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Augusto Rastelli - One of the best experts on this subject based on the ideXlab platform.
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Peroxy Acid epoxidation of acyclic allylic alcohols competition between s trans and s cis Peroxy Acid conformers
Journal of Organic Chemistry, 2005Co-Authors: Mauro Freccero, Remo Gandolfi, Mirko Sarziamade, Augusto RastelliAbstract:RB3LYP calculations, reported here, indicate that Peroxy Acid s-cis conformer is more stable than its s-trans counterpart, in agreement with experimental data. Difference in stability is the highest in the gas phase, but it falls considerably on going from the gas phase to moderately polar solvent. In the case of Peroxy formic Acid, the enthalpy (free energy) difference is about 3.4 (2.5) kcal/mol, respectively, in the gas phase but decreases to 1.2 (0.6) kcal/mol in dichloromethane solution. Introduction of an alkyl or aryl substituent on the Peroxy Acid, that is, on passing to Peroxy acetic, Peroxy benzoic (PBA), and m-chloroPeroxy benzoic Acid (MCPBA), adds a further significant (1.0−1.5 kcal/mol) favor to the s-cis isomer. RB3LYP/6-31+G(2d,p) calculations on the epoxidation of 2-propenol with Peroxy formic and Peroxy benzoic Acids, respectively, suggest that the less stable Peroxy Acid s-trans conformer can compete with the more stable s-cis form in epoxidation reaction of these substrates. Transition...
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new paradigms for the Peroxy Acid epoxidation of cc double bonds the role of the Peroxy Acid s trans conformer and of the 1 2 h transfer in the epoxidation of cyclic allylic alcohols
Journal of Organic Chemistry, 2004Co-Authors: Mauro Freccero, Remo Gandolfi, Mirko Sarziamade, Augusto RastelliAbstract:RB3LYP calculations, on reaction of performic Acid with cyclic allylic alcohols, demonstrate that the less stable s-trans conformer of Peroxy Acids can be involved in epoxidations of C=C bonds. Transition structures (TSs) arising from s-trans performic Acid retain some of the well-established characteristics of the TSs of the s-cis isomer such as the perpendicular orientation of the O-H Peroxy Acid bond relative to the C=C bond and a one-step oxirane ring formation. These TSs are very asynchronous but collapse directly (without formation of any intermediate) to the final epoxide-Peroxy Acid complex via a 1,2-H shift. Thus, our findings challenge the traditional mechanism of Peroxy Acid epoxidation of C=C bonds by demonstrating that the involvement of the s-trans isomer opens an alternative one-step reaction channel characterized by a 1,2-H transfer. This novel reaction pathway can even overcome, in the case of the reaction of cyclic allylic alcohols in moderately polar solvents (e.g., in dichloromethane), the classical Bartlett's mechanism that is based on the s-cis Peroxy Acid form and that features a 1,4-H shift. However, the latter mechanism remains strongly favored for the epoxidation of normal alkenes.
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competition between Peroxy Acid oxygens as hydrogen bond acceptors in b3lyp transition structures for epoxidations of allylic alcohols with Peroxyformic Acid
Journal of Organic Chemistry, 1999Co-Authors: Mauro Freccero, Remo Gandolfi, Mirko Sarziamade And, Augusto RastelliAbstract:The transition structures (TSs) for the epoxidation of 2-propen-1-ol and 2-cyclobuten-1-ol with Peroxyformic Acid have been located with the B3LYP method using three basis sets (i.e., 6-31G*, 6-311G**, and 6-311+G**). Syn attacks on these alcohols by Peroxy Acid lead to syn TSs in which hydrogen bonding is operative. The allylic OH group always acts as hydrogen-bond donor while either the carbonyl oxygen or the peroxo oxygens of the Peroxy Acid can play the role of hydrogen-bond acceptors. In the case of propenol, the two syn TSs (O−C−CC dihedral angles: 135.0° and 16.0°, respectively) with the peroxo oxygens involved in hydrogen bonding have free enthalpies comparable with those of their counterparts (O−C−CC dihedral angles: 134.0° and 16.3°, respectively) with hydrogen bonding to carbonyl oxygen. Basis set extension as well as electrostatic solvation effects favor the former TSs over the latter ones. In the case of cyclobutenol the syn TS (O−C−CC dihedral angle = 124.2°) with hydrogen bonding to perox...
Marianne C Nyman - One of the best experts on this subject based on the ideXlab platform.
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oxidation of pahs in a simplified system using Peroxy Acid and glass beads identification of oxidizing species
Journal of Environmental Science and Health Part A-toxic\ hazardous Substances & Environmental Engineering, 2009Co-Authors: Norman S Alderman, Marianne C NymanAbstract:Polycyclic aromatic hydrocarbons (PAHs) are organic contaminants of concern due to their ubiquity, persistence in the natural environment and adverse health effects. Numerous studies have looked into the removal and treatment of these contaminants, with mixed results. High molecular weight PAHs have been particularly problematic due to their hydrophobicity and high affinity for organics, resulting in mass transfer limitations for even the fastest advanced oxidation processes (AOPs). The Peroxy-Acid process has been used to successfully treat PAH contaminated matrices. Experiments were conducted on benzo[a]pyrene contaminated glass beads in order to elucidate the reaction mechanisms responsible for the effectiveness of this process. For the first time peracetic Acid (PAA) was identified as the important oxidant in this reaction. Different v/v/v ratios of hydrogen peroxide/acetic Acid/DI water were studied which illustrated the importance of reaction ratio on oxidant concentration and rate of formation. App...
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effective treatment of pah contaminated superfund site soil with the Peroxy Acid process
Journal of Hazardous Materials, 2007Co-Authors: Scott N Alderman, Adeola L Nguessan, Marianne C NymanAbstract:Peroxy-organic Acids are formed by the chemical reaction between organic Acids and hydrogen peroxide. The Peroxy-Acid process was applied to two Superfund site soils provided by the U.S. Environmental Protection Agency (EPA). Initial small-scale experiments applied ratios of 3:5:7 (v/v/v) or 3:3:9 (v/v/v) hydrogen peroxide:acetic Acid:deionized (DI) water solution to 5 g of Superfund site soil. The experiment using 3:5:7 (v/v/v) ratio resulted in an almost complete degradation of the 14 EPA regulated polycyclic aromatic hydrocarbons (PAHs) in Bedford LT soil during a 24-h reaction period, while the 3:3:9 (v/v/v) ratio resulted in no applicable degradation in Bedford LT lot 10 soil over the same reaction period. Specific Superfund site soil characteristics (e.g., pH, total organic carbon content and particle size distribution) were found to play an important role in the availability of the PAHs and the efficiency of the transformation during the Peroxy-Acid process. A scaled-up experiment followed treating 150 g of Bedford LT lot 10 soil with and without mixing. The scaled-up processes applied a 3:3:9 (v/v/v) solution resulting in significant decrease in PAH contamination. These findings demonstrate the Peroxy-Acid process as a viable option for the treatment of PAH contaminated soils. Further work is necessary in order to elucidate the mechanisms of this process.
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Peroxy Acid treatment of selected pahs in sediments
International Journal of Environment and Waste Management, 2006Co-Authors: Adeola L Nguessan, Scott N Alderman, Kate Oconnor, Ainiz Abdul Z Rahim, Marianne C NymanAbstract:In an attempt to address some of the disadvantages of the common biotic and abiotic processes used for the degradation of Polycyclic Aromatic Hydrocarbons (PAHs), an alternative strategy utilising a primary chemical oxidative step to be combined with a biological post-treatment step was created. The degradation of α-methylnaphthalene, fluorene, phenanthrene, anthracene, pyrene and benzo(a)pyrene using an Advanced Oxidation Process (AOP) was investigated in a silty–clay sediment type over a 24-hr period. A 5:5:5 ratio of acetic Acid/hydrogen peroxide/DI water, the compounds that form Peroxy-Acids, was used in this study. Gas Chromatography (GC) equipped with a Flame Ionisation Detector (FID) was used to determine the varied rates of degradation of the selected PAHs depending on the set volume ratio of the reagents and the characteristics of the sediment sample. All the six selected PAHs were successfully degraded with the Peroxy-Acid process. Pyrene and fluorene demonstrated lower degradation rates (0.02 and 0.05 hr-1) than α-methylnaphthalene, phenanthrene, anthracene and benzo(a)pyrene (0.16, 0.10, 0.22 and 0.13 hr-1, respectively). All other controls demonstrated minimal degradation over the time-course study.
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remediation of benzo a pyrene in contaminated sediments using Peroxy Acid
Chemosphere, 2004Co-Authors: Adeola L Nguessan, Jeffrey S. Levitt, Marianne C NymanAbstract:Release of benzo(a)pyrene is of an environmental concern due to its toxic nature. To elucidate the degradation of benzo(a)pyrene in lake sediments an advanced oxidation process (AOP) employing Peroxy-Acids as oxidizing agents was investigated. The sediments used in this study were collected from Lake Macatawa (Holland, MI) throughout the eastern basin and ranged in composition from sandy to silty-clay. Laboratory experiments were made by exposing spiked sediment samples to a 1:1:1 v/v/v mixture of hydrogen peroxide/acetic Acid/deionized (DI) water solution. Analytical measurements were performed using gas chromatography equipped with a flame ionization detector. From the AOP experiments, transformation of benzo(a)pyrene was observed in both sediment types over a period of 24-h. The disappearance of the parent compound seemed more rapid with the use of propionic Acid than with acetic Acid, a behavior that is not yet well understood. The organic Acid, DI water, and hydrogen peroxide controls did not demonstrate applicable degradation, suggesting that the disappearance of the parent compound was related to the Peroxy-Acid process.
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optimization of the Peroxy Acid treatment of α methylnaphthalene and benzo a pyrene in sandy and silty clay sediments
Environmental Science & Technology, 2004Co-Authors: Adeola L Nguessan, Todd Carignan, Marianne C NymanAbstract:The majority of polycyclic aromatic hydrocarbons (PAHs) released to the environment come from anthropogenic sources involving the incomplete combustion of organic compounds. Several techniques are available for the degradation of PAHs. Among the abiotic/biotic processes used to degrade PAHs, an alternative strategy utilizing a primary chemical oxidative step to be combined with a biological was created. The degradation of α-methylnaphthalene and benzo[a]pyrene using an advanced oxidation process was optimized over a period of 24 h by varying the ratio of acetic Acid to hydrogen peroxide, the compounds that form Peroxy Acids. The optimization process was performed using sandy and silty-clay sediment types. Gas chromatog raphy equipped with a flame ionization detector was used to determine the varied rates of degradation depending on acetic Acid:hydrogen peroxide ratios and the characteristics of the sediment sample. Reduction of 20−90% of α-methylnaphthalene and benzo[a]pyrene was observed when 2−5 mL of h...
Mauro Freccero - One of the best experts on this subject based on the ideXlab platform.
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Peroxy Acid epoxidation of acyclic allylic alcohols competition between s trans and s cis Peroxy Acid conformers
Journal of Organic Chemistry, 2005Co-Authors: Mauro Freccero, Remo Gandolfi, Mirko Sarziamade, Augusto RastelliAbstract:RB3LYP calculations, reported here, indicate that Peroxy Acid s-cis conformer is more stable than its s-trans counterpart, in agreement with experimental data. Difference in stability is the highest in the gas phase, but it falls considerably on going from the gas phase to moderately polar solvent. In the case of Peroxy formic Acid, the enthalpy (free energy) difference is about 3.4 (2.5) kcal/mol, respectively, in the gas phase but decreases to 1.2 (0.6) kcal/mol in dichloromethane solution. Introduction of an alkyl or aryl substituent on the Peroxy Acid, that is, on passing to Peroxy acetic, Peroxy benzoic (PBA), and m-chloroPeroxy benzoic Acid (MCPBA), adds a further significant (1.0−1.5 kcal/mol) favor to the s-cis isomer. RB3LYP/6-31+G(2d,p) calculations on the epoxidation of 2-propenol with Peroxy formic and Peroxy benzoic Acids, respectively, suggest that the less stable Peroxy Acid s-trans conformer can compete with the more stable s-cis form in epoxidation reaction of these substrates. Transition...
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new paradigms for the Peroxy Acid epoxidation of cc double bonds the role of the Peroxy Acid s trans conformer and of the 1 2 h transfer in the epoxidation of cyclic allylic alcohols
Journal of Organic Chemistry, 2004Co-Authors: Mauro Freccero, Remo Gandolfi, Mirko Sarziamade, Augusto RastelliAbstract:RB3LYP calculations, on reaction of performic Acid with cyclic allylic alcohols, demonstrate that the less stable s-trans conformer of Peroxy Acids can be involved in epoxidations of C=C bonds. Transition structures (TSs) arising from s-trans performic Acid retain some of the well-established characteristics of the TSs of the s-cis isomer such as the perpendicular orientation of the O-H Peroxy Acid bond relative to the C=C bond and a one-step oxirane ring formation. These TSs are very asynchronous but collapse directly (without formation of any intermediate) to the final epoxide-Peroxy Acid complex via a 1,2-H shift. Thus, our findings challenge the traditional mechanism of Peroxy Acid epoxidation of C=C bonds by demonstrating that the involvement of the s-trans isomer opens an alternative one-step reaction channel characterized by a 1,2-H transfer. This novel reaction pathway can even overcome, in the case of the reaction of cyclic allylic alcohols in moderately polar solvents (e.g., in dichloromethane), the classical Bartlett's mechanism that is based on the s-cis Peroxy Acid form and that features a 1,4-H shift. However, the latter mechanism remains strongly favored for the epoxidation of normal alkenes.
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competition between Peroxy Acid oxygens as hydrogen bond acceptors in b3lyp transition structures for epoxidations of allylic alcohols with Peroxyformic Acid
Journal of Organic Chemistry, 1999Co-Authors: Mauro Freccero, Remo Gandolfi, Mirko Sarziamade And, Augusto RastelliAbstract:The transition structures (TSs) for the epoxidation of 2-propen-1-ol and 2-cyclobuten-1-ol with Peroxyformic Acid have been located with the B3LYP method using three basis sets (i.e., 6-31G*, 6-311G**, and 6-311+G**). Syn attacks on these alcohols by Peroxy Acid lead to syn TSs in which hydrogen bonding is operative. The allylic OH group always acts as hydrogen-bond donor while either the carbonyl oxygen or the peroxo oxygens of the Peroxy Acid can play the role of hydrogen-bond acceptors. In the case of propenol, the two syn TSs (O−C−CC dihedral angles: 135.0° and 16.0°, respectively) with the peroxo oxygens involved in hydrogen bonding have free enthalpies comparable with those of their counterparts (O−C−CC dihedral angles: 134.0° and 16.3°, respectively) with hydrogen bonding to carbonyl oxygen. Basis set extension as well as electrostatic solvation effects favor the former TSs over the latter ones. In the case of cyclobutenol the syn TS (O−C−CC dihedral angle = 124.2°) with hydrogen bonding to perox...
Remo Gandolfi - One of the best experts on this subject based on the ideXlab platform.
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Peroxy Acid epoxidation of acyclic allylic alcohols competition between s trans and s cis Peroxy Acid conformers
Journal of Organic Chemistry, 2005Co-Authors: Mauro Freccero, Remo Gandolfi, Mirko Sarziamade, Augusto RastelliAbstract:RB3LYP calculations, reported here, indicate that Peroxy Acid s-cis conformer is more stable than its s-trans counterpart, in agreement with experimental data. Difference in stability is the highest in the gas phase, but it falls considerably on going from the gas phase to moderately polar solvent. In the case of Peroxy formic Acid, the enthalpy (free energy) difference is about 3.4 (2.5) kcal/mol, respectively, in the gas phase but decreases to 1.2 (0.6) kcal/mol in dichloromethane solution. Introduction of an alkyl or aryl substituent on the Peroxy Acid, that is, on passing to Peroxy acetic, Peroxy benzoic (PBA), and m-chloroPeroxy benzoic Acid (MCPBA), adds a further significant (1.0−1.5 kcal/mol) favor to the s-cis isomer. RB3LYP/6-31+G(2d,p) calculations on the epoxidation of 2-propenol with Peroxy formic and Peroxy benzoic Acids, respectively, suggest that the less stable Peroxy Acid s-trans conformer can compete with the more stable s-cis form in epoxidation reaction of these substrates. Transition...
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new paradigms for the Peroxy Acid epoxidation of cc double bonds the role of the Peroxy Acid s trans conformer and of the 1 2 h transfer in the epoxidation of cyclic allylic alcohols
Journal of Organic Chemistry, 2004Co-Authors: Mauro Freccero, Remo Gandolfi, Mirko Sarziamade, Augusto RastelliAbstract:RB3LYP calculations, on reaction of performic Acid with cyclic allylic alcohols, demonstrate that the less stable s-trans conformer of Peroxy Acids can be involved in epoxidations of C=C bonds. Transition structures (TSs) arising from s-trans performic Acid retain some of the well-established characteristics of the TSs of the s-cis isomer such as the perpendicular orientation of the O-H Peroxy Acid bond relative to the C=C bond and a one-step oxirane ring formation. These TSs are very asynchronous but collapse directly (without formation of any intermediate) to the final epoxide-Peroxy Acid complex via a 1,2-H shift. Thus, our findings challenge the traditional mechanism of Peroxy Acid epoxidation of C=C bonds by demonstrating that the involvement of the s-trans isomer opens an alternative one-step reaction channel characterized by a 1,2-H transfer. This novel reaction pathway can even overcome, in the case of the reaction of cyclic allylic alcohols in moderately polar solvents (e.g., in dichloromethane), the classical Bartlett's mechanism that is based on the s-cis Peroxy Acid form and that features a 1,4-H shift. However, the latter mechanism remains strongly favored for the epoxidation of normal alkenes.
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competition between Peroxy Acid oxygens as hydrogen bond acceptors in b3lyp transition structures for epoxidations of allylic alcohols with Peroxyformic Acid
Journal of Organic Chemistry, 1999Co-Authors: Mauro Freccero, Remo Gandolfi, Mirko Sarziamade And, Augusto RastelliAbstract:The transition structures (TSs) for the epoxidation of 2-propen-1-ol and 2-cyclobuten-1-ol with Peroxyformic Acid have been located with the B3LYP method using three basis sets (i.e., 6-31G*, 6-311G**, and 6-311+G**). Syn attacks on these alcohols by Peroxy Acid lead to syn TSs in which hydrogen bonding is operative. The allylic OH group always acts as hydrogen-bond donor while either the carbonyl oxygen or the peroxo oxygens of the Peroxy Acid can play the role of hydrogen-bond acceptors. In the case of propenol, the two syn TSs (O−C−CC dihedral angles: 135.0° and 16.0°, respectively) with the peroxo oxygens involved in hydrogen bonding have free enthalpies comparable with those of their counterparts (O−C−CC dihedral angles: 134.0° and 16.3°, respectively) with hydrogen bonding to carbonyl oxygen. Basis set extension as well as electrostatic solvation effects favor the former TSs over the latter ones. In the case of cyclobutenol the syn TS (O−C−CC dihedral angle = 124.2°) with hydrogen bonding to perox...
Adeola L Nguessan - One of the best experts on this subject based on the ideXlab platform.
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effective treatment of pah contaminated superfund site soil with the Peroxy Acid process
Journal of Hazardous Materials, 2007Co-Authors: Scott N Alderman, Adeola L Nguessan, Marianne C NymanAbstract:Peroxy-organic Acids are formed by the chemical reaction between organic Acids and hydrogen peroxide. The Peroxy-Acid process was applied to two Superfund site soils provided by the U.S. Environmental Protection Agency (EPA). Initial small-scale experiments applied ratios of 3:5:7 (v/v/v) or 3:3:9 (v/v/v) hydrogen peroxide:acetic Acid:deionized (DI) water solution to 5 g of Superfund site soil. The experiment using 3:5:7 (v/v/v) ratio resulted in an almost complete degradation of the 14 EPA regulated polycyclic aromatic hydrocarbons (PAHs) in Bedford LT soil during a 24-h reaction period, while the 3:3:9 (v/v/v) ratio resulted in no applicable degradation in Bedford LT lot 10 soil over the same reaction period. Specific Superfund site soil characteristics (e.g., pH, total organic carbon content and particle size distribution) were found to play an important role in the availability of the PAHs and the efficiency of the transformation during the Peroxy-Acid process. A scaled-up experiment followed treating 150 g of Bedford LT lot 10 soil with and without mixing. The scaled-up processes applied a 3:3:9 (v/v/v) solution resulting in significant decrease in PAH contamination. These findings demonstrate the Peroxy-Acid process as a viable option for the treatment of PAH contaminated soils. Further work is necessary in order to elucidate the mechanisms of this process.
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Peroxy Acid treatment of selected pahs in sediments
International Journal of Environment and Waste Management, 2006Co-Authors: Adeola L Nguessan, Scott N Alderman, Kate Oconnor, Ainiz Abdul Z Rahim, Marianne C NymanAbstract:In an attempt to address some of the disadvantages of the common biotic and abiotic processes used for the degradation of Polycyclic Aromatic Hydrocarbons (PAHs), an alternative strategy utilising a primary chemical oxidative step to be combined with a biological post-treatment step was created. The degradation of α-methylnaphthalene, fluorene, phenanthrene, anthracene, pyrene and benzo(a)pyrene using an Advanced Oxidation Process (AOP) was investigated in a silty–clay sediment type over a 24-hr period. A 5:5:5 ratio of acetic Acid/hydrogen peroxide/DI water, the compounds that form Peroxy-Acids, was used in this study. Gas Chromatography (GC) equipped with a Flame Ionisation Detector (FID) was used to determine the varied rates of degradation of the selected PAHs depending on the set volume ratio of the reagents and the characteristics of the sediment sample. All the six selected PAHs were successfully degraded with the Peroxy-Acid process. Pyrene and fluorene demonstrated lower degradation rates (0.02 and 0.05 hr-1) than α-methylnaphthalene, phenanthrene, anthracene and benzo(a)pyrene (0.16, 0.10, 0.22 and 0.13 hr-1, respectively). All other controls demonstrated minimal degradation over the time-course study.
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remediation of benzo a pyrene in contaminated sediments using Peroxy Acid
Chemosphere, 2004Co-Authors: Adeola L Nguessan, Jeffrey S. Levitt, Marianne C NymanAbstract:Release of benzo(a)pyrene is of an environmental concern due to its toxic nature. To elucidate the degradation of benzo(a)pyrene in lake sediments an advanced oxidation process (AOP) employing Peroxy-Acids as oxidizing agents was investigated. The sediments used in this study were collected from Lake Macatawa (Holland, MI) throughout the eastern basin and ranged in composition from sandy to silty-clay. Laboratory experiments were made by exposing spiked sediment samples to a 1:1:1 v/v/v mixture of hydrogen peroxide/acetic Acid/deionized (DI) water solution. Analytical measurements were performed using gas chromatography equipped with a flame ionization detector. From the AOP experiments, transformation of benzo(a)pyrene was observed in both sediment types over a period of 24-h. The disappearance of the parent compound seemed more rapid with the use of propionic Acid than with acetic Acid, a behavior that is not yet well understood. The organic Acid, DI water, and hydrogen peroxide controls did not demonstrate applicable degradation, suggesting that the disappearance of the parent compound was related to the Peroxy-Acid process.
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optimization of the Peroxy Acid treatment of α methylnaphthalene and benzo a pyrene in sandy and silty clay sediments
Environmental Science & Technology, 2004Co-Authors: Adeola L Nguessan, Todd Carignan, Marianne C NymanAbstract:The majority of polycyclic aromatic hydrocarbons (PAHs) released to the environment come from anthropogenic sources involving the incomplete combustion of organic compounds. Several techniques are available for the degradation of PAHs. Among the abiotic/biotic processes used to degrade PAHs, an alternative strategy utilizing a primary chemical oxidative step to be combined with a biological was created. The degradation of α-methylnaphthalene and benzo[a]pyrene using an advanced oxidation process was optimized over a period of 24 h by varying the ratio of acetic Acid to hydrogen peroxide, the compounds that form Peroxy Acids. The optimization process was performed using sandy and silty-clay sediment types. Gas chromatog raphy equipped with a flame ionization detector was used to determine the varied rates of degradation depending on acetic Acid:hydrogen peroxide ratios and the characteristics of the sediment sample. Reduction of 20−90% of α-methylnaphthalene and benzo[a]pyrene was observed when 2−5 mL of h...