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John E. T. Corrie - One of the best experts on this subject based on the ideXlab platform.
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kinetics of proton release after flash photolysis of 1 2 nitrophenyl ethyl sulfate caged sulfate in aqueous solution
Journal of the American Chemical Society, 2005Co-Authors: Stefania Abbruzzetti, Stefano Sottini, Cristiano Viappiani, John E. T. CorrieAbstract:The kinetics of proton release after laser photolysis of 1-(2-nitrophenyl)ethyl sulfate (caged sulfate) have been characterized by time-resolved absorbance and photoacoustic methods. The absorbance at ∼400 nm is observed to rise with a biphasic behavior in which a prompt component (formation of the Nitronic acid) is followed by a slower (τ ≈ 63 ± 6 ns) phase (deprotonation of the Nitronic acid). The decay of this intermediate occurs with a lifetime which is affected by the pH of the solution and the laser pulse energy. In buffered aqueous solution at pH 7, 20 °C the aci-nitro decay rate is 18 ± 4 s-1. Protons are released to the solution with rate (1.58 ± 0.09) × 107 s-1 at neutral pH from the Nitronic acid intermediate. From the numerical analysis of the protonation kinetics of suitable pH indicators, we could estimate the pKa of the Nitronic acid as 3.69 ± 0.05. At acidic pH, a substantial fraction of the aci-nitro intermediate is in the protonated form and this leads to a biphasic release of protons, w...
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Kinetics of proton release after flash photolysis of 1-(2-nitrophenyl)ethyl sulfate (caged sulfate) in aqueous solution
2005Co-Authors: Abbruzzetti S., Stefano Sottini, Cristiano Viappiani, John E. T. CorrieAbstract:The kinetics of proton release after laser photolysis of 1-(2-nitrophenyl)ethyl sulfate (caged sulfate) have been characterized by time-resolved absorbance and photoacoustic methods. The absorbance at approximately 400 nm is observed to rise with a biphasic behavior in which a prompt component (formation of the Nitronic acid) is followed by a slower (tau approximately 63 +/- 6 ns) phase (deprotonation of the Nitronic acid). The decay of this intermediate occurs with a lifetime which is affected by the pH of the solution and the laser pulse energy. In buffered aqueous solution at pH 7, 20 degrees C the aci-nitro decay rate is 18 +/- 4 s(-1). Protons are released to the solution with rate (1.58 +/- 0.09) x 10(7) s(-1) at neutral pH from the Nitronic acid intermediate. From the numerical analysis of the protonation kinetics of suitable pH indicators, we could estimate the pK(a) of the Nitronic acid as 3.69 +/- 0.05. At acidic pH, a substantial fraction of the aci-nitro intermediate is in the protonated form and this leads to a biphasic release of protons, with the slower phase being characterized by an apparent rate constant strongly dependent on the pH. The strongly acidic character of the final photoproduct (sulfate ion) means that there is negligible buffering of photoreleased protons
Stefania Abbruzzetti - One of the best experts on this subject based on the ideXlab platform.
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kinetics of proton release after flash photolysis of 1 2 nitrophenyl ethyl sulfate caged sulfate in aqueous solution
Journal of the American Chemical Society, 2005Co-Authors: Stefania Abbruzzetti, Stefano Sottini, Cristiano Viappiani, John E. T. CorrieAbstract:The kinetics of proton release after laser photolysis of 1-(2-nitrophenyl)ethyl sulfate (caged sulfate) have been characterized by time-resolved absorbance and photoacoustic methods. The absorbance at ∼400 nm is observed to rise with a biphasic behavior in which a prompt component (formation of the Nitronic acid) is followed by a slower (τ ≈ 63 ± 6 ns) phase (deprotonation of the Nitronic acid). The decay of this intermediate occurs with a lifetime which is affected by the pH of the solution and the laser pulse energy. In buffered aqueous solution at pH 7, 20 °C the aci-nitro decay rate is 18 ± 4 s-1. Protons are released to the solution with rate (1.58 ± 0.09) × 107 s-1 at neutral pH from the Nitronic acid intermediate. From the numerical analysis of the protonation kinetics of suitable pH indicators, we could estimate the pKa of the Nitronic acid as 3.69 ± 0.05. At acidic pH, a substantial fraction of the aci-nitro intermediate is in the protonated form and this leads to a biphasic release of protons, w...
Cheng-lie Yin - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and Characterization of Chiral Nitronic Esters via O- Alkylation of (4S*,5R)-(+)-4-(1′-Nitro-1′-carbethoxymethyl)-5-((1R)- menthyloxy)-3,4-dihydro-2(5H)-furanone with Alkyl Halides.
ChemInform, 2010Co-Authors: Fu-an Kang, Cheng-lie Yin, Shi-wang SheAbstract:A series of stable and enantiomerically pure alkyl Nitronic esters are synthesized in good to excellent yields via O-alkylation of (4S*,5R)-(+)-4-(1‘-nitro-1‘-carbethoxymethyl)-5-[(1R)-menthyloxy]-3,4-dihydro-2(5H)-furanone (4a) with alkyl halides in the presence of K2CO3 and DMF at room temperature. Thus, Nitronic esters are obtained for the first time from the alkali metal salt of a nitro compound and various alkyl halides, which refutes the traditionally held view that the reaction of alkyl halides with alkali metal derivatives of nitro compounds gives a carbonyl compound and an oxime, rather than a Nitronic ester. Secondary alkyl Nitronic esters are found to partially decompose into O-alkyloximes. The configurations of the Nitronic esters and O-alkyloximes were assigned to be Z on the basis of the NOE experiments. The synthesis of the nitro furanone 4a and its enolization to form a six-membered intramolecular hydrogen bond structure are described.
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Correlation between structure and stability of Nitronic acids and Nitronic esters
Science China-chemistry, 1998Co-Authors: Fu’an Kang, Cheng-lie YinAbstract:On the basis of investigation on structural characteristics and stability of more than one hundred Nitronic acids and Nitronic esters, an equilibrium theory of electronic effects in conjugated systems is put forward and the type of structures is classified. On that basis, an empirical rule for the correlation between structure and stability of Nitronic acids and Nitronic esters is proposed, which predicts that stable Nitronic acids and Nitronic esters should have the C type of structure that meets the matching principle of electronic effects.
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Studies on the chemistry of the chiral Nitronic acid and Nitronic esters
Tetrahedron: Asymmetry, 1997Co-Authors: Fu-an Kang, Cheng-lie YinAbstract:Abstract Some new chemistry of the chiral Nitronic acid and Nitronic esters is described. Conversions with retention of configuration are found among the chiral Nitronic acid, oxime, Nitronic esters and O -alkyloximes. α,β-Elimination reactions of Nitronic esters are observed for the first time. Novel and enantiopure chiral bisheterocyclic compounds are obtained via highly diastereoselective 1,3-dipolar cycloaddition of the chiral Nitronic esters with ethyl acrylate.
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O- and C-alkylations of ethyl nitroacetate with benzyl halides
Chinese Science Bulletin, 1997Co-Authors: Fu’an Kang, Hong-yi Yin, Cheng-lie YinAbstract:THE chemistry of Nitronic esters remains relatively unknown due to their conspicuous feature ofinstability. In the preceding papers, we described the late progress in the researchof Nitronic esters: (i) Nitronic esters were first synthesized via O-alkylation of the alkali met-...
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synthesis and characterization of chiral Nitronic esters via o alkylation of 4s 5r 4 1 nitro 1 carbethoxymethyl 5 1r menthyloxy 3 4 dihydro 2 5h furanone with alkyl halides
Journal of Organic Chemistry, 1996Co-Authors: Fu-an Kang, Cheng-lie Yin, Shi-wang SheAbstract:A series of stable and enantiomerically pure alkyl Nitronic esters are synthesized in good to excellent yields via O-alkylation of (4S*,5R)-(+)-4-(1‘-nitro-1‘-carbethoxymethyl)-5-[(1R)-menthyloxy]-3,4-dihydro-2(5H)-furanone (4a) with alkyl halides in the presence of K2CO3 and DMF at room temperature. Thus, Nitronic esters are obtained for the first time from the alkali metal salt of a nitro compound and various alkyl halides, which refutes the traditionally held view that the reaction of alkyl halides with alkali metal derivatives of nitro compounds gives a carbonyl compound and an oxime, rather than a Nitronic ester. Secondary alkyl Nitronic esters are found to partially decompose into O-alkyloximes. The configurations of the Nitronic esters and O-alkyloximes were assigned to be Z on the basis of the NOE experiments. The synthesis of the nitro furanone 4a and its enolization to form a six-membered intramolecular hydrogen bond structure are described.
Cristiano Viappiani - One of the best experts on this subject based on the ideXlab platform.
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kinetics of proton release after flash photolysis of 1 2 nitrophenyl ethyl sulfate caged sulfate in aqueous solution
Journal of the American Chemical Society, 2005Co-Authors: Stefania Abbruzzetti, Stefano Sottini, Cristiano Viappiani, John E. T. CorrieAbstract:The kinetics of proton release after laser photolysis of 1-(2-nitrophenyl)ethyl sulfate (caged sulfate) have been characterized by time-resolved absorbance and photoacoustic methods. The absorbance at ∼400 nm is observed to rise with a biphasic behavior in which a prompt component (formation of the Nitronic acid) is followed by a slower (τ ≈ 63 ± 6 ns) phase (deprotonation of the Nitronic acid). The decay of this intermediate occurs with a lifetime which is affected by the pH of the solution and the laser pulse energy. In buffered aqueous solution at pH 7, 20 °C the aci-nitro decay rate is 18 ± 4 s-1. Protons are released to the solution with rate (1.58 ± 0.09) × 107 s-1 at neutral pH from the Nitronic acid intermediate. From the numerical analysis of the protonation kinetics of suitable pH indicators, we could estimate the pKa of the Nitronic acid as 3.69 ± 0.05. At acidic pH, a substantial fraction of the aci-nitro intermediate is in the protonated form and this leads to a biphasic release of protons, w...
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Kinetics of proton release after flash photolysis of 1-(2-nitrophenyl)ethyl sulfate (caged sulfate) in aqueous solution
2005Co-Authors: Abbruzzetti S., Stefano Sottini, Cristiano Viappiani, John E. T. CorrieAbstract:The kinetics of proton release after laser photolysis of 1-(2-nitrophenyl)ethyl sulfate (caged sulfate) have been characterized by time-resolved absorbance and photoacoustic methods. The absorbance at approximately 400 nm is observed to rise with a biphasic behavior in which a prompt component (formation of the Nitronic acid) is followed by a slower (tau approximately 63 +/- 6 ns) phase (deprotonation of the Nitronic acid). The decay of this intermediate occurs with a lifetime which is affected by the pH of the solution and the laser pulse energy. In buffered aqueous solution at pH 7, 20 degrees C the aci-nitro decay rate is 18 +/- 4 s(-1). Protons are released to the solution with rate (1.58 +/- 0.09) x 10(7) s(-1) at neutral pH from the Nitronic acid intermediate. From the numerical analysis of the protonation kinetics of suitable pH indicators, we could estimate the pK(a) of the Nitronic acid as 3.69 +/- 0.05. At acidic pH, a substantial fraction of the aci-nitro intermediate is in the protonated form and this leads to a biphasic release of protons, with the slower phase being characterized by an apparent rate constant strongly dependent on the pH. The strongly acidic character of the final photoproduct (sulfate ion) means that there is negligible buffering of photoreleased protons
Stefano Sottini - One of the best experts on this subject based on the ideXlab platform.
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kinetics of proton release after flash photolysis of 1 2 nitrophenyl ethyl sulfate caged sulfate in aqueous solution
Journal of the American Chemical Society, 2005Co-Authors: Stefania Abbruzzetti, Stefano Sottini, Cristiano Viappiani, John E. T. CorrieAbstract:The kinetics of proton release after laser photolysis of 1-(2-nitrophenyl)ethyl sulfate (caged sulfate) have been characterized by time-resolved absorbance and photoacoustic methods. The absorbance at ∼400 nm is observed to rise with a biphasic behavior in which a prompt component (formation of the Nitronic acid) is followed by a slower (τ ≈ 63 ± 6 ns) phase (deprotonation of the Nitronic acid). The decay of this intermediate occurs with a lifetime which is affected by the pH of the solution and the laser pulse energy. In buffered aqueous solution at pH 7, 20 °C the aci-nitro decay rate is 18 ± 4 s-1. Protons are released to the solution with rate (1.58 ± 0.09) × 107 s-1 at neutral pH from the Nitronic acid intermediate. From the numerical analysis of the protonation kinetics of suitable pH indicators, we could estimate the pKa of the Nitronic acid as 3.69 ± 0.05. At acidic pH, a substantial fraction of the aci-nitro intermediate is in the protonated form and this leads to a biphasic release of protons, w...
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Kinetics of proton release after flash photolysis of 1-(2-nitrophenyl)ethyl sulfate (caged sulfate) in aqueous solution
2005Co-Authors: Abbruzzetti S., Stefano Sottini, Cristiano Viappiani, John E. T. CorrieAbstract:The kinetics of proton release after laser photolysis of 1-(2-nitrophenyl)ethyl sulfate (caged sulfate) have been characterized by time-resolved absorbance and photoacoustic methods. The absorbance at approximately 400 nm is observed to rise with a biphasic behavior in which a prompt component (formation of the Nitronic acid) is followed by a slower (tau approximately 63 +/- 6 ns) phase (deprotonation of the Nitronic acid). The decay of this intermediate occurs with a lifetime which is affected by the pH of the solution and the laser pulse energy. In buffered aqueous solution at pH 7, 20 degrees C the aci-nitro decay rate is 18 +/- 4 s(-1). Protons are released to the solution with rate (1.58 +/- 0.09) x 10(7) s(-1) at neutral pH from the Nitronic acid intermediate. From the numerical analysis of the protonation kinetics of suitable pH indicators, we could estimate the pK(a) of the Nitronic acid as 3.69 +/- 0.05. At acidic pH, a substantial fraction of the aci-nitro intermediate is in the protonated form and this leads to a biphasic release of protons, with the slower phase being characterized by an apparent rate constant strongly dependent on the pH. The strongly acidic character of the final photoproduct (sulfate ion) means that there is negligible buffering of photoreleased protons