The hydrolysis of coumarin diethyl acetal and the lactonization of coumarinic acid ethyl ester. The partitioning of tetrahedral intermediates generated from independent sources

1979 ◽  
Vol 57 (17) ◽  
pp. 2260-2267 ◽  
Author(s):  
R. A. McClelland ◽  
R. Somani ◽  
A. J. Kresge
Keyword(s):  
Ethyl Ester ◽  
Acid Ester ◽  
Acid Ethyl Ester ◽  
Major Product ◽  
Low Ph ◽  
Diethyl Acetal ◽  
Acidic Solutions ◽  
Rate Determining Step ◽  
Hydrolysis Of ◽  
Tetrahedral Intermediates

The hydrolysis of coumarin diethyl acetal to coumarin proceeds via two detectable intermediates. A short-lived transient is observed in strongly acidic solutions (pH < 2.5); this is the oxocarbonium ion intermediate of the hydrolysis. That this cation can be detected suggests unusual stability, a fact which can be explained in terms of its pyrilium ion nature. A long-lived intermediate is also observed; kinetic and spectral evidence suggest that this is coumarinic acid ethyl ester. The lactonization of this ester shows a change in rate-determining step as the pH is varied. A corresponding change in products is found in the acetal hydrolysis, the coumarinic acid ester being the major product at high pH, with coumarin the major product at low pH. Both observations can be explained in terms of different modes of partitioning of cationic and neutral tetrahedral intermediates. Analysis in quantitative terms shows that the same tetrahedral intermediate is generated in the two different cases.

scholarly journals The tert-butylaminomethyl(mesityl)phosphinic acid ester and formation of its zinc dichloride complex: syntheses and characterization

2018 ◽  
Vol 41 (3-4) ◽  
pp. 109-113
Author(s):  
Michael Lutter ◽  
Lukas M. Stratmann ◽  
Klaus Jurkschat
Keyword(s):  
Solid State ◽  
Ethyl Ester ◽  
Acid Ester ◽  
Phosphinic Acid ◽  
Acid Ethyl Ester

Abstract The syntheses and structures of tert-butylaminomethyl(mesityl)phosphinic acid ethyl ester 2 and its zinc dichloride complex 3 are reported. In the solid state, both compounds are dimeric via hydrogen bridges. In the complex 3, the phosphinic acid ester 2 coordinates the zinc dichloride diastereoselectively.

Synthesen von Heterocyclen, CC Reaktionen mit cyclischen Oxalylverbindungen, XVIII Zur Reaktion von 4-Benzoyl-5-phenyl-2,3-dihydrofuran-2,3-dion mit Η-aktiven Nucleophilen. / Syntheses of Heterocycles, CC Reactions of Cyclic Oxalyl Compounds, XVIII The Reaction of 4-Benzoyl-5-phenyl-2,3-dihydrofuran-2,3-dione with Η-active Nucleophiles

1976 ◽  
Vol 31 (11) ◽  
pp. 1511-1514 ◽  
Author(s):  
Gert Kollenz ◽  
Erich Ziegler ◽  
Walter Ott ◽  
Herwig Igel
Keyword(s):  
Acetic Acid ◽  
Acrylic Acid ◽  
Oxalic Acid ◽  
Ethyl Ester ◽  
Acid Ethyl Ester ◽  
The Other ◽  
Other Hand ◽  
Hydrolysis Of ◽  
Acid Anilides

Hydrolysis of 4-Benzoyl-5-phenyl-2,3-dihydrofuran-2,3-dione (1) in water (ethanol) gives dibenzoylmethane and oxalic acid (ethyl ester). 1 reacts with aniline or p-toluidine yielding the 2-pyrrolones (2), which on the other hand are synthesized by addition of the corresponding anilines to the pyrrol-2,3-diones (8). 3 a adds methanol to give the 2-pyrrolone (4), which with aniline can be converted into 2 a. 2 a, b show fragmentation to oxalic acid anilides by heating (2 b) or treating with diazomethane (2 a). The reaction of 1 with p-nitroaniline leads via the furanone-derivative 6 to oxalic acid-di-p-nitroanilide. 1 and N-methylaniline combine to acrylic acid-N-methylanilide (7), which by heating gives the dibenzoyl acetic acid-N-methylanilide

A change in rate-determining step in the hydrolysis of cyclic ketals

1984 ◽  
Vol 62 (8) ◽  
pp. 1608-1612
Author(s):  
Robert A. McClelland ◽  
N. Esther Seaman
Keyword(s):  
Bond Cleavage ◽  
Structural Features ◽  
Product Formation ◽  
Low Ph ◽  
Alkoxy Group ◽  
Hydroxide Ion ◽  
Rate Determining Step ◽  
The Difference ◽  
Ortho Esters ◽  
Hydrolysis Of

A kinetic study is reported of the hydrolysis of 2-methoxy-2-phenyltetrahydrofuran and 2-ethoxy-2-phenyltetrahydrofuran. At pH > 6 the rate-determining step involves H+-catalyzed formation of the oxocarbocation, this reaction occurring with cleavage of the exocyclic alkoxy group to produce a cyclic cation. Between pH 5 and pH 6 a change-over occurs and at pH < 5, the rate-determining step in product formation is breakdown of the cyclic hemiketal intermediate, 2-hydroxy-2-phenyltetrahydrofuran. The changeover occurs because the H+-catalyzed breakdown of this intermediate is a slower process than the H+-catalyzed oxocarbocation-forming step. Hydroxide ion catalysis makes the hemiketal decomposition faster at higher pH. Analogous cyclic ortho esters (2-alkoxy-1,3-dioxolanes) show this same change in rate-determining step between high pH and low pH, while acyclic acetals, ketals, and ortho esters generally have the oxocarbocation-forming stage rate determining at all acidities. It is concluded that the structural features inherent in the cyclic systems are responsible for the difference. In particular, the oxocarbocation-forming stage involves exocyclic bond cleavage, giving it an entropic advantage over the hemiketal or hemiorthoester breakdown which is endocyclic.

Hydrolysis of trioxaadamantane ortho esters. II. Kinetic analysis and the nature of the rate-determining step

1984 ◽  
Vol 62 (6) ◽  
pp. 1074-1080 ◽  
Author(s):  
Robert A. McClelland ◽  
Patrick W. K. Lam
Keyword(s):  
Rate Constants ◽  
Product Formation ◽  
Low Ph ◽  
Acid Solutions ◽  
Ortho Ester ◽  
Rate Determining Step ◽  
Acid Catalyzed ◽  
Cation Hydration ◽  
Ortho Esters ◽  
Hydrolysis Of

A detailed kinetic study of the hydrolysis of a series of 3-aryl-2,4,10-trioxaadamantanes is reported. These ortho esters equilibrate with the ring-opened dialkoxycarbocation, in a very rapid process which could be studied using temperature-jump spectroscopy for aryl = 2,4-dimethylphenyl. Relaxation rate constants are of the order of 104 s−1; these could be analyzed to provide the rate constants for both the ring opening and the ring closing. Product formation from this equilibrating mixture is much slower. In acid solutions (0.01 M H+ −50% H2SO4), first-order rate constants for product formation initially increase with increasing acidity, but a maximum is reached at 20–35% H2SO4 and the rate then falls. This behavior is explained by a counterbalancing of two factors. Increasing acidity increases the amount of the dialkoxycarbocation in the initial equilibrium, but, outside the pH region, it decreases the rate of hydrolysis of this cation through a medium effect. Rate constants over a range of pH have been measured for two trioxaadamantanes and for the cation DEt+ derived by treatment of the ortho ester with triethyloxonium tetraafluoroborate. The latter models the cation formed in the ortho ester hydrolysis but it cannot ring close. Rate–pH profiles obtained in these systems are more complex than expected on the basis of rate-determining cation hydration. An interpretation is proposed with a change in rate-determining step between high pH and low pH. Cation hydration is rate determining at high pH but at low pH hemiorthoester decomposition becomes rate determining. Under these conditions the hemiorthoester equilibrates with both the dialkoxycarbocation and with the trioxaadamantane. The change in rate-determining step occurs because acid-catalyzed reversion of the hemiorthoester to dialkoxycarbocation is a faster process than acid-catalyzed hemiorthoester decomposition. This makes the latter rate-determining in acid solutions. Additional pathways available to the decomposition, however, make it the faster process at higher pH. A kinetic analysis furnishes all of the rate and equilibrium constants for the system, and provides support for the mechanistic interpretation. A comparison of these numbers with those obtained for the three stages in the hydrolysis of a simple monocyclic ortho ester underlines the novelty of the trioxaadamantane system.

Wet Chemical Cleaning of InP and InGaAs

2012 ◽  
Vol 187 ◽  
pp. 27-31 ◽  
Author(s):  
Rita Vos ◽  
Sophia Arnauts ◽  
Thierry Conard ◽  
Alain Moussa ◽  
Herbert Struyf ◽  
...  
Keyword(s):  
Semiconductor Manufacturing ◽  
Low Ph ◽  
Native Oxide ◽  
Chemical Cleaning ◽  
Acidic Hydrolysis ◽  
Free Surfaces ◽  
Acidic Solutions ◽  
Wet Chemical ◽  
Hydrolysis Of

In this work, the compatibility of InP and InGaAs in cleaning solutions commonly used in semiconductor manufacturing is investigated. Aqueous oxidizing cleans should be avoided as the substrates dissolve rapidly. Low pH solutions may impose some serious ES&H issues due to hydride evolution occurring upon acidic hydrolysis of the III-V material. However, acidic solutions are very efficient to remove the native oxide from the substrate. Complete oxide free surfaces are not achieved after wet cleaning due to the rapid oxidation of these materials in the atmosphere.

Trypsin-catalyzed Hydrolysis of N-Benzoyl-L-arginine Ethyl Ester at Low pH*

Biochemistry ◽  
1965 ◽  
Vol 4 (6) ◽  
pp. 1086-1091 ◽  
Author(s):  
James A. Stewart ◽  
Jerry E. Dobson
Keyword(s):  
Ethyl Ester ◽  
Low Ph ◽  
Hydrolysis Of

Lipase-catalyzed hydrolysis of 2-(4-hydroxyphenyl)propionic acid ethyl ester to (R)-(−)-2-(4-hydroxyphenyl)propanoic acid

2019 ◽  
Vol 73 (10) ◽  
pp. 2461-2468 ◽  
Author(s):  
Xin Yuan ◽  
Panliang Zhang ◽  
Guangyong Liu ◽  
Weifeng Xu ◽  
Kewen Tang
Keyword(s):  
Ethyl Ester ◽  
Propionic Acid ◽  
Acid Ethyl Ester ◽  
Propanoic Acid ◽  
Hydrolysis Of
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