Acetone Enolate Research Articles

ChemInform Abstract: LOW TEMPERATURE PHOTOCHEMISTRY OF THE ACETONE/2‐PROPANOL SYSTEM

AbstractNach 10stündiger Tieftemperatur‐Photolyse eines äquimolaren Aceton (I)/Isopropanol (II)‐Gemisches wurden aus dem Reaktionsprodukt die Verbindungen (III) bis (VII) im Verhältnis 1:0,5:0,2:0,2:0,1 isoliert.

Bifunctional catalysis of the enolization of acetone

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTBifunctional catalysis of the enolization of acetoneA. F. Hegarty and W. P. JencksCite this: J. Am. Chem. Soc. 1975, 97, 24, 7188–7189Publication Date (Print):November 1, 1975Publication History Published online1 May 2002Published inissue 1 November 1975https://doi.org/10.1021/ja00857a052RIGHTS & PERMISSIONSArticle Views149Altmetric-Citations36LEARN 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 (302 KB) Get e-Alerts Get e-Alerts

Low Temperature Photochemistry of the Acetone/2‐Propanol System

AbstractDuring UV.‐irradiation of acetone/2‐propanol mixtures at −70° products of photo‐addition of acetone to intermediate enols are formed. The yields of these products exceed the yield of pinacol, the major room temperature product. At −70° the photoadditions are favoured by the long lifetime of acetone enol (≥ 5000 s).

On the synthesis of arylacetones by the Srn 1 arylation of acetone enolate ion.

Numerous aryl bromides and iodides react with acetone enolate ion in liquid ammonia under irradiation to form arylacetones in high yield. This synthesis is successful with bromo-or iodobenzene derivatives carrying alkoxy, alkyl, phenyl, halogen, and carboxylate substituents, and with halogen derivatives of polynuclear aromatic hydrocarbons. The method is remarkably insensitive to steric hindrance ; for example, 2, 4, 6-triethylbromobenzene reacts quite well. With greater steric hindrance, as in 2, 4, 6-triisopropyliodobenzene, reactivity falls and a side reaction of dehalogenation becomes appreciable, for reasons which are suggested. The synthesis was unsuccessful with the diethylamino, nitro and ionized hydroxy (-O-) substituents. Potassium metal-stimulated reactions of a few aryl diethyl phosphates with acetone enolate ion give generally lower yields of arylation and larger yields of dephosphation (hydrocarbon) products, compared even to potassium-stimulated reactions with aryl bromides. It is postulated that the lesser formation of hydrocarbon products from the aryl bromides is related to transport effects and solution inhomogeneity.

Acidity of Hydrated Sulfates Revealed by the Enolization of Acetone

Acidity of Hydrated Sulfates Revealed by the Enolization of Acetone

Kinetics of Bromination of Acetone, Bromoacetone, and 1,1-Dibromoacetone

The rate of bromine consumption in acetate-promoted bromination of acetone is not measurably dependent on bromine concentration, in confirmation of earlier work. This result casts doubt on the existence of recently-reported, nonenolic mechanisms for bromination of butanone under similar conditions. The effects of alpha bromine substituents on rates of enolization of acetone are reported.

Kinetic analysis of the bromination of acetone in an acidic medium: solvent isotope effect on the rate of enol ketonization

The solvent isotope effect on the ketonization of acetone enol demonstrates the similarity of this reaction and the hydrolysis of enol ethers.

Keto-enol tautomerization: A thermodynamic and kinetic study

Measuring the extent of enolization of acetoacetic ester and acetyl acetone at various temperatures enables the thermodynamics of these two systems to be studied and compared.

Solvent isotope effects in the enolization of acetaldehyde, acetone, and ethyl methyl ketone at high acidities

Measurements of enolization rates in D2O-D2SO4 mixtures and H2O-H2SO4 mixtures at high acidities yield data which support low (c. -7) values for the pKa values of the protonated forms of acetaldehyde, acetone, and ethyl methyl ketone.

Ketimine Intermediates in Amine-Catalyzed Enolization of Acetone1a

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTKetimine Intermediates in Amine-Catalyzed Enolization of Acetone1aMyron L. Bender and Andrew WilliamsCite this: J. Am. Chem. Soc. 1966, 88, 11, 2502–2508Publication Date (Print):June 1, 1966Publication History Published online1 May 2002Published inissue 1 June 1966https://doi.org/10.1021/ja00963a026RIGHTS & PERMISSIONSArticle Views239Altmetric-Citations42LEARN 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 (806 KB) Get e-Alerts Get e-Alerts

EFFECT OF PRESSURE ON THE ACID-CATALYZED ENOLIZATION OF ACETONE AND ACETOPHENONE IN VARIOUS ETHANOL–WATER SOLVENTS. ORIGIN OF THE ENTHALPY–ENTROPY COMPENSATION EFFECT

The effect of pressure, temperature, and solvent composition on the rate of the acid-catalyzed enolization of acetone and acetophenone, and the solvent deuterium isotope effect for the enolization of acetophenone, have been measured by following the iodination. The solvent deuterium isotope effect [Formula: see text] for the enolization of acetophenone in 16.2% w/w ethanol–water is 2.50 ± ~0.05, which undoubtedly proves that there is a pre-equilibrium proton transfer. The effect of solvent in the range water to 33.4% w/w ethanol in water on the rate of enolization of both acetone and acetophenone is small at atmospheric pressure, but is about four times larger at 3 kbar. This cannot be explained on simple electrostatic grounds, and indicates that any simple electrostatic explanation of the solvent effect at atmospheric pressure is invalid. The volumes of activation for the enolizations are strongly dependent on the solvent, that for acetone varying from −2.l ± ~0.5 to −6.9 ± ~ 0.7 cm3 mole−1 between solvents water and 33.4% w/w ethanol in water.An examination has been made of the enthalpyentropy compensation effect. It is shown that in general if the rate or equilibrium constant of a reaction does not change with changing conditions (such as solvent, substituents, etc.) then either the quantities of activation at constant pressure, ΔHp≠ and ΔSp≠, or the corresponding quantities at constant volume, ΔUv≠ and ΔSv≠, must vary in a compensating manner, and the existence of an energy–entropy compensation effect is inevitable. For the enolization of acetone and acetophenone in ethanol–water mixtures, ΔUv≠ and ΔSv≠ vary only slightly with solvent, whereas ΔHp≠ and ΔSp≠ vary in a compensating manner. The main causes of the compensation effect in the constant-pressure parameters are, in a sense, the change with changing solvent of the thermal expansion of the solvent and of the volume of activation of the reaction. On the other hand, both the constant-pressure and the constant-volume parameters vary with substituent from acetone to acetophenone, and the constant-volume parameters vary the more.

The acetone complex of nitroprusside ion

The nitroprusside ion, which may be regarded as a special carrier of the nitrosonium ion, forms a 1:1 complex with acetone, the rate of formation of the complex being the same as the rate of enolization of acetone. By considering the infra-red absorption spectrum of the analogous acetophenone complex some suggestions as to the structure of the acetone complex can be made. The latter decomposes in alkaline solution to aquopentacyanide ion and isonitrosoacetone, the rate of decomposition being proportional to the concentration of the complex. In 1–6 M NaOH the rate of decomposition depends on the first power of the hydroxyl ion concentration, and in 6–12 M NaOH the rate varies inversely as the cube of the hydroxyl ion concentration.

The Concerted Mechanism in Acid-Base Catalysis

THE velocity, ν 9 of reactions which exhibit general acid-base catalysis in carboxylate buffers is generally assumed to conform to the equation : where the various catalytic constants, k, are differentiated by their subscripts. However, Dawson and Spivey1 reported in 1930 that the quantitative description of the rate of enolization of acetone, as measured by its iodination in acetate buffers, required an additional cross-term k x[HA][A−]. The experimental result was substantiated in 1953 by Bell and Jones2, who also found similar cross-terms, which may account for up to 20 per cent of ν, for trimethylacetate and glycollate buffers. These data are widely considered to be the sole evidence3,4 for the occurrence in aqueous solution of a catalytic mechanism, which requires the simultaneous presence of an acid and a base in the transition state complex. The process has been variously described3,4 as ‘concerted’, ‘synchronous’, ‘push-pull’, ‘ternary’ (with reference to the hypothetical number of species in the transition state) and ‘bimolecular’ (with reference to the hypothetical number of catalytic molecules).

IONIZATION OF ORGANIC COMPOUNDS IN ACID I. ALIPHATIC KETONES

The changes in the ultraviolet absorption spectra of aliphatic ketones in aqueous sulphuric acid have been followed as the acid strength is increased from 0 to 98%. With increase in strength up to 65% the weak peak at about 270 mμ is shifted to shorter wavelengths by a medium effect. However, with further increase in acid strength the peak disappears altogether because of protonation of the carbonyl group. The pKBH+ values of several ketones have been calculated from the spectrophotometric results to be about −7. The pKBH+ values of cyclic ketones vary systematically with ring size. The significance of the present work to recent studies on the rate of enolization of acetone is discussed.

The Heat of Hydrolysis of i-Propenyl Acetate and m-Cresyl Acetate and the Heat of Enolization of Acetone.

The Heat of Hydrolysis of i-Propenyl Acetate and m-Cresyl Acetate and the Heat of Enolization of Acetone.

THE IODIMETRIC ESTIMATION OF ACETONE

The iodimetric estimation of acetone is directly related to two factors: (1) the enolization of acetone by alkali, and (2) the relative velocities of (1) and the reaction between alkali and iodine. The experiments necessary to emphasize these factors indicate the great rapidity of these two reactions at 25 °C.