- Conversion of anilines into azobenzenes in acetic acid with perborate and Mo(VI): correlation of reactivities
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Azobenzenes are extensively used to dye textiles and leather and by tuning the substituent in the ring, vivid colours are obtained. Here, we report preparation of a large number of azobenzenes in good yield from commercially available anilines using sodium perborate (SPB) and catalytic amount of Na2MoO4 under mild conditions. Glacial acetic acid is the solvent of choice and the aniline to azobenzene conversion is zero, first and first orders with respect to SPB, Na2MoO4 and aniline, respectively. Based on the kinetic orders, UV–visible spectra and cyclic voltammograms, the conversion mechanism has been suggested. The reaction rates of about 50 anilines at 20–50?°C and their energy and entropy of activation conform to the isokinetic or Exner relationship and compensation effect, respectively. However, the reaction rates, deduced by the so far adopted method, fail to comply with the Hammett correlation. The specific reaction rates of molecular anilines, obtained through a modified calculation, conform to the Hammett relationship. Thus, this work presents a convenient inexpensive non-hazardous method of preparation of a larger number of azobenzenes, and shows the requirement of modification in obtaining the true reaction rates of anilines in acetic acid and the validity of Hammett relationship in the conversion process, indicating operation of a common mechanism.
- Karunakaran,Venkataramanan
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p. 375 - 385
(2019/02/14)
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- Oxidation of secondary amines by molecular oxygen and cyclohexanone monooxygenase
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Cyclohexanone monooxygenase from Acinetobacter calcoaceticus catalyzed the oxidation of tertiary and secondary amines to N-oxides and nitrones, respectively. The formation of a hydroxylamine intermediate was involved with secondary amines as starting substrates.
- Colonna, Stefano,Pironti, Vincenza,Carrea, Giacomo,Pasta, Piero,Zambianchi, Francesca
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p. 569 - 575
(2007/10/03)
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- Oxidation of amines catalyzed by cyclohexanone monooxygenase
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Cyclohexanone monooxygenase catalyzed the oxidation of tertiary, secondary and hydroxylamines to N-oxides, hydroxylamines and nitrones respectively.
- Colonna, Stefano,Pironti, Vincenza,Pasta, Piero,Zambianchi, Francesca
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p. 869 - 871
(2007/10/03)
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- Photo-induced DNA-cleaving agents
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The present invention discloses a photo-induced DNA-cleaving agent composition comprises N-aryl-N-(alkyl or arylalkyl)hydroxylamine having the following formula: STR1 wherein R is C1 -C6 alkyl, phenyl, C1 -C6 alkoxy, phenoxy, C1 -C6 alkoxycarbonyl, halogen or halo(C1 -C6 alkyl)wherein R1 is hydrogen, C1 -C6 alkyl, phenyl, C1 -C6 alkoxy, C1 -C6 alkoxycarbonyl, halogen or halo(C1 -C6 alkyl); R2 is hydrogen; R3 is hydrogen or phenyl; R4 is hydrogen, phenyl, hydroxylphenyl, methoxyphenyl, dimethoxyphenyl, dimethylaminophenyl or naphthyl. The present N-aryl-N-(alkyl or arylalkyl)hydroxylamine is stable in dark, but it can react with O2 to form HO. radicals under irradiation of UV light for a period of 2-3 hours. The HO. radicals then react with DNA to accomplish cleavage of DNA.
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- Oxidation of Amines by a 4a-Hydroperoxyflavin
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Kinetic and product studies have been carried out for the reaction of 12 tertiary amines, secondary amines, and secondary hydroxylamines with the 4a-hydroperoxide of N5-ethyl-3-methyllumiflavin (4a-FlEtOOH).All reactions were found to be first order in 4a-FlEtOOH and amine in t-BuOH solvent.Transfer from t-BuOH to the aprotic solvent dioxane decreases the second-order rate constant by ca. threefold, but does not change the kinetic order in reactants (i.e., no external proton source is required).The reactions with the secondary and tertiary amines are quantitative, yielding secondary hydroxylamines and tertiary amine oxides along with the flavin pseudobase (4a-FlEtOH).Secondary hydroxylamines yield with 4a-FlEtOOH nitrones and 4a-FlEtOH.The free radical trap 2,6-di-tert-butyl-4-methylphenol does not influence the rate constants or product yields.This finding, along with the observation that rate constants are not related to the stability of cation radicals derived from amine, establishes that free radical processes are not involved in the N-oxidation reactions.The N-oxidation reactions are best explained as occurring through nucleophilic attack of amine nitrogen upon the terminal oxygen of the 4a-FlEtOOH molecule with back donation of the hydroperoxy hydrogen to the internal peroxy oxygen.Comparison of the second-order rate constants ( on the basis of the amine pKa's in H2O) provides the nucleophilic order secondary hydroxylamines > tertiary amines > secondary amines.The disappearance of 4a-FlEtOOH from solution in the presence of primery amines is much slower than with secondary amines and the reaction does not follow a simple rate law nor is 4a-FlEtOH a major product.In t-BuOH the spontaneous first-order rate constant for decomposition of 4a-FlEtOOH exceeds that for the decomposition of H2O2 by more than 400-fold while the second-order rate constant for N-oxidation of N,N-dimethylbenzylamine by 4a-FlEtOOH exceeds that for N-oxidation by H2O2 by 36000-fold (and N-oxidation by t-BuOOH by > 400000).These results are discussed in terms of the involvement of 4a-hydroperoxyflavin cofactor in the metabolism of amines by the hepatic flavoprotein microsomal oxidase.
- Ball, Sheldon,Bruice, Thomas C.
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p. 6498 - 6503
(2007/10/02)
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