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Athula B. Attygalle - One of the best experts on this subject based on the ideXlab platform.
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Competitive Deprotonation and Superoxide [O_2 ^-•] Radical-Anion Adduct Formation Reactions of Carboxamides under Negative-Ion Atmospheric-Pressure Helium-Plasma Ionization (HePI) Conditions
Journal of The American Society for Mass Spectrometry, 2016Co-Authors: Isra Hassan, Spencer Pinto, Carl Weisbecker, Athula B. AttygalleAbstract:Carboxamides bearing an N–H functionality are known to undergo deprotonation under negative-ion-generating mass spectrometric conditions. Herein, we report that N–H bearing carboxamides with acidities lower than that of the Hydroperoxyl radical (HO-O^•) preferentially form superoxide radical-anion (O_2 ^-•) adducts, rather than deprotonate, when they are exposed to the glow discharge of a helium-plasma ionization source. For example, the spectra of N -alkylacetamides show peaks for superoxide radical-anion (O_2 ^-•) adducts. Conversely, more acidic amides, such as N -alkyltrifluoroacetamides, preferentially undergo deprotonation under similar experimental conditions. Upon collisional activation, the O_2 ^-• adducts of N -alkylacetamides either lose the neutral amide or the Hydroperoxyl radical (HO-O^•) to generate the superoxide radical-anion ( m/z 32) or the deprotonated amide [ m/z (M – H)^−], respectively. For somewhat acidic carboxamides, the association between the two entities is weak. Thus, upon mildest collisional activation, the adduct dissociates to eject the superoxide anion. Superoxide-adduct formation results are useful for structure determination purposes because carboxamides devoid of a N–H functionality undergo neither deprotonation nor adduct formation under HePI conditions. Graphical Abstract ᅟ
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Competitive Deprotonation and Superoxide [O2-•] Radical-Anion Adduct Formation Reactions of Carboxamides under Negative-Ion Atmospheric-Pressure Helium-Plasma Ionization (HePI) Conditions
Journal of the American Society for Mass Spectrometry, 2015Co-Authors: Isra Hassan, Spencer Pinto, Carl Weisbecker, Athula B. AttygalleAbstract:Carboxamides bearing an N-H functionality are known to undergo deprotonation under negative-ion-generating mass spectrometric conditions. Herein, we report that N-H bearing carboxamides with acidities lower than that of the Hydroperoxyl radical (HO-O(•)) preferentially form superoxide radical-anion (O2(-•)) adducts, rather than deprotonate, when they are exposed to the glow discharge of a helium-plasma ionization source. For example, the spectra of N-alkylacetamides show peaks for superoxide radical-anion (O2(-•)) adducts. Conversely, more acidic amides, such as N-alkyltrifluoroacetamides, preferentially undergo deprotonation under similar experimental conditions. Upon collisional activation, the O2(-•) adducts of N-alkylacetamides either lose the neutral amide or the Hydroperoxyl radical (HO-O(•)) to generate the superoxide radical-anion (m/z 32) or the deprotonated amide [m/z (M - H)(-)], respectively. For somewhat acidic carboxamides, the association between the two entities is weak. Thus, upon mildest collisional activation, the adduct dissociates to eject the superoxide anion. Superoxide-adduct formation results are useful for structure determination purposes because carboxamides devoid of a N-H functionality undergo neither deprotonation nor adduct formation under HePI conditions.
Isra Hassan - One of the best experts on this subject based on the ideXlab platform.
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Competitive Deprotonation and Superoxide [O_2 ^-•] Radical-Anion Adduct Formation Reactions of Carboxamides under Negative-Ion Atmospheric-Pressure Helium-Plasma Ionization (HePI) Conditions
Journal of The American Society for Mass Spectrometry, 2016Co-Authors: Isra Hassan, Spencer Pinto, Carl Weisbecker, Athula B. AttygalleAbstract:Carboxamides bearing an N–H functionality are known to undergo deprotonation under negative-ion-generating mass spectrometric conditions. Herein, we report that N–H bearing carboxamides with acidities lower than that of the Hydroperoxyl radical (HO-O^•) preferentially form superoxide radical-anion (O_2 ^-•) adducts, rather than deprotonate, when they are exposed to the glow discharge of a helium-plasma ionization source. For example, the spectra of N -alkylacetamides show peaks for superoxide radical-anion (O_2 ^-•) adducts. Conversely, more acidic amides, such as N -alkyltrifluoroacetamides, preferentially undergo deprotonation under similar experimental conditions. Upon collisional activation, the O_2 ^-• adducts of N -alkylacetamides either lose the neutral amide or the Hydroperoxyl radical (HO-O^•) to generate the superoxide radical-anion ( m/z 32) or the deprotonated amide [ m/z (M – H)^−], respectively. For somewhat acidic carboxamides, the association between the two entities is weak. Thus, upon mildest collisional activation, the adduct dissociates to eject the superoxide anion. Superoxide-adduct formation results are useful for structure determination purposes because carboxamides devoid of a N–H functionality undergo neither deprotonation nor adduct formation under HePI conditions. Graphical Abstract ᅟ
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Competitive Deprotonation and Superoxide [O2-•] Radical-Anion Adduct Formation Reactions of Carboxamides under Negative-Ion Atmospheric-Pressure Helium-Plasma Ionization (HePI) Conditions
Journal of the American Society for Mass Spectrometry, 2015Co-Authors: Isra Hassan, Spencer Pinto, Carl Weisbecker, Athula B. AttygalleAbstract:Carboxamides bearing an N-H functionality are known to undergo deprotonation under negative-ion-generating mass spectrometric conditions. Herein, we report that N-H bearing carboxamides with acidities lower than that of the Hydroperoxyl radical (HO-O(•)) preferentially form superoxide radical-anion (O2(-•)) adducts, rather than deprotonate, when they are exposed to the glow discharge of a helium-plasma ionization source. For example, the spectra of N-alkylacetamides show peaks for superoxide radical-anion (O2(-•)) adducts. Conversely, more acidic amides, such as N-alkyltrifluoroacetamides, preferentially undergo deprotonation under similar experimental conditions. Upon collisional activation, the O2(-•) adducts of N-alkylacetamides either lose the neutral amide or the Hydroperoxyl radical (HO-O(•)) to generate the superoxide radical-anion (m/z 32) or the deprotonated amide [m/z (M - H)(-)], respectively. For somewhat acidic carboxamides, the association between the two entities is weak. Thus, upon mildest collisional activation, the adduct dissociates to eject the superoxide anion. Superoxide-adduct formation results are useful for structure determination purposes because carboxamides devoid of a N-H functionality undergo neither deprotonation nor adduct formation under HePI conditions.
Spencer Pinto - One of the best experts on this subject based on the ideXlab platform.
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Competitive Deprotonation and Superoxide [O_2 ^-•] Radical-Anion Adduct Formation Reactions of Carboxamides under Negative-Ion Atmospheric-Pressure Helium-Plasma Ionization (HePI) Conditions
Journal of The American Society for Mass Spectrometry, 2016Co-Authors: Isra Hassan, Spencer Pinto, Carl Weisbecker, Athula B. AttygalleAbstract:Carboxamides bearing an N–H functionality are known to undergo deprotonation under negative-ion-generating mass spectrometric conditions. Herein, we report that N–H bearing carboxamides with acidities lower than that of the Hydroperoxyl radical (HO-O^•) preferentially form superoxide radical-anion (O_2 ^-•) adducts, rather than deprotonate, when they are exposed to the glow discharge of a helium-plasma ionization source. For example, the spectra of N -alkylacetamides show peaks for superoxide radical-anion (O_2 ^-•) adducts. Conversely, more acidic amides, such as N -alkyltrifluoroacetamides, preferentially undergo deprotonation under similar experimental conditions. Upon collisional activation, the O_2 ^-• adducts of N -alkylacetamides either lose the neutral amide or the Hydroperoxyl radical (HO-O^•) to generate the superoxide radical-anion ( m/z 32) or the deprotonated amide [ m/z (M – H)^−], respectively. For somewhat acidic carboxamides, the association between the two entities is weak. Thus, upon mildest collisional activation, the adduct dissociates to eject the superoxide anion. Superoxide-adduct formation results are useful for structure determination purposes because carboxamides devoid of a N–H functionality undergo neither deprotonation nor adduct formation under HePI conditions. Graphical Abstract ᅟ
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Competitive Deprotonation and Superoxide [O2-•] Radical-Anion Adduct Formation Reactions of Carboxamides under Negative-Ion Atmospheric-Pressure Helium-Plasma Ionization (HePI) Conditions
Journal of the American Society for Mass Spectrometry, 2015Co-Authors: Isra Hassan, Spencer Pinto, Carl Weisbecker, Athula B. AttygalleAbstract:Carboxamides bearing an N-H functionality are known to undergo deprotonation under negative-ion-generating mass spectrometric conditions. Herein, we report that N-H bearing carboxamides with acidities lower than that of the Hydroperoxyl radical (HO-O(•)) preferentially form superoxide radical-anion (O2(-•)) adducts, rather than deprotonate, when they are exposed to the glow discharge of a helium-plasma ionization source. For example, the spectra of N-alkylacetamides show peaks for superoxide radical-anion (O2(-•)) adducts. Conversely, more acidic amides, such as N-alkyltrifluoroacetamides, preferentially undergo deprotonation under similar experimental conditions. Upon collisional activation, the O2(-•) adducts of N-alkylacetamides either lose the neutral amide or the Hydroperoxyl radical (HO-O(•)) to generate the superoxide radical-anion (m/z 32) or the deprotonated amide [m/z (M - H)(-)], respectively. For somewhat acidic carboxamides, the association between the two entities is weak. Thus, upon mildest collisional activation, the adduct dissociates to eject the superoxide anion. Superoxide-adduct formation results are useful for structure determination purposes because carboxamides devoid of a N-H functionality undergo neither deprotonation nor adduct formation under HePI conditions.
Carl Weisbecker - One of the best experts on this subject based on the ideXlab platform.
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Competitive Deprotonation and Superoxide [O_2 ^-•] Radical-Anion Adduct Formation Reactions of Carboxamides under Negative-Ion Atmospheric-Pressure Helium-Plasma Ionization (HePI) Conditions
Journal of The American Society for Mass Spectrometry, 2016Co-Authors: Isra Hassan, Spencer Pinto, Carl Weisbecker, Athula B. AttygalleAbstract:Carboxamides bearing an N–H functionality are known to undergo deprotonation under negative-ion-generating mass spectrometric conditions. Herein, we report that N–H bearing carboxamides with acidities lower than that of the Hydroperoxyl radical (HO-O^•) preferentially form superoxide radical-anion (O_2 ^-•) adducts, rather than deprotonate, when they are exposed to the glow discharge of a helium-plasma ionization source. For example, the spectra of N -alkylacetamides show peaks for superoxide radical-anion (O_2 ^-•) adducts. Conversely, more acidic amides, such as N -alkyltrifluoroacetamides, preferentially undergo deprotonation under similar experimental conditions. Upon collisional activation, the O_2 ^-• adducts of N -alkylacetamides either lose the neutral amide or the Hydroperoxyl radical (HO-O^•) to generate the superoxide radical-anion ( m/z 32) or the deprotonated amide [ m/z (M – H)^−], respectively. For somewhat acidic carboxamides, the association between the two entities is weak. Thus, upon mildest collisional activation, the adduct dissociates to eject the superoxide anion. Superoxide-adduct formation results are useful for structure determination purposes because carboxamides devoid of a N–H functionality undergo neither deprotonation nor adduct formation under HePI conditions. Graphical Abstract ᅟ
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Competitive Deprotonation and Superoxide [O2-•] Radical-Anion Adduct Formation Reactions of Carboxamides under Negative-Ion Atmospheric-Pressure Helium-Plasma Ionization (HePI) Conditions
Journal of the American Society for Mass Spectrometry, 2015Co-Authors: Isra Hassan, Spencer Pinto, Carl Weisbecker, Athula B. AttygalleAbstract:Carboxamides bearing an N-H functionality are known to undergo deprotonation under negative-ion-generating mass spectrometric conditions. Herein, we report that N-H bearing carboxamides with acidities lower than that of the Hydroperoxyl radical (HO-O(•)) preferentially form superoxide radical-anion (O2(-•)) adducts, rather than deprotonate, when they are exposed to the glow discharge of a helium-plasma ionization source. For example, the spectra of N-alkylacetamides show peaks for superoxide radical-anion (O2(-•)) adducts. Conversely, more acidic amides, such as N-alkyltrifluoroacetamides, preferentially undergo deprotonation under similar experimental conditions. Upon collisional activation, the O2(-•) adducts of N-alkylacetamides either lose the neutral amide or the Hydroperoxyl radical (HO-O(•)) to generate the superoxide radical-anion (m/z 32) or the deprotonated amide [m/z (M - H)(-)], respectively. For somewhat acidic carboxamides, the association between the two entities is weak. Thus, upon mildest collisional activation, the adduct dissociates to eject the superoxide anion. Superoxide-adduct formation results are useful for structure determination purposes because carboxamides devoid of a N-H functionality undergo neither deprotonation nor adduct formation under HePI conditions.
Joseph S. Francisco - One of the best experts on this subject based on the ideXlab platform.
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Can Urea Be a Seed for Aerosol Particle Formation in Air
The journal of physical chemistry. A, 2018Co-Authors: Manoj Kumar, Tarek Trabelsi, Joseph S. FranciscoAbstract:Urea is ubiquitous in rainwaters and aqueous aerosols in different environments. However, its atmospheric fate and the exact mechanism on how it influences new particle formation remain completely unexplored. Herein, we have used quantum chemical calculations and Born–Oppenheimer molecular dynamics simulations to explore the potential role of urea in the particle formation events. The results suggest that urea binds more strongly to common acidic precursors than ammonia or monoamines and is capable of binding at most two molecules of an acidic precursor or Hydroperoxyl radical via hydrogen bonding interactions. The molecular dynamics simulations suggest that the complex of urea with an acidic precursor or Hydroperoxyl radical on the water droplet is stabilized by intermolecular and interfacial hydrogen bonding interactions over the simulation time scale of 10–15 ps. An important implication of these results is that urea may contribute toward the particle formation in marine environments as well as in Asia...
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Can Urea Be a Seed for Aerosol Particle Formation in Air?
2018Co-Authors: Manoj Kumar, Tarek Trabelsi, Joseph S. FranciscoAbstract:Urea is ubiquitous in rainwaters and aqueous aerosols in different environments. However, its atmospheric fate and the exact mechanism on how it influences new particle formation remain completely unexplored. Herein, we have used quantum chemical calculations and Born–Oppenheimer molecular dynamics simulations to explore the potential role of urea in the particle formation events. The results suggest that urea binds more strongly to common acidic precursors than ammonia or monoamines and is capable of binding at most two molecules of an acidic precursor or Hydroperoxyl radical via hydrogen bonding interactions. The molecular dynamics simulations suggest that the complex of urea with an acidic precursor or Hydroperoxyl radical on the water droplet is stabilized by intermolecular and interfacial hydrogen bonding interactions over the simulation time scale of 10–15 ps. An important implication of these results is that urea may contribute toward the particle formation in marine environments as well as in Asia where the usage of urea for the agricultural activities has increased dramatically over last few decades. Though there is at the moment no evidence of urea being present in the atmospheric gas-phase, we hope our work would inspire field measurements for detecting urea in the gas-phase
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Complexes of Hydroperoxyl Radical with Glyoxal, Methylglyoxal, Methylvinyl Ketone, Acrolein, and Methacrolein: Possible New Sinks for HO2 in the Atmosphere?
The Journal of Physical Chemistry A, 2003Co-Authors: Simone Aloisio, Joseph S. FranciscoAbstract:Structures and energetics of complexes of HO2 with glyoxal, methylglyoxal, methylvinyl ketone, and methacrolein have been calculated using density functional theory. The hydroperoxy radical was fou...
