The Aldol Condensation of Acetaldehyde: the Equilibrium Constant for the Reaction and the Rate Constant for the Hydroxide Catalyzed RetroAldol Reaction

Guthrie, J. Peter

doi:10.1139/v74-294

Cited by 37 publications

(25 citation statements)

References 7 publications

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“…2. We had previously (2) found that for crotonaldehyde, 2 b , k,, , kz3, and l / K l showed a dependence upon hydroxide concentration of the form: Similar behavior appears to be shown here, although one cannot be very confident because the variation with changing hydroxide concentration is only clearly greater than experimental error for k z I . Table 2 shows the second order rate constants for the individual steps evaluated in this work, corrected where appropriate to zero hydroxide ion concentration.…”

supporting

confidence: 84%

“…Thus one can see no sign of the two stages which are believed to be essential for this reaction (eqs. [I] and [2])…”

Section: Resultsmentioning

confidence: 99%

“…This is in large measure due to the great potential for complexity for most aldol reactions, with various modes of reaction, competing equilibria, and polymerization leading to hopelessly complicated mixtures. We have shown that much of this complexity can be avoided by studying the retroaldol reaction at low concentrations, in a study of the reaction of crotonaldehyde in dilute aqueous base (2). We now wish to report a study of a closely related compound with one additional carbon methyl group, namely 3-methyl-2-butenal, l c .…”

Section: Introductionmentioning

confidence: 99%

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The retroaldol reaction of 3-methyl-2-butenal

Guthrie¹,

Dawson²

1983

Can. J. Chem.

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Can. J. Chem. 61, 171 (1983). In aqueous sodium hydroxide solutions at 25OC, 3-methyl-2-butenal, I c , undergoes retroaldol cleavage to acetone and acetaldehyde. The kinetics of thc rctroaldol reaction wcrc followed spectrophotometrically at 242 nm and showed simple first order behavior. When 3-methyl-3-hydroxybutanal, 2c, was added to aqueous sodium hydroxide solutions at X°C, there was an initial increase in absorbance at 242 nm, attributed to formation of l c , followed by a 20-fold slower dccrcase; the rate of the slow decrease matches the rate of disappearance of l c under the same conditions. Analysis of the kinetics allows determination of the three rate constants needed to describe the system: kl,,, = 0.00342; kdchy,, = 0.00832; k,,,, = 0.0564; all M-' s-I. The equilibrium constant for enone hydration is 0.41. Rate constants for the analogous reactions for acrolein and crotonaldehyde could be obtained from the literature. There is a reasonable rate-equilibrium correlation for the retroaldol step. For the enone hydration step, rate and equilibrium constants respond differently to replacement of hydrogen by methyl. It is proposed that this results from release of strain after the rate-determining step by rotation about a single bond; this decrease in strain is reflected in the equilibrium constant but not in the rate constant.J. PETER GUTHRIE et BRIAN A. DAWSON. Can. J. Chem. 61, 171 (1983). Le methyl-3 buttnal-2 ( l c ) , dans des solutions aqueuses d'hydroxyde de sodium a 25"C, subit un clivage rCtroaldolique conduisant a I'acttone et I'acCtaldChyde. On a suivi spectrophomCtriquement a 242 nm la cinCtique de cette rtaction simple d'ordre un. Lorsqu'on ajoute du mCthyl-3 hydroxy-3 butanal (2c) des solutions aqucuses d'hydroxyde de sodium 5 25"C, il y a une augmentation initiale de I'absorption 2 242 nm que I'on attribue la formation du compost I c suivie d'une diminution qui est 20 fois plus lente; le taux de la faible diminution correspond au taux de disparition du produit l c dans ces rn&mes conditions. L'analyse des donnCes cinttiques permet de dtterminer les trois constantes de vitesse necessaires a la description Introduction We have reported a study (1) of the equilibrium constants for aldol condensation reactions. It seemed highly desirable to look for rate-equilibrium correlations for these synthetically important reactions, particularly since equilibrium constants were now available. However, there have been comparatively few kinetics investigations of aldol reactions. This is in large measure due to the great potential for complexity for most aldol reactions, with various modes of reaction, competing equilibria, and polymerization leading to hopelessly complicated mixtures. We have shown that much of this complexity can be avoided by studying the retroaldol reaction at low concentrations, in a study of the reaction of crotonaldehyde in dilute aqueous base (2). We now wish to report a study of a closely related compound with one additional carbon methyl group, namely 3-methyl-2-butenal, l c . Th...

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supporting

confidence: 84%

“…Thus one can see no sign of the two stages which are believed to be essential for this reaction (eqs. [I] and [2])…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The retroaldol reaction of 3-methyl-2-butenal

Guthrie¹,

Dawson²

1983

Can. J. Chem.

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“…This reaction turned out to be somewhat more difficult to sort out, but we have now completed the kinetic analysis, and wish to report it in turn. This provides another example of a fully analyzed aldol condensation, to add to those we (1,(4)(5)(6)(7)(8)(9)(10) and others (1 1-14) have previously reported. To complete the analysis we had to develop computer programs allowing us to fit simultaneously multiple sets of data described by equations with common parameters.…”

Section: Introductionsupporting

confidence: 64%

The aldol condensation of acetone with acetophenone

Guthrie¹,

Wang²

1992

Can. J. Chem.

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). The kinetics and equilibria involved in the aldol condensation of acetone, acting as carbon acid, and acetophenone have been studied in aqueous alkaline solution. The enone isolated is the E isomer. The reactions are all first order in hydroxide, with rate and equilibrium constants (defined for E-enone as initial compound) of: k12 = (5. There is an equilibration of the two enones in base that is faster than hydration to the ketol: k14 = (3.14 f 0.8455To analyze the behavior of the enone:ketol equililbrium system in acid we simultaneously fitted analytical data for all three species (E-enone, Z-enone, and ketol) to a kinetic model, so that the rate constants were determined by the best fit to all of the data for an experiment. J . PETER GUTHRIE et XIAO-PING W A N G .Can [Traduit par la rkdaction]

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“…In the C2 pathway, the C−C bond remains intact and ethanol can be oxidized to acetaldehyde and acetic acid. In an alkaline medium, acetate is stable and acetaldehyde undergoes polymerization [10,11]. This can be compared with the C1 pathway, in which C−C bond cleavage takes place, producing adsorbed CO and adsorbed CH x , which subsequently oxidize to CO 2 which remains in solution as carbonate in alkaline media.…”

Section: Introductionmentioning

confidence: 99%

Potential oscillations during electro-oxidation of ethanol on platinum in alkaline media: The role of surface sites

Sallum

González²,

Feliu

2016

Electrochemistry Communications

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Potential oscillations during electro-oxidation of ethanol on platinum in alkaline media: The role of surface sites, Electrochemistry Communications (2016Communications ( ), doi: 10.1016Communications ( /j.elecom.2016 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT AbstractThe electro-oxidation of small organic molecules is one of the major areas of interest in electrocatalysis due to its potential use in energy conversion. Instabilities in alkaline solution, particularly in comparison with kinetic properties in a conventional regime, are rarely reported in the literature, despite the fact that the catalytic activity is higher in this medium and the onset potential is shifted to lower values compared to acidic media.Ethanol oxidation on polycrystalline platinum exhibits oscillations under galvanostatic control. As the reaction is structure-sensitive, it is possible to study the contribution of the three platinum basal planes to the complex kinetics. We found that Pt(100) has the major influence in the overall non-linear kinetics of ethanol electro-oxidation on Pt(poly), possibly because it has the highest formation and accumulation rate of CO ads . Based on the differences observed in the galvanostatic transients on Pt(poly), Pt(110) and Pt(100), and the absence of this behaviour on Pt(111), it is possible to infer that surface sites strongly influence the kinetic scenario during the ethanol oxidation reaction.

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The Aldol Condensation of Acetaldehyde: the Equilibrium Constant for the Reaction and the Rate Constant for the Hydroxide Catalyzed RetroAldol Reaction

Cited by 37 publications

References 7 publications

The retroaldol reaction of 3-methyl-2-butenal

The retroaldol reaction of 3-methyl-2-butenal

The aldol condensation of acetone with acetophenone

Potential oscillations during electro-oxidation of ethanol on platinum in alkaline media: The role of surface sites

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