Vinyl ether hydrolysis. XVII. Oxacyclonon-2,8-diene and the question of the unorthodox reaction mechanism for 9-methoxyoxacyclonon-2-ene

1984 ◽  
Vol 62 (1) ◽  
pp. 74-76 ◽  
Author(s):  
R. A. Burt ◽  
Y. Chiang ◽  
A. J. Kresge ◽  
S. Szilagyi
Keyword(s):  
Reaction Mechanism ◽  
Vinyl Ether ◽  
Membered Ring ◽  
Specific Rate ◽  
Ether Group ◽  
Reaction Proceeds ◽  
Great Reactivity ◽  
Rate Of Hydrolysis ◽  
Acid Catalyzed ◽  
Hydrolysis Of

The acid-catalyzed hydrolysis of the nine-membered ring cyclic vinyl ether, oxacyclonon-2,8-diene, occurs with a normal isotope effect, [Formula: see text], which indicates that this reaction proceeds by the conventional vinyl ether hydrolysis mechanism involving rate-determining proton transfer to carbon. The specific rate of this reaction, [Formula: see text], may then be used to show that there is no significant ring-size effect on the rate of hydrolysis of a vinyl ether group in a nine-membered ring. The previously noted unusually great reactivity of the vinyl ether group in 9-methoxyoxacyclonon-2-ene, for which an unorthodox reaction mechanism has been claimed, must therefore be due to some other cause.

scholarly journals Acid-catalyzed hydrolysis of the vinyl ether group of 4-methoxy-1,2-dihydronaphthalene. Effect of conformation on reactivity

ARKIVOC ◽  
2001 ◽  
Vol 2002 (4) ◽  
pp. 12-17
Author(s):  
A. Awwal ◽  
W. E. Jones ◽  
A. J. Kresge ◽  
Q. Meng
Keyword(s):  
Vinyl Ether ◽  
Ether Group ◽  
Acid Catalyzed ◽  
Hydrolysis Of

The effect of polymeric and model imidazolium halides on the rate of hydrolysis of 4-acetoxy-3-nitrobenzoic acid

1985 ◽  
Vol 50 (4) ◽  
pp. 845-853 ◽  
Author(s):  
Miloslav Šorm ◽  
Miloslav Procházka ◽  
Jaroslav Kálal
Keyword(s):  
Catalyst Concentration ◽  
Low Molecular Weight ◽  
Imidazolium Chloride ◽  
First Order ◽  
Nitrobenzoic Acid ◽  
Rate Of Hydrolysis ◽  
Acid Catalyzed ◽  
Hydrolysis Of ◽  
Ethanol In Water ◽  
Direct Attack

The course of hydrolysis of an ester, 4-acetoxy-3-nitrobenzoic acid catalyzed with poly(1-methyl-3-allylimidazolium bromide) (IIa), poly[l-methyl-3-(2-propinyl)imidazolium chloride] (IIb) and poly[l-methyl-3-(2-methacryloyloxyethyl)imidazolium bromide] (IIc) in a 28.5% aqueous ethanol was investigated as a function of pH and compared with low-molecular weight models, viz., l-methyl-3-alkylimidazolium bromides (the alkyl group being methyl, propyl, and hexyl, resp). Polymers IIb, IIc possessed a higher activity at pH above 9, while the models were more active at a lower pH with a maximum at pH 7.67. The catalytic activity at the higher pH is attributed to an attack by the OH- group, while at the lower pH it is assigned to a direct attack of water on the substrate. The rate of hydrolysis of 4-acetoxy-3-nitrobenzoic acid is proportional to the catalyst concentration [IIc] and proceeds as a first-order reaction. The hydrolysis depends on the composition of the solvent and was highest at 28.5% (vol.) of ethanol in water. The hydrolysis of a neutral ester, 4-nitrophenyl acetate, was not accelerated by IIc.

THE CHEMISTRY OF ETHYLENE OXIDE: V. THE REACTION OF ETHYLENE OXIDE WITH HALIDE IONS IN NEUTRAL AND ACID SOLUTION

1952 ◽  
Vol 30 (3) ◽  
pp. 169-176 ◽  
Author(s):  
A. M. Eastham ◽  
G. A. Latremouille
Keyword(s):  
Aqueous Solution ◽  
Ethylene Oxide ◽  
Acid Solution ◽  
Activation Energies ◽  
Hydrogen Halide ◽  
Halide Ions ◽  
Neutral Aqueous Solution ◽  
Rate Of Hydrolysis ◽  
Acid Catalyzed ◽  
Hydrolysis Of

The rates of reaction of halide ions with ethylene oxide in neutral aqueous solution and the rate of hydrolysis of ethylene oxide in acid solution have been measured and the activation energies determined. From these data and from the ratio of glycol to chlorohydrin formed when ethylene oxide reacts with excess aqueous hydrogen halide, the rates of the acid-catalyzed addition of halide ions to ethylene oxide at 25 °C. have been estimated.

THE ACID HYDROLYSIS OF GLYCOSIDES: I. GENERAL CONDITIONS AND THE EFFECT OF THE NATURE OF THE AGLYCONE

1964 ◽  
Vol 42 (6) ◽  
pp. 1456-1472 ◽  
Author(s):  
T. E. Timell
Keyword(s):  
Acid Hydrolysis ◽  
Equilibrium Concentration ◽  
Rate Coefficients ◽  
Acidity Function ◽  
Tertiary Alcohols ◽  
Conjugate Acid ◽  
Rate Of Hydrolysis ◽  
Acid Catalyzed ◽  
Opposing Effects ◽  
Hydrolysis Of

First-order rate coefficients and energies and entropies of activation have been determined for the acid-catalyzed hydrolysis of a number of methyl D-glycopyranosides and disaccharides. The relation between the logarithm of the rate coefficients and values for Hammett's acidity function was linear, although different for different acids. All compounds had entropies of activation indicating a unimolecular reaction mechanism. Glucosides of tertiary alcohols were hydrolyzed very rapidly, triethylmethyl β-D-glucopyranoside, for example, 30,000 times taster than the corresponding methyl compound.Increase in size of the aglycone caused a slight increase in the rate of hydrolysis of β-D-glucopyranosides, steric hindrance thus being of no significance. Electron-attracting substituents in the aglycone had little or no influence on the rate of hydrolysis, obviously because they would tend to lower the equilibrium concentration of the conjugate acid, while facilitating the subsequent heterolysis, the two opposing effects more or less cancelling out. These results were discussed in connection with recent studies on the acid hydrolysis of various phenyl glycopyranosides and with reference to the postulated occurrence of an activating inductive effect in oligo- and poly-saccharides containing carboxyl or other electronegative groups at C-5. It was concluded that there is little evidence for the existence of any such effect and that, for example, pseudoaldobiouronic acids should be hydrolyzed at the same rate as corresponding neutral disaccharides.

A Raman Spectral Study of the Kinetics of Hydrolysis of Acetonitrile Catalyzed by Hg(II)

1975 ◽  
Vol 53 (3) ◽  
pp. 427-436 ◽  
Author(s):  
Yu-Keung Sze ◽  
Donald E. Irish
Keyword(s):  
Time Span ◽  
Water Molecules ◽  
Specific Rate ◽  
Ammine Complexes ◽  
Kinetics Of Hydrolysis ◽  
Specific Rate Constant ◽  
Rate Of Hydrolysis ◽  
Raman Spectral ◽  
Kinetics Of ◽  
Hydrolysis Of

Raman spectroscopy has been employed to follow the relatively slow rate of hydrolysis of acetonitrile, catalyzed by mercury(II). Raman lines at 2275 and 2305 cm−1 are characteristic of CH3CN bound to Hg2+, and are distinct from lines of bulk solvent. The intensities of these new lines decrease with time. From the intensities, concentrations of bound acetonitrile, [CH3CN]B were calculated for a time span of 400 min. The data fit a second order rate law: Rate = k[CH3CN]B[H2O]. The specific rate constant, k, obtained from four sets of data for the system Hg(ClO4)2–CH3CN–H2O equals 1.05 ± 0.06 × 10−4 mol−1 1 min−1 at 25 °C. The energy of activation is 18.9 kcal mol−1. In the proposed mechanism water molecules attack acetonitrile molecules which are bound to Hg2+ and form a mercury(II)–acetamide complex. Raman lines characteristic of this species are observed. This species slowly converts to mercury(II) ammine complexes and acetic acid. Anions which coordinate with Hg2+ more strongly than CH3CN, such as nitrate or acetate, slow or prevent the hydrolysis reaction.

scholarly journals The reaction of alkylating agents with bacteriophage R17. Biological effects of phosphotriester formation

1974 ◽  
Vol 137 (2) ◽  
pp. 313-317 ◽  
Author(s):  
Kenneth V. Shooter ◽  
Ruth Howse ◽  
R. Kenneth Merrifield
Keyword(s):  
Reaction Mechanism ◽  
Biological Effects ◽  
Alkylating Agents ◽  
Hydrolysis Reaction ◽  
Ethyl Methanesulphonate ◽  
Neutral Ph ◽  
Rate Of Hydrolysis ◽  
Alkylation Reactions ◽  
Kinetics Of ◽  
Hydrolysis Of

The extent of biological inactivation and of the degradation of the RNA after reaction of bacteriophage R17 with ethyl methanesulphonate, isopropyl methanesulphonate and N-ethyl-N-nitrosourea was studied. Formation of breaks in the RNA chain probably results from hydrolysis of phosphotriesters formed in the alkylation reactions. Near neutral pH the ethyl and isopropyl phosphotriesters are sufficiently stable for the kinetics of the hydrolysis reaction to be followed. Results indicate that the rate of hydrolysis increases rapidly as the pH is raised. The evidence shows that a phosphotriester group does not itself constitute a lethal lesion. The extent of phosphotriester formation by the different agents is discussed in terms of reaction mechanism.

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 HYDROLYSIS OF THE CONDENSED PHOSPHATES: III. SODIUM TETRAMETAPHOSPHATE AND SODIUM TETRAPHOSPHATE

1956 ◽  
Vol 34 (7) ◽  
pp. 969-981 ◽  
Author(s):  
Joan Crowther ◽  
A. E. R. Westman
Keyword(s):  
Phosphate Glass ◽  
Sodium Phosphate ◽  
Hydrogen Ion ◽  
Ion Concentrations ◽  
First Order ◽  
Condensed Phosphates ◽  
Rate Of Hydrolysis ◽  
Acid Catalyzed ◽  
Ph Range ◽  
Hydrolysis Of

The rates of hydrolysis of sodium tetrametaphosphate and tetraphosphate (in the presence of tetrametaphosphate) have been measured at 65.5 °C. over the pH range 2.5 to 13.3. Tetrametaphosphate anions hydrolyze to tetraphosphate which in turn hydrolyzes to triphosphate and orthophosphate and not to pyrophosphate. Thus the terminal oxygen bridges in the tetraphosphate and not the central one are attacked preferentially. The reactions were first order and acid catalyzed. The tetrametaphosphate hydrolysis was also base catalyzed with a minimum rate in solutions of pH approximately 7.5. The rate of hydrolysis of tetraphosphate was greater than triphosphate at the hydrogen ion concentrations studied. Hydrolysis of a sodium phosphate glass indicated that preferential attack on terminal oxygen bridges takes place also with higher polymers. However, trimetaphosphate is formed at the same time.

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