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.

scholarly journals Hydrolysis of Dimethyl Methylphosphonate (DMMP) in Hot-Compressed Water

2020 ◽  
Author(s):  
Brian Pinkard ◽  
Shreyas Shetty ◽  
John Kramlich ◽  
Per G. Reinhall ◽  
Igor V. Novosselov
Keyword(s):  
Hydrolysis Rate ◽  
Methylphosphonic Acid ◽  
Practical Implementation ◽  
Reaction Products ◽  
Dimethyl Methylphosphonate ◽  
Exponential Factor ◽  
First Order ◽  
Pseudo First Order ◽  
Hot Compressed Water ◽  
Hydrolysis Of

<p>Dimethyl methylphosphonate (DMMP) is widely used as a chemical surrogate for G- and V-type nerve agents, exhibiting similar physiochemical properties, yet significantly lower toxicity. Continuous hydrolysis of DMMP in hot-compressed water is performed at temperatures from 200 to 300 °C, pressures of 20 and 30 MPa, and residence times from 30 to 80 s to evaluate the effects of pressure and temperature on reaction kinetics. DMMP hydrolysis is observed to follow pseudo-first-order reaction behavior, producing methylphosphonic acid and methanol as the only detectable reaction products. This is significant for the practical implementation of a continuous hydrothermal reactor for chemical warfare agent neutralization, as the process only yields stable, less-toxic compounds. Pressure has no discernible effect on the hydrolysis rate in compressed liquid water. Pseudo-first-order Arrhenius parameters are determined, with an activation energy of<i> </i>90.17±5.68<i> </i>kJ mol<sup>-1</sup> and a pre-exponential factor of 10<sup>7.51</sup><sup>±0.58</sup> s<sup>-1</sup>.<br></p>

scholarly journals Hydrolysis of Dimethyl Methylphosphonate (DMMP) in Hot-Compressed Water

2020 ◽  
Author(s):  
Brian Pinkard ◽  
Shreyas Shetty ◽  
John Kramlich ◽  
Per G. Reinhall ◽  
Igor V. Novosselov
Keyword(s):  
Hydrolysis Rate ◽  
Methylphosphonic Acid ◽  
Practical Implementation ◽  
Reaction Products ◽  
Dimethyl Methylphosphonate ◽  
Exponential Factor ◽  
First Order ◽  
Pseudo First Order ◽  
Hot Compressed Water ◽  
Hydrolysis Of

<p>Dimethyl methylphosphonate (DMMP) is widely used as a chemical surrogate for G- and V-type nerve agents, exhibiting similar physiochemical properties, yet significantly lower toxicity. Continuous hydrolysis of DMMP in hot-compressed water is performed at temperatures from 200 to 300 °C, pressures of 20 and 30 MPa, and residence times from 30 to 80 s to evaluate the effects of pressure and temperature on reaction kinetics. DMMP hydrolysis is observed to follow pseudo-first-order reaction behavior, producing methylphosphonic acid and methanol as the only detectable reaction products. This is significant for the practical implementation of a continuous hydrothermal reactor for chemical warfare agent neutralization, as the process only yields stable, less-toxic compounds. Pressure has no discernible effect on the hydrolysis rate in compressed liquid water. Pseudo-first-order Arrhenius parameters are determined, with an activation energy of<i> </i>90.17±5.68<i> </i>kJ mol<sup>-1</sup> and a pre-exponential factor of 10<sup>7.51</sup><sup>±0.58</sup> s<sup>-1</sup>.<br></p>

In-vitro Kinetic Hydrolysis Study of Metronidazole Derivatives with Carvacrol and Eugenol Using Validated RP-HPLC Method

2020 ◽  
Vol 16 ◽  
Author(s):  
M. Alarjah
Keyword(s):  
Half Life ◽  
Hplc Method ◽  
Hydrolysis Rate ◽  
First Order ◽  
First Order Kinetics ◽  
Rp Hplc ◽  
Pharmacokinetic Properties ◽  
Pseudo First Order ◽  
Kinetic Hydrolysis

Background: Prodrugs principle is widely used to improve the pharmacological and pharmacokinetic properties of some active drugs. Much effort was made to develop metronidazole prodrugs to enhance antibacterial activity and or to improve pharmacokinetic properties of the molecule or to lower the adverse effects of metronidazole. Objective: In this work, the pharmacokinetic properties of some of monoterpenes and eugenol pro metronidazole molecules that were developed earlier were evaluated in-vitro. The kinetic hydrolysis rate constants and half-life time estimation of the new metronidazole derivatives were calculated using the validated RP-HPLC method. Method: Chromatographic analysis was done using Zorbbax Eclipse eXtra Dense Bonding (XDB)-C18 column of dimensions (250 mm, 4.6 mm, 5 μm), at ambient column temperature. The mobile phase was a mixture of sodium dihydrogen phosphate buffer of pH 4.5 and methanol in gradient elution, at 1ml/min flow rate. The method was fully validated according to the International Council for Harmonization (ICH) guidelines. The hydrolysis process carried out in an acidic buffer pH 1.2 and in an alkaline buffer pH 7.4 in a thermostatic bath at 37ºC. Results: The results followed pseudo-first-order kinetics. All metronidazole prodrugs were stable in the acidic pH, while they were hydrolysed in the alkaline buffer within a few hours (6-8 hr). The rate constant and half-life values were calculated, and their values were found to be 0.082- 0.117 hr-1 and 5.9- 8.5 hr., respectively. Conclusion: The developed method was accurate, sensitive, and selective for the prodrugs. For most of the prodrugs, the hydrolysis followed pseudo-first-order kinetics; the method might be utilised to conduct an in-vivo study for the metronidazole derivatives with monoterpenes and eugenol.

scholarly journals MW irradiation and ionic liquids as green tools in hydrolyses and alcoholyses

2020 ◽  
Vol 10 (1) ◽  
pp. 001-010 ◽  
Author(s):  
Nikoletta Harsági ◽  
Betti Szőllősi ◽  
Nóra Zsuzsa Kiss ◽  
György Keglevich
Keyword(s):  
Ionic Liquids ◽  
Alkaline Hydrolysis ◽  
Alkyl Group ◽  
Phosphinic Acid ◽  
Reaction Times ◽  
Alternative Possibility ◽  
First Order ◽  
Pseudo First Order ◽  
Mw Irradiation ◽  
Hydrolysis Of

Abstract The optimized HCl-catalyzed hydrolysis of alkyl diphenylphosphinates is described. The reaction times and pseudo-first-order rate constants suggested the iPr > Me > Et ∼ Pr ∼ Bu order of reactivity in respect of the alkyl group of the phosphinates. The MW-assisted p-toluenesulfonic acid (PTSA)-catalyzed variation means a better alternative possibility due to the shorter reaction times, and the alkaline hydrolysis is another option. The transesterification of alkyl diphenylphosphinates took place only in the presence of suitable ionic liquids, such as butyl-methylimidazolium hexafluorophosphorate ([bmim][PF6]) and butyl-methylimidazolium tetrafluoroborate ([bmim][BF4]). The application of ethyl-methylimidazolium hydrosulfate ([emim][HSO4]) and butyl-methylimidazolium chloride ([bmim][Cl]) was not too efficient, as the formation of the ester was accompanied by the fission of the O–C bond resulting in the formation of Ph2P(O)OH. This surprising transformation may be utilized in the phosphinate → phosphinic acid conversion.

A kinetic standard for precise calibration of spectrophotometer cell temperature.

1981 ◽  
Vol 27 (5) ◽  
pp. 753-755 ◽  
Author(s):  
P A Adams ◽  
M C Berman
Keyword(s):  
Temperature Dependence ◽  
Rate Constants ◽  
Cell Temperature ◽  
First Order ◽  
Order Rate ◽  
Acid Catalyzed ◽  
Pseudo First Order ◽  
Hydrolysis Of

Abstract We describe a simple, highly reproducible kinetic technique for precisely measuring temperature in spectrophotometric systems having reaction cells that are inaccessible to conventional temperature probes. The method is based on the temperature dependence of pseudo-first-order rate constants for the acid-catalyzed hydrolysis of N-o-tolyl-D-glucosylamine. Temperatures of reaction cuvette contents are measured with a precision of +/- 0.05 degrees C (1 SD).

Acid-catalyzed Solvolysis of Isonitriles. I

1971 ◽  
Vol 49 (14) ◽  
pp. 2455-2459 ◽  
Author(s):  
Y. Y. Lim ◽  
A. R. Stein
Keyword(s):  
Formic Acid ◽  
Acid Catalysis ◽  
Hydrolysis Product ◽  
Rate Dependence ◽  
Linear Rate ◽  
First Order ◽  
Methyl Amine ◽  
Acid Catalyzed ◽  
Pseudo First Order ◽  
Hydrolysis Of

The acid-catalyzed hydrolysis of methyl isonitrile has been examined. The initial hydrolysis product is N-methylformamide which is further hydrolyzed to methyl amine and formic acid at a much slower rate. The hydrolysis to N-methylformamide is pseudo-first order in methyl isonitrile and shows a linear rate dependence on concentration of general (buffer) acid at fixed pH. The significance of general acid-catalysis in terms of the mechanism of the hydrolysis is considered and taken as evidence for carbon protonation rather than nitrogen protonation as the initiating step.

scholarly journals Hydrolysis of Methionine- and Histidine-Containing Peptides Promoted by Dinuclear Platinum(II) Complexes with Benzodiazines as Bridging Ligands: Influence of Ligand Structure on the Catalytic Ability of Platinum(II) Complexes

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Snežana Rajković ◽  
Beata Warżajtis ◽  
Marija D. Živković ◽  
Biljana Đ. Glišić ◽  
Urszula Rychlewska ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Amide Bond ◽  
Spectroscopic Techniques ◽  
X Ray Diffraction ◽  
Bridging Ligands ◽  
Metal Centers ◽  
H Nmr ◽  
Dinuclear Platinum ◽  
Ph Range ◽  
Hydrolysis Of

Dinuclear platinum(II) complexes, [{Pt(en)Cl}2(μ-qx)]Cl2·2H2O (1), [{Pt(en)Cl}2(μ-qz)](ClO4)2(2), and [{Pt(en)Cl}2(μ-phtz)]Cl2·4H2O (3), were synthesized and characterized by different spectroscopic techniques. The crystal structure of1was determined by single-crystal X-ray diffraction analysis, while the DFT M06-2X method was applied in order to optimize the structures of1–3. The chlorido Pt(II) complexes1–3were converted into the corresponding aqua species1a–3a, and their reactions with an equimolar amount of Ac–L–Met–Gly and Ac–L–His–Gly dipeptides were studied by1H NMR spectroscopy in the pH range 2.0 < pH < 2.5 at 37°C. It was found that, in all investigated reactions with the Ac–L–Met–Gly dipeptide, the cleavage of the Met–Gly amide bond had occurred, but complexes2aand3ashowed lower catalytic activity than1a. However, in the reactions with Ac–L–His–Gly dipeptide, the hydrolysis of the amide bond involving the carboxylic group of histidine was observed only with complex1a. The observed disparity in the catalytic activity of these complexes is thought to be due to different relative positioning of nitrogen atoms in the bridging qx, qz, and phtz ligands and consequent variation in the intramolecular separation of the two platinum(II) metal centers.

Evidence for the formation of lignin-hexenuronic acid-xylan complexes during modified kraft pulping processes

Holzforschung ◽  
2006 ◽  
Vol 60 (2) ◽  
pp. 137-142 ◽  
Author(s):  
Zhi-Hua Jiang ◽  
Jean Bouchard ◽  
Richard Berry
Keyword(s):  
Acid Hydrolysis ◽  
Kraft Pulp ◽  
Kraft Pulping ◽  
Order Kinetic ◽  
Kraft Pulps ◽  
First Order ◽  
Pseudo First Order ◽  
Hexenuronic Acid ◽  
Kinetics Of ◽  
Hydrolysis Of

Abstract The finding that hexenuronic acid (HexA) groups can be selectively removed from kraft pulps by acid hydrolysis has provided an opportunity to reduce bleaching chemicals. However, there is evidence that the acid hydrolysis is not uniform. In this report, we evaluate the kinetics of acid hydrolysis of HexA in a xylan sample enriched with HexA, a conventional kraft pulp, and three modified kraft pulps: anthraquinone pulp (Kraft-AQ), polysulfide pulp (PS), and polysulfide-anthraquinone pulp (PS-AQ). We found that HexA present in the xylan and conventional kraft pulp behaved similarly toward the acid hydrolysis throughout. On the other hand, HexA present in the Kraft-AQ, PS-AQ and PS pulps was heterogeneous toward acid hydrolysis and the reaction can be separated into two pseudo-first-order kinetic phases, each of which has a different rate constant. The kinetic data provide evidence for the formation of lignin-HexA-xylan complexes during modified kraft pulping processes.

Electron-Transfer Reactions in Non-Aqueous Media. V. Solvent Effects in the Reduction of CoN3(NH3)52+ by Iron(II)

1979 ◽  
Vol 32 (10) ◽  
pp. 2139 ◽  
Author(s):  
TJ Westcott ◽  
DW Watts
Keyword(s):  
Electron Transfer ◽  
Aqueous Media ◽  
Activation Parameters ◽  
Transfer Reactions ◽  
Tetrahedral Coordination ◽  
First Order ◽  
Precursor Complex ◽  
Stage Process ◽  
Pseudo First Order ◽  
Reversible Formation

The reduction of CoN3(NH3)52+ by iron(II) is rate-determined by a two-stage process involving the reversible formation of an azide-bridged precursor complex prior to electron transfer in each of the solvents water, Me2SO, aqueous Me2SO and HCONMe2. The activation parameters in H2O and Me2SO, and the trends shown with increasing Me2SO concentrations in aqueous Me2SO, are similar to the properties of the previously studied CoCl(NH3)52+ and CoBr(NH3)52+ systems and contrast with the reduction of COF(NH3)52+. The results are consistent with a bridged precursor complex octahedral at both the iron and cobalt atoms in water but with tetrahedral coordination about the iron in Me2SO. In HCONMe2, as in the reduction of COF(NH3)52+, COCl(NH3)52+ and COBr(NH3)52+, the precursor complex is a significant part of the reacting solutions, and as a result the experimental pseudo-first-order rate constants for the loss of CoIII are not linearly dependent on the concentration of FeII. The initial spectra of the reacting solutions in this system also indicate significant concentrations of the precursor complex.

Base hydrolysis of trans-Halogenoamminebis(dimethylglyoximato) (III). Complexes

1969 ◽  
Vol 22 (12) ◽  
pp. 2569 ◽  
Author(s):  
SC Chan ◽  
PY Leung
Keyword(s):  
Equilibrium Constants ◽  
Base Hydrolysis ◽  
Hydroxide Ion ◽  
First Order ◽  
Rate Determining Step ◽  
Rapid Formation ◽  
Pseudo First Order ◽  
Conjugate Bases ◽  
Hydrolysis Of ◽  
Conjugate Base

The disappearance of trans-[Co(LH)2(NH3)X] (LH = dimethylglyoximate ion, X = chloride or bromide) has been studied in aqueous solutions over a range of alkali concentrations at various temperatures. The kinetics were done with excess of hydroxide ion at a constant ionic strength so that pseudo first-order rate constants were obtained in all the runs. The results were interpreted in terms of the rapid formation of a pre- equilibrium species which then reacts in a rate-determining step to give products. The relatively large equilibrium constants support a conjugate-base pre-equilibrium, in which the proton is lost from oxygen, while the relatively low reactivities of the conjugate-bases are consistent with the absence of electropositive electromeric effects. The similarity in the reactivities of the chloro and the bromo conjugate-bases suggests the possibility of an SN2CB mechanism.

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