The inherent instability of dimethylformamide–water systems containing hydroxide ion

Buncel, Erwin; Symons, E. A.

doi:10.1039/c29700000164

Cited by 41 publications

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“…Exchange We had previously observed (41,42) that DMF reacts readily with hydroxide ion, to give formate ion and dimethylamine, despite a statement in the literature suggesting the ~o n t i a r y .~…”

Section: Effect Of Basic Hydrolysis Of Dmf On Protonmentioning

confidence: 99%

“…The magnitude of such rate enhancement can, however, vary greatly depending on the system involved. Thus whereas a number of processes in which proton transfer from substrate to base is rate-determining exhibit rate enhancements of 101° or more when the medium is changed from aqueous (or alcoholic) to --99mol% DMSO (33)(34)(35)(36)(37)(38), exchange of D2 in the DMSO-H20-OHp system is accelerated only by -lo4 when the medium is changed from purely aqueous to 99.5% DMSO (39,40).…”

Section: Mediutn Dependence Of Proton Exchangementioning

confidence: 99%

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Hydrogen exchange studies. XIV. Kinetics and mechanism of base-catalyzed hydrogen exchange in 1,3-dinitrobenzene in aqueous dimethylformamide and relationship with σ-complex formation

Buncel¹,

Zabel²

1981

Can. J. Chem.

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ERWIN BUNCEL and ALLEN W. ZABEL. Can. J . Chem. 59, 3177 (1981). Kinetic data have been evaluated for hydrogen exchange in 1,3-dinitrobenzene (DNB), occurring at the 2-position, in dimethylformamide (DMF) -D,O mixtures containing deuteroxide ion. The pseudo first order rate constants for exchange, k,,,. show inverse dependence on the initial DNB concentration, which can be quantitatively related to the extent of o-complex formation in these systems. The profile fork,,,, as function of medium compositio~l exhibits a maximum at ca. 70 mol% DMF, and E ,~, for o-complex formation reaches a plateau at about the same medium composition. The equilibrium constants for o-complex formation, K,, are used to calculate the free. or uncomplexed, deuteroxide ion concentrations, which then allow one to calculate k 2 . the second order rate constants for exchange. The k, values show a uniformly increasing tendency with increased DMF content. Correlations with medium basicity are examined, and the nature of the log k, and log K, vs. H-plots afford insight into the origin of the medium dependence of proton exchange. The results of the present study are consistent with the cr-complex being an unreactive form of the substrate towards exchange, which occurs via uncomplexed DNB present in small concentration. The study also rules out the possibility that the colored species present in these systems is the carbanion formed on deprotonation of DNB.ERWIN BUNCEL et ALLEN W . ZABEL. Can. J. Chem. 59. 3177 (1981). O n a evalue les donnees cinetiques de l'echange d'hydrogene se produisant en position 2 du dinitro-1,3 benzene (DNB) dans des melanges de dimethylformamide (DMF) -D,O contenant I'ion deuteroxyde. L a constante de vitesse d e pseudo ordre un de l'echange k,,,, revele un effet inverse de la concentration initiale de DNB qui peut etre relie quantitativement aux taux deformation du complexe o dans ces systemes. 1.e profil de k,,, en fonction de la composition du milieu montre un maximum pour environ 70 molR de DMF et le E, , , de la formation du complexeo atteint un plateau pour environ la meme composition du milieu. On a utilise la constante d'equilibre d e la formation du complexe o K,, pour calculer les concentrations de I'ion deuteroxyde libre. ou non complexe qui permettent de calculer k, la constante d e vitesse d'ordre deux de I'echange. Les valeurs de k2 montrent une tendance d'augmentation uniforme avec la teneur en DMF. On a examine les correlations avec la basicite du milieu; la nature des courbes de log k, et log K, en fonction de H-fournit des renseignements sur I'origine de l'effet du milieu lors de I'echange de proton. Les resultats de la presente etude sont en accord avec un complexe o qui ne donnerait pas de reaction d'echange celui-ci se produisant par I'intermediaire du DNB non complexe present a une concentration faible. L'etude ecarte egalement la possibilite que l'espece coloree presente dans ces systemes soit le carbanion forme par la protonation du DNB.[Traduit par le journal]

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Section: Effect Of Basic Hydrolysis Of Dmf On Protonmentioning

confidence: 99%

Section: Mediutn Dependence Of Proton Exchangementioning

confidence: 99%

Hydrogen exchange studies. XIV. Kinetics and mechanism of base-catalyzed hydrogen exchange in 1,3-dinitrobenzene in aqueous dimethylformamide and relationship with σ-complex formation

Buncel¹,

Zabel²

1981

Can. J. Chem.

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“…A 29.2 111 aliquot of the 2.09 N Me4NOH solut~on was then added and the spectrum recorded. In general the absorbance decreased with time, as a result of reactlon of hydroxide with D M F (basic hydrolysis (20)) and extrapolation at constant h was required to obtain zero time absorbance values. Measurements were performed in duplicate.…”

Section: Methodsmentioning

confidence: 99%

The H₋ acidity function for dimethylformamide–water

Buncel¹,

Symons²,

Dolman³

et al. 1970

Can. J. Chem.

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The H-acidity function has been determined for N,N-dimethylformamide-water mixtures containing tetramethylammonium hydroxide by the Harnmett indicator method. Basicity in the aqueous dimethylformamide system exceeds that in aqueous tetran~ethylenesulfone but is slightly less than in aqueous dimethylsulfoxide, at equivalent molar compositions of solvent and base. However, the basic aqueous dimethylformamide solvent system is only of limited utility as a result of reaction of hydroxide ion with the dimethylformamide.

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“…Under these conditions, a formate ion is surmised to be generated from DMF and hydroxide, as the hydrogen donor. [32] Dehalogenation of activated aryl chlorides occurs smoothly and quantitative yields were reached within 30-40 min (entries 1 and 4, Table 2). [33] Sterically hindered 2-chloroacetophenone was converted at a slower rate and afforded 57 % acetophenone after 2 h (entry 2, Table 2).…”

mentioning

confidence: 99%

Polyoxometalate‐Based N‐Heterocyclic Carbene (NHC) Complexes for Palladium‐Mediated CC Coupling and Chloroaryl Dehalogenation Catalysis

Berardi

Carraro

Iglesias

et al. 2010

Chemistry A European J

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The inherent instability of dimethylformamide–water systems containing hydroxide ion

Cited by 41 publications

References 0 publications

Hydrogen exchange studies. XIV. Kinetics and mechanism of base-catalyzed hydrogen exchange in 1,3-dinitrobenzene in aqueous dimethylformamide and relationship with σ-complex formation

Hydrogen exchange studies. XIV. Kinetics and mechanism of base-catalyzed hydrogen exchange in 1,3-dinitrobenzene in aqueous dimethylformamide and relationship with σ-complex formation

The H₋ acidity function for dimethylformamide–water

Polyoxometalate‐Based N‐Heterocyclic Carbene (NHC) Complexes for Palladium‐Mediated CC Coupling and Chloroaryl Dehalogenation Catalysis

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The inherent instability of dimethylformamide–water systems containing hydroxide ion

Cited by 41 publications

References 0 publications

Hydrogen exchange studies. XIV. Kinetics and mechanism of base-catalyzed hydrogen exchange in 1,3-dinitrobenzene in aqueous dimethylformamide and relationship with σ-complex formation

Hydrogen exchange studies. XIV. Kinetics and mechanism of base-catalyzed hydrogen exchange in 1,3-dinitrobenzene in aqueous dimethylformamide and relationship with σ-complex formation

The H− acidity function for dimethylformamide–water

Polyoxometalate‐Based N‐Heterocyclic Carbene (NHC) Complexes for Palladium‐Mediated CC Coupling and Chloroaryl Dehalogenation Catalysis

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The H₋ acidity function for dimethylformamide–water