Science and Technology Production
Article
Authorship
Date
2003
Publishing House and Editing Place
ROYAL SOC CHEMISTRY
Magazine
Photochemical and Photobiological Sciences
(pp. 882-887)
ROYAL SOC CHEMISTRY
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The oxidation kinetics and mechanism of the phenolic derivatives of α,α,α-trifluorotoluene, 2-trifluoromethylphenol, 3-trifluoromethylphenol (3-TFMP), 4-trifluoromethylphenol and 3,5-bis(trifluoromethyl)phenol, mediated by singlet molecular oxygen, O2(1∆g), and hydrogen phosphate radicals were studied, employing time-resolved O2(1∆g) phosphorescence detection, polarographic determination of dissolved oxygen and flash photolysis. All the substrates are highly photo-...
The oxidation kinetics and mechanism of the phenolic derivatives of α,α,α-trifluorotoluene, 2-trifluoromethylphenol, 3-trifluoromethylphenol (3-TFMP), 4-trifluoromethylphenol and 3,5-bis(trifluoromethyl)phenol, mediated by singlet molecular oxygen, O2(1∆g), and hydrogen phosphate radicals were studied, employing time-resolved O2(1∆g) phosphorescence detection, polarographic determination of dissolved oxygen and flash photolysis. All the substrates are highly photo-oxidizable through a O2(1∆g)-mediated mechanism. The phenols show overall quenching constants for O2(1∆g) of the order of 106 M1 s1 in D2O, while the values for the phenoxide ions in water range from 1.2 × 108 α,α,α-trifluorotoluene, 2-trifluoromethylphenol, 3-trifluoromethylphenol (3-TFMP), 4-trifluoromethylphenol and 3,5-bis(trifluoromethyl)phenol, mediated by singlet molecular oxygen, O2(1∆g), and hydrogen phosphate radicals were studied, employing time-resolved O2(1∆g) phosphorescence detection, polarographic determination of dissolved oxygen and flash photolysis. All the substrates are highly photo-oxidizable through a O2(1∆g)-mediated mechanism. The phenols show overall quenching constants for O2(1∆g) of the order of 106 M1 s1 in D2O, while the values for the phenoxide ions in water range from 1.2 × 108 fluoromethylphenol (3-TFMP), 4-trifluoromethylphenol and 3,5-bis(trifluoromethyl)phenol, mediated by singlet molecular oxygen, O2(1∆g), and hydrogen phosphate radicals were studied, employing time-resolved O2(1∆g) phosphorescence detection, polarographic determination of dissolved oxygen and flash photolysis. All the substrates are highly photo-oxidizable through a O2(1∆g)-mediated mechanism. The phenols show overall quenching constants for O2(1∆g) of the order of 106 M1 s1 in D2O, while the values for the phenoxide ions in water range from 1.2 × 108 2(1∆g), and hydrogen phosphate radicals were studied, employing time-resolved O2(1∆g) phosphorescence detection, polarographic determination of dissolved oxygen and flash photolysis. All the substrates are highly photo-oxidizable through a O2(1∆g)-mediated mechanism. The phenols show overall quenching constants for O2(1∆g) of the order of 106 M1 s1 in D2O, while the values for the phenoxide ions in water range from 1.2 × 108 flash photolysis. All the substrates are highly photo-oxidizable through a O2(1∆g)-mediated mechanism. The phenols show overall quenching constants for O2(1∆g) of the order of 106 M1 s1 in D2O, while the values for the phenoxide ions in water range from 1.2 × 108 2(1∆g)-mediated mechanism. The phenols show overall quenching constants for O2(1∆g) of the order of 106 M1 s1 in D2O, while the values for the phenoxide ions in water range from 1.2 × 1082(1∆g) of the order of 106 M1 s1 in D2O, while the values for the phenoxide ions in water range from 1.2 × 108 to 3.6 × 108 M1 s1. The effects of the pH and polarity of the medium on the kinetics of the photo-oxidative process suggest a charge-transfer mechanism. 2-Trifluoromethyl-1,4-benzoquinone is suspected to be the main photooxidation product for the substrate 3-TFMP. The absolute rate constants for the reactions of HPO4 8 M1 s1. The effects of the pH and polarity of the medium on the kinetics of the photo-oxidative process suggest a charge-transfer mechanism. 2-Trifluoromethyl-1,4-benzoquinone is suspected to be the main photooxidation product for the substrate 3-TFMP. The absolute rate constants for the reactions of HPO4 fluoromethyl-1,4-benzoquinone is suspected to be the main photooxidation product for the substrate 3-TFMP. The absolute rate constants for the reactions of HPO44 with the substrates range from 4 × 108 to 1 × 109 M1 s1. The 3-trifluoromethylphenoxyl radical was observed as the organic intermediate formed after reaction of 3-TFMP with HPO4 with the substrates range from 4 × 108 to 1 × 109 M1 s1. The 3-trifluoromethylphenoxyl radical was observed as the organic intermediate formed after reaction of 3-TFMP with HPO4 8 to 1 × 109 M1 s1. The 3-trifluoromethylphenoxyl radical was observed as the organic intermediate formed after reaction of 3-TFMP with HPO44 , yielding 2,2-bis(fluorohydroxymethyl)biphenyl-4,4- diol as the end product. The observed results indicate that singlet molecular oxygen and hydrogen phosphate radicals not only react at different rates with the phenols of α,α,α-trifluorotoluene, but the reactions also proceed through different reaction channels. , yielding 2,2-bis(fluorohydroxymethyl)biphenyl-4,4- diol as the end product. The observed results indicate that singlet molecular oxygen and hydrogen phosphate radicals not only react at different rates with the phenols of α,α,α-trifluorotoluene, but the reactions also proceed through different reaction channels. fferent rates with the phenols of α,α,α-trifluorotoluene, but the reactions also proceed through different reaction channels.fferent reaction channels.
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Key Words
singlet molecular oxygenphosphate radicals,,-trifluorotoluene