaterials as a support for immobilization of enzyme, which helps in the repeated use of immobilized enzyme for hydrolysis to make the process cost-effective. In addition, it will also provide stability to enzyme and increase its catalytic activity. Objective: The main aim of the present study is to immobilize cellulase enzyme on Magnetic Nanoparticles (MNPs) in order to enable the enzyme to be re-used for clean sugar production from cellulose. Methods: MNPs were synthesized using chemical precipitation methods and characterized by different techniques. Further, cellulase enzyme was immobilized on MNPs and efficacy of free and immobilized cellulase for hydrolysis of cellulose was evaluated. Results: Enzymatic hydrolysis of cellulose by immobilized enzyme showed enhanced catalytic activity after 48 hours compared to free enzyme. In first cycle of hydrolysis, immobilized enzyme hydrolyzed the cellulose and produced 19.5 ± 0.15 gm/L of glucose after 48 hours. On the contrary, free enzyme produced only 13.7 ± 0.25 gm/L of glucose in 48 hours. Immobilized enzyme maintained its stability and produced 6.15 ± 0.15 and 3.03 ± 0.25 gm/L of glucose in second and third cycle, respectively after 48 hours. Conclusion: This study will be very useful for sugar production because of enzyme binding efficiency and admirable reusability of immobilized enzyme, which leads to the significant increase in production of sugar from cellulosic materials.

In Situ Microscopy for In-line Monitoring of the Enzymatic Hydrolysis of Cellulose

2013 ◽  
Vol 85 (17) ◽  
pp. 8121-8126 ◽  
Author(s):  
Britta Opitz ◽  
Andreas Prediger ◽  
Christian Lüder ◽  
Marrit Eckstein ◽  
Lutz Hilterhaus ◽  
...  
Keyword(s):  
Enzymatic Hydrolysis ◽  
Enzymatic Hydrolysis Of Cellulose ◽  
Hydrolysis Of Cellulose ◽  
Hydrolysis Of

Enhanced Hydrolysis of Cellulose to Reducing Sugars on Kaolinte Clay Activated by Mineral Acid

2021 ◽  
Author(s):  
Yuxiao Dong ◽  
Dongshen Tong ◽  
Laibin Ren ◽  
Xingtao Chen ◽  
Hao Zhang ◽  
...  
Keyword(s):  
Reducing Sugars ◽  
Mineral Acid ◽  
Hydrolysis Of Cellulose ◽  
Hydrolysis Of

Role and significance of beta-glucosidases in the hydrolysis of cellulose for bioethanol production

2013 ◽  
Vol 127 ◽  
pp. 500-507 ◽  
Author(s):  
Reeta Rani Singhania ◽  
Anil Kumar Patel ◽  
Rajeev K. Sukumaran ◽  
Christian Larroche ◽  
Ashok Pandey
Keyword(s):  
Bioethanol Production ◽  
Hydrolysis Of Cellulose ◽  
Hydrolysis Of
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