Kinetic and equilibrium acidities of 3-nitropropene and some of its derivatives

Bordwell, F. G.; Hautala, Judith A.

doi:10.1021/jo00410a005

Cited by 19 publications

(3 citation statements)

References 6 publications

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“…Moreover, the 366 nm chromophore is regained quantitatively upon adjusting the pH back to pH 7.8 (Figure 3B). It is known that nitronic acids are ∼2 pK a units more acidic than the corresponding nitroalkene, indicating that the concentration of the nitronic acid form would be very low and well below experimental errors (33). Finally, the conclusion that the product at low pH is 4-nitro-but-2-enoyl-CoA, rather than the corresponding nitronic acid, is supported by the fact that 1-nitroalkane is thermodynamically more stable than the corresponding nitronic acid (34).…”

Section: Resultsmentioning

confidence: 92%

“…This decrease in pK a is consistent with the assignment of the 366 nm absorbing product as the conjugated nitronate. For example, the pK a of 1-nitrobutane is 8.6 (32) while that of nitrobut-2-ene is 5.2 (33). The reduction of the pK a of the model compound and the enoyl-CoA is about 3.5-4.0 pH units when the conjugated double bond is introduced.…”

Section: Resultsmentioning

confidence: 98%

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Alternate Substrates of Human Glutaryl-CoA Dehydrogenase: Structure and Reactivity of Substrates, and Identification of a Novel 2-Enoyl-CoA Product

et al. 2002

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The dehydrogenation reaction catalyzed by human glutaryl-CoA dehydrogenase was investigated using a series of alternate substrates. These substrates have various substituents at the gamma position in place of the carboxylate of the physiological substrate, glutaryl-CoA. The steady-state kinetic constants of the six alternate substrates and the extent of flavin reduction in the anaerobic half-reaction were determined. One of these substrates, 4-nitrobutyryl-CoA, was previously thought not to be a substrate of the dehydrogenase; however, the enzyme does oxidize this substrate analogue with a k(cat) that is less than 2% of that with glutaryl-CoA when ferrocenium hexafluorophosphate (FcPF(6)) is the electron acceptor. Anaerobic titration of the dehydrogenase with 4-nitrobutyryl-CoA showed no reduction of the flavin; but instead showed an increased absorbance in the 460 nm region suggesting deprotonation of the analogue to form the alpha-carbanion. Analysis of these data indicated a binding stoichiometry of about 1.0. Under aerobic conditions, a second absorption maximum is observed with lambda(max) = 366 nm. The generation of the latter chromophore is dependent on an electron acceptor, either O(2) or FcPF(6), and is greatly facilitated by the catalytic base Glu370. The 466 nm absorbing species remains enzyme-bound while the 366 nm absorbing species is present only in solution. The latter compound was identified as 4-nitronate-but-2-enoyl-CoA by mass spectrometry, (1)H NMR, and chemical analyses. Ionization of the enzymatic product, 4-nitro-but-2-enoyl-CoA, that yields the nitronate occurs in solution and not on the enzyme. The variation of k(cat) with the nature of the substituent suggests that the various substituents affect the free energy of activation, Delta G(++), for dehydrogenation. There is a good correlation between log(k(cat)) and F, the field effect parameter, of the gamma-substituent. No correlation was found between any other kinetic or equilibrium constants and the substituent parameters using quantitative structure-activity relationships (QSAR). 4-Nitrobutyryl-CoA is the extreme example with the strongly electron-withdrawing nitro group in the gamma position.

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Section: Resultsmentioning

confidence: 92%

Section: Resultsmentioning

confidence: 98%

Alternate Substrates of Human Glutaryl-CoA Dehydrogenase: Structure and Reactivity of Substrates, and Identification of a Novel 2-Enoyl-CoA Product

et al. 2002

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“…However, it was discovered through the work of Bordwell, Jencks, Bernasconi, and others [ 42 – 46 ] that certain processes were characterized by β values out of this normal range. Most of the S N 2 reactions are characterized by β nuc values in the 0.2–0.5 range [ 42 , 43 ]. However, β nuc values close to or greater than 1.0 have been observed for other S N 2-type reactions of carbanions and nitranions with sulfonyl- and nitro-activated aromatic halides.…”

Section: Introductionmentioning

confidence: 99%

Electronic and solvent effects on kinetics of SNAr substitution reactions of substituted anilines with 2,6-bis(trifluoromethanesulfonyl)-4-nitroanisole in MeOH–Me2SO mixtures of varying composition: one reaction with two mechanistic pathways

2013

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The kinetics and mechanism of the aromatic nucleophilic substitution reactions of 2,6-bis(trifluoromethanesulfonyl)-4-nitroanisole with para-X-substituted anilines (X = OH, OMe, Me, H, F, I, Cl) were studied in MeOH–Me2SO mixtures and pure Me2SO at 25.0 °C. The second-order rate coefficients depend on the substitutent in aniline and give good Hammett and Brønsted correlations; a polar SNAr reaction is proposed for the reaction in different MeOH–Me2SO mixtures. The measured rate coefficients of the reaction demonstrated dramatic variations for aniline donor with the increasing dimethyl sulfoxide composition in MeOH–Me2SO mixtures. In this case, the Hammett and Brønsted plots are biphasic and concave upwards with a break point at 4-methylaniline. These results indicate a change in mechanism from the polar (SNAr) for less basic nucleophiles (X = 4-Cl, 4-I, 4-F, and H) to the single electron transfer (SET) for more basic nucleophiles (X = 4-OH, 4-OMe and 4-Me). The changes of the structure of the transitions states with substituents and solvent are in accordance with the results of kinetics studies. The solvation model described is well supported by the solvatochromism exhibited by aniline in the solvent mixture under investigation. These results provide an ideal framework for understanding the paramount importance of the specific molecular structure of solvent molecules in determining chemical reactivity versus solvent effects.Graphical abstractElectronic supplementary materialThe online version of this article (doi:10.1007/s00706-013-1030-7) contains supplementary material, which is available to authorized users.

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Zur Struktur der Lithiumverbindungen von Sulfonen, Sulfoximiden, Sulfoxiden, Thioethern und 1,3‐Dithianen, Nitrilen, Nitroverbindungen und Hydrazonen

Boche

1989

Angewandte Chemie

170

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Acceptor-substituierte Lithiumverbindungen LiA-CR'R', bei denen der Acceptor A eine RC(0)-, N=C-, RS02-, RS(0)NR-, RSO-, RS-, 0 2 N -oder RC(N-NR,)-Gruppe sein kann, spielen in der organischen Synthese seit langem eine gro13e Rolle. Ihre Bedeutung ist in den letzten fiinfzehn Jahren nochmals gestiegen, nachdem man in zunehmendem Ma13 gelernt hatte, sie in chemo-, regio-, diastereo-und enantioselektiven Reaktionen einzusetzen. Dabei ist bemerkenswert, dal3 man iiber die Strukturen von solchen Verbindungen, wenn iiberhaupt etwas, meist nur wenig wul3te. Es wundert daher nicht, dal3 das Interesse daran in jungster Zeit stark zugenornmen hat. Im folgenden werden die neueren Untersuchungen zur Struktur der Lithiumverbindungen von Sulfonen, Sulfoximiden, Sulfoxiden, Thioethern und 1,3-Dithianen, Nitrilen, Nitroverbindungen und Hydrazonen zusammengefal3t. Die Festkorperstrukturuntersuchungen der letzten Jahre stehen dabei im Mittelpunkt. Sie werden erganzt durch Untersuchungen in Losung und durch Strukturberechnungen. Wo es moglich ist, wird auf strukturelle Verwandtschaften und Unterschiede zwischen den einzelnen Aggregatzustanden und auf den Zusammenhang zwischen Struktur und Reaktivitat hingewiesen.

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Kinetic and equilibrium acidities of 3-nitropropene and some of its derivatives

Cited by 19 publications

References 6 publications

Alternate Substrates of Human Glutaryl-CoA Dehydrogenase: Structure and Reactivity of Substrates, and Identification of a Novel 2-Enoyl-CoA Product

Alternate Substrates of Human Glutaryl-CoA Dehydrogenase: Structure and Reactivity of Substrates, and Identification of a Novel 2-Enoyl-CoA Product

Electronic and solvent effects on kinetics of SNAr substitution reactions of substituted anilines with 2,6-bis(trifluoromethanesulfonyl)-4-nitroanisole in MeOH–Me2SO mixtures of varying composition: one reaction with two mechanistic pathways

Zur Struktur der Lithiumverbindungen von Sulfonen, Sulfoximiden, Sulfoxiden, Thioethern und 1,3‐Dithianen, Nitrilen, Nitroverbindungen und Hydrazonen

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