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.

ChemInform Abstract: VINYL ETHER HYDROLYSIS. 9. ISOTOPE EFFECTS ON PROTON TRANSFER FROM THE HYDRONIUM ION

1978 ◽  
Vol 9 (5) ◽  
Author(s):  
A. J. KRESGE ◽  
D. S. SAGATYS ◽  
H. L. CHEN
Keyword(s):  
Proton Transfer ◽  
Vinyl Ether ◽  
Isotope Effects ◽  
Hydronium Ion

Vinyl ether hydrolysis. 9. Isotope effects on proton transfer from the hydronium ion

1977 ◽  
Vol 99 (22) ◽  
pp. 7228-7233 ◽  
Author(s):  
A. J. Kresge ◽  
D. S. Sagatys ◽  
H. L. Chen
Keyword(s):  
Proton Transfer ◽  
Vinyl Ether ◽  
Isotope Effects ◽  
Hydronium Ion

Vinyl ether hydrolysis. XXIX. 1-Methoxy-1,3-butadiene: reaction mechanism and implication for hydrolysis of the mutagen fecapentaene-12

1994 ◽  
Vol 72 (7) ◽  
pp. 1632-1636 ◽  
Author(s):  
Yvonne Chiang ◽  
Robert Eliason ◽  
Gary H.-X. Guo ◽  
A. Jerry Kresge
Keyword(s):  
Vinyl Ether ◽  
Trans Isomer ◽  
Acid Catalysis ◽  
Isotope Effects ◽  
Hydronium Ion ◽  
Rapid Formation ◽  
Methyl Vinyl Ether ◽  
Cis And Trans ◽  
Hydrolysis Of ◽  
Cis Isomer

The hydrolysis of cis- and trans-1-methoxy-1,3-butadiene in aqueous solution occurs by hydron transfer to the δ-carbon atom with little or no β-hydronation to give crotonaldehyde as essentially the sole aldehyde product. The reaction gives appreciable hydronium-ion isotope effects in the normal direction [Formula: see text] and shows general acid catalysis; five carboxylic acid catalytic coefficients for hydrolysis of the trans isomer give a good Brønsted relation with the exponent α = 0.59. This is taken as evidence that these reactions occur by the conventional mechanism for vinyl ether hydrolysis involving rate-determining hydron transfer to substrate carbon followed by rapid formation and decomposition of a hemiacetal intermediate. Comparison of the reactivity of the present dienyl ethers with that of their monoenyl analog, methyl vinyl ether, shows that introduction of the second double bond decreases reactivity considerably: the hydronium-ion catalytic coefficient is reduced by a factor of 8.3 for the trans isomer and by a factor of 160 for the cis isomer. This reduction supports a hypothesis advanced to explain the occurrence of reaction by a different mechanism recently discovered in the hydrolysis of the strongly mutagenic polyenyl ether, fecapentaene-12.

Vinyl ether hydrolysis XXVIII. The mechanism of reaction of methyl α-(2,6-dimethoxyphenyl)vinyl ether

1993 ◽  
Vol 71 (1) ◽  
pp. 38-41 ◽  
Author(s):  
J. Jones ◽  
A. J. Kresge
Keyword(s):  
Vinyl Ether ◽  
Nucleophilic Attack ◽  
Tracer Study ◽  
Solvent Isotope Effect ◽  
Methyl Group ◽  
Hydronium Ion ◽  
Mechanism Of Reaction ◽  
Acid Catalyzed ◽  
Solvent Isotope ◽  
Hydrolysis Of

The acid-catalyzed hydrolysis of methyl α-(2,6-dimethoxyphenyl)vinyl ether in aqueous solution at 25 °C occurs with the hydronium ion catalytic coefficient [Formula: see text] and gives the solvent isotope effect [Formula: see text] this indicates that reaction occurs by rate-determining proton transfer from the catalyst to the substrate to generate an alkoxycarbocation intermediate. An oxygen-18 tracer study shows further that, despite the steric hindrance provided by its two ortho substituents, this cation then reacts by addition of water to the cationic carbon atom to generate a hemiacetal, and not by nucleophilic attack of water on the methyl group remote from the carbocationic center:[Formula: see text]

Solvent isotope effects upon proton transfer from the hydronium ion

1971 ◽  
Vol 93 (1) ◽  
pp. 9-20 ◽  
Author(s):  
Rory A. More O'Ferrall ◽  
Gerald W. Koeppl ◽  
A. Jerry Kresge
Keyword(s):  
Proton Transfer ◽  
Isotope Effects ◽  
Hydronium Ion ◽  
Solvent Isotope ◽  
Solvent Isotope Effects

scholarly journals Vinyl ether hydrolysis. XXIII. Solvent isotope effect on the reaction of divinyl ether catalyzed by the hydronium ion

1990 ◽  
Vol 68 (12) ◽  
pp. 2129-2130 ◽  
Author(s):  
A. J. Kresge ◽  
M. Leibovitch
Keyword(s):  
Vinyl Ether ◽  
Isotope Effect ◽  
Perchloric Acid ◽  
Divinyl Ether ◽  
Solvent Isotope Effect ◽  
Hydronium Ion ◽  
Solvent Isotope ◽  
Hydrolysis Of

Rates of hydrolysis of divinyl ether (CH2=CHOCH=CH2), measured in dilute H2O and D2O solutions of perchloric acid at 25 °C, provide the catalytic coefficients kH+ = 0.0084 M−1 s−1 and kD+ = 0.0028 M−1 s−1, and these lead to the isotope effect kH/kD = 3.0. The magnitude of this isotope effect indicates that this reaction occurs by rate-determining hydron transfer from catalyst to substrate and thus follows the conventional mechanism for vinyl ether hydrolysis. Keywords: divinyl ether, vinyl ether hydrolysis, solvent isotope effect.

Kinetics and mechanism of acid-catalyzed hydrolysis of the diazo functional groups of 1-diazo-2-indanone and 2-diazo-1-indanone in aqueous solution

2005 ◽  
Vol 83 (9) ◽  
pp. 1202-1206 ◽  
Author(s):  
Yvonne Chiang ◽  
A Jerry Kresge ◽  
Oleg Sadovski ◽  
Xiaofeng Zeng ◽  
Yu Zhu
Keyword(s):  
Formic Acid ◽  
Isotope Effect ◽  
Isotope Effects ◽  
Diazo Compound ◽  
Acid Buffer ◽  
Buffer Solutions ◽  
Hydronium Ion ◽  
Solvent Isotope ◽  
Hydrolysis Of ◽  
Solvent Isotope Effects

Rates of hydrolysis of 1-diazo-2-indanone and 2-diazo-1-indanone were measured in dilute aqueous perchloric acid solutions using both H2O and D2O as the solvent, and rates of hydrolysis of the latter substrate were measured in dilute aqueous (H2O only) formic acid buffer solutions as well. The data for 1-diazo-2-indanone gave the hydronium ion catalytic coefficient kH+ = 5.7 × 10–3 (mol/L)–1 s–1 and the isotope effect kH+/kD+ = 2.9. The normal direction (kH/kD > 1) of this isotope effect was taken as evidence for a reaction mechanism involving rate-determining hydron transfer from the hydronium ion to the substrate's diazo carbon atom; followed by rapid displacement of diazo nitrogen by a water molecule, giving the observed 1-hydroxy-2-indanone product. The data for 2-diazo-1-indanone, on the other hand, gave a hydronium ion catalytic coefficient two orders of magnitude greater than the value for 1-diazo-2-indanone (kH+ = 5.9 × 10–1 (mol/L)–1 s–1), and an isotope effect near unity (kH+/kD+ = 1.2). It is argued that this isotope effect represents a situation in which diazo carbon hydronation and displacement of diazo nitrogen are each partly rate determining, a conclusion supported by incipient saturation of buffer catalysis in the formic acid buffer solutions. The 100-fold difference in hydronium ion catalytic coefficients for the two substrates is rationalized in terms of differing electron densities on the diazo carbon atoms.Key words: diazo compound hydrolysis, solution kinetics, acid catalysis, solvent isotope effects, buffer catalysis saturation.

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.

Vinyl ether hydrolysis. XIII. The failure of I-strain to produce a change in rate-determining step

1980 ◽  
Vol 58 (2) ◽  
pp. 124-129 ◽  
Author(s):  
Y. Chiang ◽  
W. K. Chwang ◽  
A. J. Kresge ◽  
S. Szilagyi
Keyword(s):  
Vinyl Ether ◽  
Acid Catalysis ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Mineral Acid ◽  
Buffer Solutions ◽  
Rate Determining Step ◽  
Kinetic Isotope ◽  
Acetic Acid Buffer ◽  
Hydrolysis Of

Rates of hydrolysis of 1-ethoxy-3,3,5,5-tetramethylcyclopentene and 1-methoxy-2,3,3,5,5-pentamethylcyclopentene measured in mineral acid and formic and acetic acid buffer solutions show general acid catalysis and give large kinetic isotope effects in the normal direction (kH/kD > 1). This indicates that these reactions proceed by the conventional mechanism for vinyl ether hydrolysis in which proton transfer from the catalyzing acid to the substrate is rate-determining, and that the I-strain in these substrates is insufficiently great to shift the reaction mechanism to rapidly reversible substrate protonation followed by rate-determining hydration of the ensuing cationic intermediate.

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