Kinetics of the chromic acid oxidation of alcohols in aqueous acetone solutions

Lee, Donald G.; Downey, William L.; Maass, R. Michael

doi:10.1139/v68-070

Cited by 15 publications

(4 citation statements)

References 5 publications

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“…Correlation analysis using Hammett's relations between reaction rates and substituent parameters afforded values of the reaction constant for the oxidation of a set of secondary ( 5 ) and primary ( 21 ) benzyl alcohols with CsSO 4 F. The Hammett correlation plot for the transformation of 1-phenylethanols ( 5a-g ) to acetophenones, presented in Scheme , showed a satisfactory correlation of relative rate factors with σ + substituent constants and gave a straight line with slope ρ + = −0.32 and a correlation coefficient of 0.97, while the analysis of analogous data for a set of benzyl alcohols ( 21a-f , Scheme ) gave the value of −0.54 for the reaction constant and a correlation coefficient of 0.99. The reaction constant ρ + for the oxidation of 5 to 10 has the same sign but lower magnitude than those reported for the same reaction using dimethyldioxirane (ρ = −1.57), chromic acid (ρ = −1.16), or chromium trioxide in acetic acid solvent (ρ = −1.01) as oxidants and comparable to those for oxidation by chromium trioxide under basic (ρ = −0.52) or neutral (ρ = −0.37) conditions 13 or by S 2 O 8 2- −Cu II ( ρ = −0.27) . On the other hand, ρ + for the CsSO 4 F-mediated conversion of 21 to 22 is considerably lower than those for the oxidation of benzyl alcohols to benzaldehydes by HNO 3 (ρ = −2.25) or HNO 2 (ρ = −1.70, Yukawa−Tsuno method) and comparable to those found for conversion of benzaldehydes to benzoyl fluorides (ρ + = −0.38) 9 by CsSO 4 F.…”

Section: Resultsmentioning

confidence: 49%

Reactions of Alcohols with Cesium Fluoroxysulfate

1997

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The reactions of alcohols with cesium fluoroxysulfate (CsSO4F) in MeCN suspension were studied, and the role of the structure of the alcohol and the reaction conditions on the course of reaction was determined. Secondary benzyl alcohols bearing a nonactivating aromatic ring were selectively oxidized to the corresponding ketones, while the CsSO4F-mediated reaction of phenyl-1-naphthylmethanol resulted in the formation of 1-fluoronaphthalene and benzaldehyde. Cyclic and noncyclic secondary alcohols were readily converted to ketones, as well as 1-hydroxybenzocyclanes to benzocyclanones-1, without any further fluorination or oxidation under the reaction conditions. On the other hand, reactions of primary alcohols with CsSO4F resulted in the formation of acid fluorides derived from further fluorination of aldehydes. Another type of transformation was observed in the case of alcohols bearing a benzyl functional group attached geminal to a hydroxy group, where decarbonylation of reactive intermediates resulting in the formation of benzyl fluoride derivatives became the main process. 2-Phenylethanol was so converted to benzyl fluoride and phenylacetyl fluoride in a 3:1 relative ratio, while 2-phenyl-1-propanol was selectively transformed to 1-phenyl-1-fluoroethane. The presence of the radical inhibitor nitrobenzene in the reaction mixture considerably inhibited conversion of the starting material. The same effect was observed by lowering the solvent polarity. Hammett correlation analysis of the effect of substituents on the reaction rates of oxidation of a set of substituted 1-phenyl-1-ethanols to acetophenones gave the reaction constant ρ+ = −0.32, while analysis of analogous data for the transformations of benzyl alcohols to benzoyl fluorides gave the value of −0.54. A mechanism including radical intermediates was proposed for the transformation of alcohols by CsSO4F.

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Section: Resultsmentioning

confidence: 49%

Reactions of Alcohols with Cesium Fluoroxysulfate

1997

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“…The improved homogeneity in the reaction zone may be explained by stabilization of chromium esters with betulin, formed according to a Westheimer mechanism [27] which is due to aluminium cations (Scheme 1). …”

Section: Resultsmentioning

confidence: 99%

“…The decrease of the absorption at λ max = 360 nm means the concentration of Cr 6+ is decreasing and may be explained by the interaction of betulin ( 1 ) with Cr 6+ – H 2 SO 4 – oxidant resulting in formation chromate ester according to the Westheimer mechanism for the oxidation of alcohols [27]. The Westheimer mechanism involves the rapid initial formation of a chromate ester followed by the low rate determining, decomposition of the ester by removal of the α-proton by base B.…”

Section: Resultsmentioning

confidence: 99%

“…In aqueous acetone the base was considered to be water. Some reports consider chromium oxidation in acid medium as a process of conversion to the protonated bimetallic chromium (VI) species, resultant in the formation of the monochromate ester which, under the decomposition in the rate-determining step, to give the product [25,27]. Monitoring the absorption at 360 nm in time A = f (τ) in the initial reaction mixtures was studied.…”

Section: Resultsmentioning

confidence: 99%

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A Practical Synthesis of Betulonic Acid Using Selective Oxidation of Betulin on Aluminium Solid Support

et al. 2012

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The room temperature oxidation of betulin by Cr(VI) compounds in aqueous acetone on solid supports such as alumina, zeolites and silica gel has been studied. The oxidation on alumina support leaded to a single product—betulonic acid—in quantitative yield. One hundred percent selective oxidation during 30 min of betulin up to betulonic aldehyde was determined when silica gel support was used. The oxidation of betulin using zeolites as a support gives a mixture of betulonic acid and aldehyde in a 2:1 ratio. It is proposed the selective oxidation up to betulonic acid is due to the influence of Al3+-ions.

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Chemoselective addition of organotitanium reagents to carbonyl compounds

et al. 1985

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The conversion of classical carbanions such as RMgX, RLi, or deprotonated nitriles, sulfones, and carboxylic esters into titanium analogs results in reagents which add chemoselectively to carbonyl compounds in the presence of other functional groups. The standard titanating agent is chlorotriisopropoxytitanium (1). Grignard-type reactions and aldol additions are aldehydeselective in the presence of ketones. Other functional groups such as alkyl and aryl halides, esters, amides as well as nitro and cyano moieties are tolerated. Discrimination between two aldehydes or two ketones is also possible. Replacing alkoxy ligands by methyl groups at titanium increases reactivity dramatically, relative rates increasing in the series CH,Ti(OCHMe2), < (CH,),Ti-(OCHMe2), < (CH3),Ti. The latter reagent and its zirconium analog methylate sterically hindered and/or enolizable ketones which normally fail to undergo Grignard reactions. The ate complex H,C = CHCH,Ti(OCHMe$,MgCI (63) is aldehyde-selective, while the amino analog H,C = CHCH2Ti(NMe2)4MgC1 (64) adds selectively to ketones in the presence of aldehydes.Chemoselektive Addition von Organotitan-Agenzien an Carbonyl-Verbindungen Die Uberfuhrung von klassischen Carbanionen wie RMgX, RLi oder deprotonierten Nitrilen, Sulfonen oder Carbonsaureestern in Titan-Analoga ergibt Agenzien, die in Gegenwart von anderen funktionellen Gruppen chemoselektiv an Carbonylverbindungen addieren. Das StandardTitanierungsagens ist Chlortriisopropoxytitan (1). Grignard-artige Reaktionen sowie Aldoladditionen sind aldehyd-selektiv in Gegenwart von Ketonen. Andere funktionelle Gruppen wie Alkylund Arylhalogenide, Ester, Amide sowie Nitro-und Cyanreste werden toleriert. Die Unterscheidung zwischen zwei Aldehyden oder zwei Ketonen ist ebenfalls moglich. Der Ersatz von Alkoxyliganden durch Methylgruppen hat eine drastische Erhdhung der Reaktivitat zur Folge, d. h. die relativen Geschwindigkeiten nehmen in folgender Serie zu: CH,Ti(OCHMe,), < (CH3),Ti-(OCHMe2), < (CH,),Ti. Das letztere Agens sowie das Zirkon-Analogon methylieren sterisch gehinderte und/oder enolisierbare Ketone, die normalerweise keine Grignard-Reak tionen eingehen. Der At-Komplex H2C = CHCH2Ti(OCHMez),MgC1 (63) ist aldehyd-selektiv, wahrend die entsprechende Aminoverbindung H,C = CHCH2Ti(NMe2),MgC1 (64) selektiv mit Ketonen in Gegenwart von Aldehyden reagiert.Although carbanions play an important role in synthetic organic chemistry, lack of chemo-and stereoselectivity is frequently observed'). For example, phenylmagnesium bromide hardly discriminates between aldehydes and ketones2). Similar lack of chemoselectivity has been observed for other Grignard reagents and their lithium counterparts3) as well as for such resonance stabilized species as lithium ester enolates4), 0 VCH Verlagsgesellschaft mbH, D-6940 Weinheim, 1985

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Kinetics of the chromic acid oxidation of alcohols in aqueous acetone solutions

Cited by 15 publications

References 5 publications

Reactions of Alcohols with Cesium Fluoroxysulfate

Reactions of Alcohols with Cesium Fluoroxysulfate

A Practical Synthesis of Betulonic Acid Using Selective Oxidation of Betulin on Aluminium Solid Support

Chemoselective addition of organotitanium reagents to carbonyl compounds

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