The Hydration of Unsaturated Compounds. XII. The Rate of Hydration of β,β-Dimethylacrolein and its Equilibrium with β-Hydroxyisovaleraldehyde<sup>1</sup>

Lucas, H. J.; Stewart, W. T.; Pressman, David

doi:10.1021/ja01239a004

Cited by 8 publications

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“…The possibility that it is an artefact caused by imperfect matching of salt effects between KC1 and NaOH must be kept in mind. The enone hydration2 of l c has been studied in acidic solution by Lucas et al (4). In experiments at 25°C and ionic strength 1.04, these authors report a hydration constant of 0.39, which is in reasonable accord with our value at ionic strength of 0.1 of 0.41.…”

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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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“…It is straightforward to derive eq. [4] a function of the basicity constant K,, the total base concentration B, and the formaldehyde concentration F.…”

Section: Comparison With Lower Homologsmentioning

confidence: 99%

The retroaldol reaction of 3-methyl-2-butenal

Guthrie¹,

Dawson²

1983

Can. J. Chem.

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Liberation of Staling Aldehydes During Storage of Beer

Barker¹,

Gracey²,

Irwin³

et al. 1983

Journal of the Institute of Brewing

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Trans-2-nonsnal, 3-hydroxynonanal and 3-hydroxybutanal were isolated from barley and wort and mass spectral evidence for the presence of further hydroxyaldehydes was found. The concentration of free aldehydes in a model solution was found to decrease in the presence of bisulphite. Addition of acetaldehyde to a mixture of aldehyde bisulphite complexes released trans-2-nonenal in preference to other aldehydes.The concentration of sulphite in beer decreased by 66% over four months. This data was combined in a theory in which the papery, cardboard stage of beer staling is ascribed to a decrease in bisulphite concentration and subsequent bisulphite transfer from unsaturated aldehyde bisulphite addition complexes.

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