Vinyl Ether Hydrolysis Research Articles

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

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.

Evidence for intramolecular electrostatic catalysis as a possible mechanism in the hydrolysis of vinyl ethers in aqueous solution

The hydrolysis of the vinyl ether functional group in 2-methoxybicyclo [2.2.2] oct-2-ene-1-carboxylic acid has been found to be catalyzed by intramolecular electrostatic catalysis by the carboxylate ion of the substrate. The rate constant ratios of the charged and the neutral form of the substrate are 32.3 and 31.2 for catalysis by hydronium ion and acetic acid, respectively. This is in contrast to ratios that have been found for vinyl ethers hydrolyzed by intramolecular general-acid catalysis, where large rate ratios for catalysis by hydronium ion but small rate ratios, normally a factor 2, when catalyzed by acetic acid are observed. The solvent isotope effect, 3.4±0.5, is close to what has been predicted for electrostatic catalysis in the hydrolysis of prostacyclin

There is no evidence for electrostatic catalysis of vinyl ether hydrolysis in water

The apparent catalysis by the neighbouring carboxylate group in the acid-catalysed hydrolysis of 2-methoxybicyclo[2.2.2]octene-1-carboxylate 1 is accounted for by the change in inductive effect on ionisation of the CO2H group.

Efficient intramolecular general acid catalysis of vinyl ether hydrolysis by the neighbouring carboxylic acid group

Intramolecular catalysis by the CO2H group of the hydrolysis of E-1-methoxy-2-(2-carboxyphenyl)ethylene 5, shows an effective molarity of almost 300 M, the highest measured for intramolecular proton transfer to carbon.

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

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.

Acid-catalyzed hydrolysis of tetramethoxyethene in aqueous solution. Initial state stabilization by the methoxy groups

The acid-catalyzed hydrolysis of tetramethoxyethene to methyl dimethoxyacetate in aqueous solution at 25 °C was found to occur with the hydronium-ion catalytic coefficient [Formula: see text], to give the solvent isotope effect [Formula: see text], and to provide a Brønsted relation based upon six carboxylic acids with the exponent α = 0.42. These data indicate that the reaction proceeds via rate-determining proton transfer from the catalyzing acid to an olefinic carbon atom of the substrate. They also show tetramethoxyethene to be 1.0 × 106 times less reactive than 1,1-dimethoxyethene (ketene dimethyl acetal), a rate retardation 600 times greater than that expected from initial state stabilization by the two additional methoxy groups in tetramethoxyethene; possible causes of this disparity are discussed. Keywords: tetramethoxyethene, carbon–carbon double bond reactivity, ketene acetal, vinyl ether hydrolysis.

Intramolecular electrostatic catalysis in the hydrolysis of a bicyclic vinyl ether

Intramolecular electrostatic catalysis by a carboxylate ion has been observed in the hydrolysis of 2-methoxybicyclo[2.2.2]oct-2-ene-1-carboxylic acid in aqueous buffer solutions.

Concerning the weakness of intramolecular general acid catalysis in the hydrolysis of vinyl ethers. o‐carboxy‐α‐methoxy‐β,β‐dimethylstyrene

AbstractThe rate of hydrolysis of the aromatic vinyl ether o‐carboxy‐α‐methoxy‐β,β‐dimethylstyrene was found to be accelerated 25‐fold by ionization of its carboxylic acid group, but the effective molarity which may be calculated if all of this rate acceleration is ascribed to intramolecular general acid catalysis is only EM = 1 · 1 m. This is similar to the small effective molarities found before for intramolecular catalysis by carboxylic acid groups of aliphatic vinyl ethers, which shows that, unlike the situation in other intramolecular reactions, e.g. ketone enolization, the extra rigidity of aromatic over aliphatic systems does not improve the efficiency of intramolecular catalysis in vinyl ether hydrolysis.It is suggested that this behaviour is the result of reduced conjugation between the vinyl ether group and the aromatic ring in the transition state of the vinyl ether hydrolysis reaction, which retards the rate and offsets any improvement effected by increased rigidity of the aromatic system.

Vinyl ether hydrolysis. XVIII. The two-stage reaction of 2,3-dimethoxy-1,3-butadiene

The kinetics of acid-catalyzed hydrolysis of 2,3-dimethoxy-1,3-butadiene (1) to 3-methoxy-3-buten-2-one (2) and the subsequent 104 times slower conversion of the latter to biacetyl (3):[Formula: see text]were studied in aqueous solution at 25 °C. Both stages of this process give substantial hydrogen ion isotope effects, [Formula: see text] for Stage I and [Formula: see text] for Stage II, and Stage I shows general acid catalysis in formic and acetic acid buffers; both stages are therefore assigned the conventional mechanism for vinyl ether hydrolysis involving rate-determining proton transfer from catalyzing acid to substrate. The second vinyl ether group of the initial substrate (1) is found to have only a slight (3-fold) accelerative effect on the reactivity of the first group, but the acetyl substituent present in the intermediate 2 decreases its reactivity by a factor of 104; the latter appears to be due largely to the electron-withdrawing inductive effect of acetyl, with little or no influence from a countervailing electron-supplying resonance effect.

Reexamination of the alleged vinyl ether hydrolysis reaction of 9-methoxy-1-oxacyclonon-2-ene. Disproof of reversible carbon protonation

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTReexamination of the alleged vinyl ether hydrolysis reaction of 9-methoxy-1-oxacyclonon-2-ene. Disproof of reversible carbon protonationR. A. Burt, Y. Chiang, W. K. Chwang, A. J. Kresge, T. Okuyama, Y. S. Tang, and Y. YinCite this: J. Am. Chem. Soc. 1987, 109, 12, 3787–3788Publication Date (Print):June 1, 1987Publication History Published online1 May 2002Published inissue 1 June 1987https://doi.org/10.1021/ja00246a050RIGHTS & PERMISSIONSArticle Views88Altmetric-Citations7LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (297 KB) Get e-Alerts Get e-Alerts

Hydrolysis of acetaldehyde diethyl acetal and ethyl vinyl ether: secondary kinetic isotope effects in water and aqueous dioxane and the stability of the ethoxyethyl cation

Secondary deuterium isotope effects on the hydronium ion catalyzed hydrolysis of acetaldehyde diethyl acetal and ethyl vinyl ether were determined in wholly aqueous and aqueous dioxane solutions by comparing rates of reaction of the normal substrates with those of CD/sub 3/CH(OC/sub 2/H/sub 5/) and CH/sub 3/CD(OC/sub 2/H/sub 5/) and of CD/sub 2/=CHOC/sub 2/H/sub 5/ and CH/sub 2/=CDOC/sub 2/H/sub 5/. All of the isotope effects observed are consistent with the values expected on the basis of the changes in hyperconjugation, bond hybridization, and inductive effect which occur during the course of these reactions. The solvent dependence of the isotope effects, however, suggests that the ethoxyethyl cation intermediate generated in these reactions becomes sufficiently unstable in aqueous dioxane to require the conventional mechanisms for these reactions to give way to concerted pathways. 23 references, 2 tables.

Pseudo‐phase ion‐exchange model for micellar catalysis in the acid hydrolysis of vinyl ethers

AbstractThe rate of the perchloric acid hydrolysis of aqueous ethyl and butyl vinyl ethers at 25.0°C, in the presence of micellar aggregates [anionic, sodium dodecyl sulfate (SDS); cationic, cetyl trymethyl ammonium bromide (CTAB); and nonionic, polyoxyethylen23dodecanol, (Brij 35)], has been studied. Negligible effects were observed in the cases of cationic and nonionic micelles. Anionic micelles produce an enhancement in the reaction velocity, and the rate constants go through maxima with increasing SDS concentration. These maxima disappear in the presence of excess sodium perchlorate. All these facts are interpreted quantitatively by means of the pseudo‐phase ion‐exchange model.

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

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.

ChemInform Abstract: VINYL ETHER HYDROLYSIS. 16. 2‐CYCLOHEXYLIDENE‐3,3‐DIMETHYLOXETANE

Chemischer InformationsdienstVolume 14, Issue 52 Preparative Organic Chemistry ChemInform Abstract: VINYL ETHER HYDROLYSIS. 16. 2-CYCLOHEXYLIDENE-3,3-DIMETHYLOXETANE Y. CHIANG, Y. CHIANGSearch for more papers by this authorA. J. KRESGE, A. J. KRESGESearch for more papers by this authorW. F. WHITE, W. F. WHITESearch for more papers by this authorH. MARSCHALL, H. MARSCHALLSearch for more papers by this author Y. CHIANG, Y. CHIANGSearch for more papers by this authorA. J. KRESGE, A. J. KRESGESearch for more papers by this authorW. F. WHITE, W. F. WHITESearch for more papers by this authorH. MARSCHALL, H. MARSCHALLSearch for more papers by this author First published: December 27, 1983 https://doi.org/10.1002/chin.198352073Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume14, Issue52December 27, 1983 RelatedInformation

Vinyl ether hydrolysis. XIV. 2-Methoxy-2,3-dihydropyran: concurrent reaction of vinyl ether and acetal functional groups

The hydrolysis of 2-methoxy-2,3-dihydropyran shows a normal isotope effect (kH/kD > 1) under catalysis by the hydrogen ion and gives an accurately linear dependence of reaction rate upon undissociated acid concentration in cyanoacetic acid and formic acid buffer solutions. This substrate, therefore, unlike its higher homolog, 9-methoxyoxacyclonon-2-ene, provides no evidence in support of an anything but a normal mechanism for vinyl ether hydrolysis. Analysis of the hydrogen isotope effect suggests that a minor amount (8%) of this hydrolysis occurs via reaction of the acetal functional group.

Vinyl ether hydrolysis. XV. Methyl β,β-di-tert-butylvinyl ether: buttressing steric effects

The highly congested molecule, methyl β,β-di-tert-butyl vinyl ether, undergoes reaction in dilute aqueous mineral acid solutions by a normal vinyl ether hydrolysis mechanism and gives an unrearranged aldehyde product. The tert-butyl groups retard the rate of hydrolysis, but the effect of cis and trans substituents is not cumulative; this is attributed to a repulsive nonbonded interaction, relieved in the course of reaction, between the ether oxygen atom and the cis-tert-butyl group buttressed by the trans-tert-butyl group.

Mechanistic change in acid-catalyzed hydrolysis of silyl vinyl ethers

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMechanistic change in acid-catalyzed hydrolysis of silyl vinyl ethersMarilyn H. Novice, Hani R. Seikaly, Annette D. Seiz, and Thomas T. TidwellCite this: J. Am. Chem. Soc. 1980, 102, 18, 5835–5838Publication Date (Print):August 1, 1980Publication History Published online1 May 2002Published inissue 1 August 1980https://doi.org/10.1021/ja00538a023RIGHTS & PERMISSIONSArticle Views482Altmetric-Citations19LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (479 KB) Get e-Alerts Get e-Alerts

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

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.

Chemical stability of prostacyclin (PGI 2) in aqueous solutions

The rate constant for the hydrolysis of prostacyclin (PGI 2) to 6-keto-PGF 1α was measured by monitoring the UV spectral change, over a pH range 6 to 10 at 25°C and the total ionic strength of 0.5 M. The first-order rate constant (k∘ obs) extrapolated to zero buffer concentration follows an expression, k∘ obs = k H+ (H+), where k H+ is a second-order rate constant for the specific acid catalyzed hydrolysis. The value of k H+ obtained (3.71 × 10 4 sec −1 M −1) is estimated approximately 700-fold greater than a k H+ value expected from the hydrolysis of other vinyl ethers. Such an unusually high reactivity of PGI 2 even for a vinyl ether is attributed to a possible ring strain release that would occur upon the rate controlling protonation of C 5. A Brønsted slope (α) of 0.71 was obtained for the acid (including H 3O+) catalytic constants, from which a pH independent first-order rate constant for the spontaneous hydrolysis (catalyzed by H 2O as a general acid) was estimated to be 1.3 × 10 −6 sec −1. An apparent activation energy (E a) of 11.85 Kcal/mole was obtained for the hydrolysis at pH 7.48, from which a half-life of PGI 2 at 4°C was estimated to be approximately 14.5 min. when the total phosphate concentration is 0.165 M (cf. 3.5 min. at 25°C).

Vinyl ether hydrolysis. XI. The effect of α-phenyl substitution

The unexpected inability of an α-phenyl group to accelerate the rate of vinyl ether hydrolysis more strongly than an α-methyl substituent, k(CH2=CPhOEt)/k(CH2=CMeOEt) = 0.2 for catalysis by H3O+ at 25 °C, is examined and is found to be the result of two effects: (i) preferential initial state stabilization by phenyl and (ii) weak resonance interaction with the developing alkoxy carbonium ion in the transition state induced by the reactant-like character of the latter. A curved Brønsted relation for the hydrolysis of 3-methoxyindene catalyzed by carboxylic acids and monohydrogen phosphonate anions gives the Marcus theory parameters ΔG0≠ = 3 ± 1 kcal/mol and wr = 12 ± 1 kcal/mol.