Hydrolysis kinetics and mechanism of N'-(3-N-methylcarbamoyloxyphenyl)-N,N-dimethylformamidine

1980 ◽  
Vol 45 (4) ◽  
pp. 1065-1071 ◽  
Author(s):  
Alexandr Čegan ◽  
Jaroslav Šlosar ◽  
Miroslav Večeřa
Keyword(s):  
Reaction Mechanism ◽  
Paper Chromatography ◽  
Kinetics And Mechanism ◽  
Hydrolysis Rate ◽  
Hydrolysis Kinetics ◽  
Hydrolysis Products ◽  
Hydrolysis Rates ◽  
Ph Range ◽  
Hydrolysis Of

Hydrolysis of N' -(3-N-methylcarbamoyloxyphenyl)-N,N-dimethylformamidine (I) has been studied in mixture water-dioxane (4 : 1) at pH 1 to 13. The hydrolysis rates of methylcarbamoyl and dimethylformamidine groups are comparable within pH range 4 to 10, and they differ by as much as several orders of magnitude in pH ranges 1-3 and 11-13. The hydrolysis products of the whole pH range have been determined by paper chromatography, and reaction mechanism has been suggested on the basis of the measured hydrolysis rate constants.Effects of protonation and hydratation of dimethylformamidine group on the hydrolysis rate of the methylcarbamoyl group is discussed.

Hydrolysis of aluminum(III) ion in sodium nitrate medium

1991 ◽  
Vol 69 (1) ◽  
pp. 28-32 ◽  
Author(s):  
Nikola B. Milić ◽  
Živadin D. Bugarčić ◽  
Predrag T. Djurdjević
Keyword(s):  
Least Squares ◽  
Key Words ◽  
Sodium Nitrate ◽  
Emf Method ◽  
Nitrate Medium ◽  
Aluminium Concentration ◽  
Hydrolysis Products ◽  
The Stability ◽  
Ph Range ◽  
Hydrolysis Of

Hydrolysis of aluminum(III) ion in 3.0 M (Na)NO3 medium was studied by emf method at 25° C. Data cover the range 1–78 mM Al(III) within the pH range of 2.0–4.5. At a definite pH, the extent of hydrolysis increases with increasing aluminium concentration, thereby indicating the presence of polynuclear hydrolysis products. The least squares treatment of the data indicates the formation of polynuclear hydrolytic complexes [Formula: see text] [Formula: see text] and [Formula: see text] With the reactions written in the form[Formula: see text]the stability constants obtained were log (β2,2 = −7.55 ± 0.21, log β2,4 = −16.41 ± 0.13, and log (β3,4 = −13.24 ± 0.08. Distribution curves indicate that the complex [Formula: see text] is predominant. Key words: hydrolysis, aluminum(III) ion, hydrolytic complexes, aluminum(III) ion hydrolysis.

Effect of the α- and γ-Hydroxyls on the Alkaline Hydrolysis Rate of Nonphenolic β-0-4 Lignin Diastereomers

Holzforschung ◽  
2002 ◽  
Vol 56 (1) ◽  
pp. 67-72 ◽  
Author(s):  
Dexter L. Criss ◽  
Thomas Elder ◽  
Thomas H. Fisher ◽  
Tor P. Schultz
Keyword(s):  
Computational Modeling ◽  
Alkaline Hydrolysis ◽  
Rate Ratio ◽  
Electronic Effect ◽  
Activation Parameters ◽  
Hydrolysis Rate ◽  
Significant Extent ◽  
Hydrolysis Rates ◽  
Lignin Model ◽  
Hydrolysis Of

Summary Nonphenolic β-0-4 erythro and threo lignin model diastereomers with various γ-groups (CH3, CH2-O-CH3, and CH2OH) and Cα-substituents (OH, OCH3) were synthesized, and the alkaline hydrolysis rates and activation parameters determined. In addition, two of the diastereomer pairs were computationally modeled and the thermodynamic values for the ionization of the α- or γ-hydroxyl, and subsequent displacement of the phenolate group to form an epoxide intermediate, were determined. The results suggest that the erythro γ-hydroxyl may participate in the hydrolysis to a significant extent, which results in a relatively high erythro/threo rate ratio for the α,γ-di-OH isomers. The influence of the erythro γ-hydroxyl on the hydrolysis rate may be due to the relatively favorable stability of the erythro γ-oxyanion. The electronic effect of the g-substituent appears to influence how fast the α-hydroxyl displaces the phenoxyl. We had previously suggested that the γ-substituent sterically inhibits hydrolysis of the threo isomer, and computational modeling confirmed this.

scholarly journals Genetic control of the hydrolysis of aromatic esters by sheep plasma A-esterase

1966 ◽  
Vol 7 (3) ◽  
pp. 373-382 ◽  
Author(s):  
R. M. Lee
Keyword(s):  
Esterase Activity ◽  
Phosphate Esters ◽  
Hydrolysis Rate ◽  
Aromatic Esters ◽  
Hydrolysis Rates ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of ◽  
Naphthyl Acetate ◽  
Genetic Marking ◽  
Genetic Hypothesis

1. The rate of hydrolysis by sheep plasma of some carboxylic and phosphate esters has been determined for a random flock, and for a flock previously selected for its ability to hydrolyse di-(2-chloroethyl) aryl phosphates.2. A discontinuous variation in hydrolysis rate was found with all substrates tested and, using combinations of substrates, six types of plasma could be distinguished, each type having a different pattern of esterase activity.3. The most useful substrates for distinguishing between phenotypes were 1-naphthyl acetate and 4-ethoxycarbonylcoumarin-7-yl acetate. Three rates of hydrolysis were possible for each of these esters, and the highest rate for one was invariably combined with the lowest rate for the other, although the converse did not apply.4. To explain these results, and those of Lee (1964), it has been postulated that the quantitative production of esterase hydrolysing 1-naphthyl acetate is governed by the presence of an allele, termed Esa, at a particular gene locus. Similarly, the production of esterase hydrolysing 4-ethoxycarbonylcoumarin-7-yl acetate is determined by allele Esb, and where neither substrate is attacked the presence of a third allele, Esc, is proposed.5. The hydrolysis rates of haloxon, 1-naphthyl butyrate and 4-nitrophenyl butyrate varied in the same way as that of 1-naphthyl acetate, whereas the hydrolysis of indophenyl acetate followed the same pattern as that of 4-ethoxycarbonylcoumarin-7-yl acetate. The variation in hydrolysis rate of Coroxon could be explained by assuming that Esa and Esb are equal in this respect.6. A mating experiment produced results which were in accordance with the genetic hypothesis, but were too few in number to provide confirmation.7. The genetic marking of six types of sheep is possible, utilizing the variation in plasma A-esterase activity.

Estimation of the rate of slowly biodegradable COD (SBCOD) hydrolysis under anaerobic, anoxic and aerobic conditions by experiments using starch as model substrate

1995 ◽  
Vol 31 (2) ◽  
pp. 95-103 ◽  
Author(s):  
Takashi Mino ◽  
Delfin C. San Pedro ◽  
Tomonori Matsuo
Keyword(s):  
Activated Sludge ◽  
Biomass Concentration ◽  
Organic Substrate ◽  
Starch Hydrolysis ◽  
Hydrolysis Rate ◽  
Aerobic Conditions ◽  
Hydrolysis Products ◽  
Hydrolysis Rates ◽  
Pure Cultures ◽  
Formation Method

The hydrolysis rates under anaerobic, anoxic and aerobic conditions are studied by using starch as a model organic substrate representing the slowly biodegradable COD. An analytical method, the starch-iodine complex formation method, was introduced to distinguish the polymer starch and its hydrolysis products, and it was applied to estimate the hydrolysis rates in an activated sludge mixed culture, two bacterial pure cultures (Bacillus amyloliquefaciens and Aeromonas hydrophila) or a pure enzyme (α-amylase) system. The rate of starch hydrolysis was found to be independent of the electron acceptor conditions. The starch hydrolysis rate constant of the activated sludge was not affected by the biomass concentration, which indicates that the starch hydrolysis in the activated sludge process follows surface limited adsorption reaction kinetics.

Vinyl ether hydrolysis. XXIV. 1-Methoxycyclooctene and the question of reversibility of the carbon protonation step

1991 ◽  
Vol 69 (1) ◽  
pp. 84-87 ◽  
Author(s):  
A. J. Kresge ◽  
Y. Yin
Keyword(s):  
Reaction Mechanism ◽  
Proton Transfer ◽  
Vinyl Ether ◽  
Isotope Effects ◽  
Hydrolysis Rate ◽  
Hydronium Ion ◽  
Mineral Acids ◽  
Dilute Aqueous Solutions ◽  
Solvent Isotope ◽  
Hydrolysis Of

An argument is presented which suggests that hydrolysis of the vinyl ether group of 1-methoxycyclooctene may occur by reversible proton transfer from a catalyzing acid to the β-carbon atom of the substrate, instead of by the conventional reaction mechanism in which this proton transfer is rate determining and not reversible. Hydrolysis of this substrate is then examined by measuring rates of reaction in dilute aqueous solutions of strong mineral acids (perchloric and hydrochloric) as well as in buffer solutions of seven carboxylic acids, biphosphate ion, and 1,1,1,3,3,3-hexafluoro-2-propanol. General acid catalysis is observed and a Brønsted relation with the exponent α = 0.73 is constructed. That, plus the isotope effects kH/kD = 2.9 and 6.0 for catalysis by hydronium ion and acetic acid respectively, as well as the lack of deuterium incorporation into the substrate when the reaction is carried out in D2O with D2PO4−/DPO42− buffer at pD = 8, show that carbon protonation of the substrate is not reversible and that the conventional reaction mechanism is operative. Key words: 1-methoxycyclooctene, vinyl ether hydrolysis, rate-determining proton transfer, Brønsted relation, solvent isotope effect.

The chemistry of N,N′-dimethylformamidine. II. Hydrolysis. Kinetically controlled formation of cis-N-methylformamide

1978 ◽  
Vol 56 (11) ◽  
pp. 1463-1469 ◽  
Author(s):  
James D. Halliday ◽  
E. Allan Symons
Keyword(s):  
Aqueous Media ◽  
Hydrolysis Rate ◽  
Strong Base ◽  
First Order ◽  
H Nmr ◽  
Stereoelectronic Control ◽  
Pseudo First Order ◽  
Ph Range ◽  
Hydrolysis Of ◽  
Cis Isomer

The hydrolysis of N,N′-dimethylformamidine (DMFA) has been investigated in acid and alkaline aqueous media by 1H nmr; only a narrow basic pH range could be extensively studied kinetically. The pseudo-first-order kobs rose steadily from pH 11.5 to 13.0 (reaction approximately first order in OH−), then became independent of pH above 13.5 (9.3 × 10−4 s−1 at 10 °C). In contrast to many amidines, DMFA is quite stable in acid solution (estimated value of the pseudo-first-order hydrolysis rate constant is 1.4 × 10−1 s−1 at 10 °C, pH 0.05, from measurements at 100 and 140 °C). This stability is ascribed to the difficulty of eliminating the fairly strong base methylamine from the tetrahedral intermediate in acid solution.N-Methylformamide (NMF), one of the products, is formed initially as the cis isomer. A somewhat slower conversion then occurs to the thermodynamically more stable trans isomer. This unusual result is explained in terms of Deslongchamps and co-workers' theory of stereoelectronic control for the orbital-assisted breakdown of tetrahedral intermediates.

Kinetics of aquation and base hydrolysis of the macrocyclic complex trans-Bromo(N-meso-5,12-dimethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene)nitro-cobalt(III) perchlorate

1976 ◽  
Vol 29 (10) ◽  
pp. 2319 ◽  
Author(s):  
GA Lawrance ◽  
RW Hay
Keyword(s):  
Activation Parameters ◽  
Macrocyclic Complex ◽  
Base Hydrolysis ◽  
Hydrolysis Kinetics ◽  
Rate Expression ◽  
Entropy Of Activation ◽  
Ph Range ◽  
Kinetics Of ◽  
Hydrolysis Of

The macrocyclic complex trans-[Co(dtcd)(NO2)Br] [ClO4] (dtcd = 5,12-dimethyl-l,4,8,1l-tetraaza-cyclotetradeca-4,ll-diene) has been prepared and its hydrolysis kinetics investigated. At 25�C and 0.1 M HN03 the aquation occurs with kaq = 6.2 x 10-3 s-1 to give the trans-Co(dtcd)(NO2)- (OH2)]2+ cation. The activation parameters at 298 K are ΔH? = 75.0 kJ mol-1 and ΔS? = -35.6 J K-1 mol-1. Hydrolysis of the bromide in the pH range 7.5-8.8 follows the rate expression kobs = kaq + kOH[OH-]. At 25�C (I = 0.1 M, NaClO4) kOH = 1.21 x 103 1. mol-1 s-1 with the activation parameters for base hydrolysis being ΔH? = 74.2 kJ mol-1 and ΔS? = +63.2 J K-1 mol-1 at 298 K. Aquation and base hydrolysis of the bromo complex at 25�C occur at rates 14 and 5 times faster respectively than those previously reported for the analogous trans-[Co(dtcd)(NO2)Cl]+ complex, the acceleration being due to a more favourable entropy of activation in each case.

scholarly journals Catalytic hydrolysis of CFC-12 over MoO3/ZrO2 -TiO2 solid acid

2020 ◽  
Author(s):  
Zhiqian Li ◽  
Tong Zhou ◽  
Guoqing Ren ◽  
Xiaofang Tan ◽  
Lijuan Jia ◽  
...  
Keyword(s):  
Water Vapor ◽  
Solid Acid ◽  
Hydrolysis Rate ◽  
Vapor Concentration ◽  
Water Vapor Concentration ◽  
Catalytic Hydrolysis ◽  
Hydrolysis Products ◽  
Hydrolysis Temperature ◽  
Continuous Reaction ◽  
Hydrolysis Of

Abstract The catalytic hydrolysis of Difluorodichloromethane(CFC-12) by solid acid of MoO3/ZrO2-TiO2 calcined at different temperature had been studied. The effects of catalytic hydrolysis temperature and water vapor concentration on catalytic hydrolysis of CFC-12were also studied. The results showed that catalytic hydrolysis rate of CFC-12 reached to 98.65% at 400 ℃ when the MoO3/ZrO2-TiO2 catalyst was calcined at 500 ℃ with a concentration of water vapor of 83.18%, and the main hydrolysis products were CO, CO2, HF and HCl. After 30 hours’ continuous reaction, the hydrolysis rate of CFC-12 was 65.34%. The XRD result reveals that the main phase of solid MoO3/ZrO2-TiO2 catalyst is the tetragonal Zr (MoO4)2 with doped TiO2 of anatase.

Alkaline Hydrolysis of Nonphenolic β-0-4 Lignin Models: Substituent Effect of the A-Ring on the Rate

Holzforschung ◽  
2002 ◽  
Vol 56 (6) ◽  
pp. 592-594 ◽  
Author(s):  
T. P. Schultz ◽  
T. H. Fisher
Keyword(s):  
Alkaline Hydrolysis ◽  
Substituent Effect ◽  
Hydrolysis Rate ◽  
Side Reactions ◽  
Hydrolysis Rates ◽  
Hydrolysis Of ◽  
Electron Withdrawing Substituents

Summary Six nonphenolic β-0-4 lignin models substituted on the phenyl A-ring [unsubstituted; 3,5-dimethoxyl; 3,4-dimethoxyl; 3-methoxyl; 4-methoxyl; and 4-methyl] were synthesized and the alkaline hydrolysis rates at 170°C determined. Electron-withdrawing substituents enhanced the hydrolysis rate, but this effect was relatively minor. Over 90% of the disappearance of the dimer could be accounted for by appearance of the B-ring phenolic product for all compounds, which suggests that minimal side reactions occurred.

scholarly journals Study of Hydrolization and Sedimantationin Acid Compositions Based on Sulfaminic Acid

2020 ◽  
Vol 130 (5) ◽  
pp. 32-37
Author(s):  
L. A. Magadova ◽  
◽  
A. N. Sirotin ◽  
M. D. Pakhomov ◽  
Z. R. Davletov ◽  
...  
Keyword(s):  
Hydrochloric Acid ◽  
Calcium Sulfate ◽  
Gravimetric Method ◽  
Sulfamic Acid ◽  
Hydrolysis Rate ◽  
Hydrolysis Products ◽  
Rate Of Hydrolysis ◽  
Quartz Solubility ◽  
Ammonium Sulfamate ◽  
Hydrolysis Of

This article presents the results of a study of the hydrolysis of sulfamic acid and the elaboration of acidic compositions that are characterized by reduced sedimentation compared to mud acid. The effect of complexing compounds on the hydrolysis of sulfamic acid is considered, the hydrolysis of sulfamic acid and sulfamates is compared, and the secondary sedimentation of sulfamic acid and mud acid compositions is compared using the formation of hexafluorosilicates. The hydrolysis intensity of sulfamic acid and ammonium sulfamate was determined by the mass of sediments formed during the reaction of hydrolysis products with calcium chloride. The mass of calcium sulfate formed is proportional to the rate of hydrolysis of sulfamic acid. The process of dissolution of the quartz component of the terrigenous formation was studied using the gravimetric method. Differences in influence of EDTA, HEDP, and NTP on sedimentation prevention of the products of sulfamic acid hydrolysis were studied by the example of reactions with Ca2+. It was shown that compositions with NTP are characterized by a lower sediments formation. The ratio of NTP concentration and the hydrolysis rate of sulfamic acid is shown. Differences in the hydrolysis rate of compositions based on sulfamic acid and sulfamates were determined at a temperature of 80°C. It was shown that sulfamates are characterized by a lower rate of hydrolysis. Differences in quartz solubility were determined for compositions based on sulfamic and sulfuric acids, differences in the reactions kinetics were shown. It has been established that acid compositions based on sulfamic acid are characterized by less sedimentation rate being compared with acid compositions based on hydrochloric acid by the example of hexafluorosilicates formation.

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