Hydroxylamine Group Research Articles

ChemInform Abstract: Synthesis and Characterization of Encapsulated Cobalt(III) Hydroxylamine Complexes.

AbstractOn treatment of the cage complexes (I) with H2O2 in basic solution, up to three coordinated N sites are oxidized to hydroxylamine groups.

Formation of 4,5-dihydro-1,2,4-triazoles during rearrangement of O-acetyl derivatives of 1,2-hydroxylaminohydrazones and thiosemicarbazones

Acylation of phenylhydrazone, semicarbazone, and thiosemicarbazones of 1,2-hydroxyl-amino-ketones containing a hydroxylamine group at the tertiary carbon atom, by acetic anhydride, leads to products of O-acylation at the hydroxylamine group, which in alkali medium rearrange to form 4,5-dihydro-1,2,4-triazoles.

Coordination compounds of Cu(II) with the nitroxyl radical 2-acetyl-2,5,5-trimethyl-4-phenyl-3-imidazoline-3-oxide-1-oxyl thiosemicarbazone and its 1-hydroxy derivative

1. During the formation of complexes of Cu(II) with 2-acety1-2,5,5-trimethyl-4-phenyl-3-imidazoline-3-oxide-1-oxyl thiosemicarbazone, which has a donor functional group adjacent to the radical center, in methanol, chloroform, CH2Cl2, or acetone, the nitroxyl group of the ligand is reduced to the hydroxylamine. In alkaline solution, on the other hand, in the presence of Cu(II) salts the hydroxylamine group of 2-acety1-2,5,5-trimethy1-4-phenyl-3-imidazoline-1-hydroxy-3-oxide thiosemicarbazone is converted into the nitroxyl. 2. The coordination compound with the nitroxyl radical is diamagnetic, apparently owing to strong antiferromagnetic interaction between the unpaired electrons of the paramagnetic centers arising as a result of coordination of the group by the Cu(II) ion.

Kinetics of the reduction of nitro to hydroxylamine groups by dithionite in a cobalt(II) cryptand complex. X-ray analysis of [1,8-bis(hydroxylamino)-3,6,10,13,16,19-hexaazabicyclo[6.6.6]eicosane]cobalt(III) chloride tetrahydrate

Etude cinetique de la reaction de reduction et etude cristallographique du compose du titre forme. Cristallisation dans le groupe P2 1 /n avec a=11,212, b=18,327 et c=13,713 A, β=103,24°, Z=4. Affinement jusqu'a R=0,034. Symetrie D 3 du cation si l'on ne tient pas compte des parties NH 2 OH

Electrochemical reduction of 2,2'-dinitrophenyl ether and 2,2'-dinitrodiphenylamine at mercury cathodes

2,2'-Dinitrophenyl ether (I) is reduced at less negative potentials than 2,2'-dinitrodiphenylamine (II); the respective mechanism of their reduction differ essentially. (I) is electrolytically reduced in a single wave with an uptake of eight electrons per molecule, giving rise to a bishydroxylamine intermediate which undergoes an intramolecular disproportionation. The resulting 2-nitroso-2'-amino-diphenyl ether undergoes a chemical follow-up reaction leading on the one hand to dibenzo-(b,e)-(1,4,5)-oxadiazepine, on the other hand to a diphenylamine product (resulting by a chemical rearrangement) which reacts with reductants present in the solution and yields dihydrophenazine. It is merely by chance that in the electrolytical reduction of II dihydrophenazine also results in addition to other products. 2,2'-dinitrodiphenylamine (II) enables here, however, a partial electrolytical reduction in which 2-amino-2'-nitrophenylamine is formed in a single 6-electron wave. In the following, more negative wave, is clearly separated only in alkaline media, the other nitro group reduces with an uptake of 4 electrons to an intermediate which eliminates the hydroxylamine group with the corresponding electron pair. The subsequent chemical reaction leads to dihydrophenazine. This substance is the reduced form of an chemicaly and electrochemically reversible system, this system participates in the chemical reactions of reaction intermediates. Its regeneration readily proceeds at potentials more positive than the reduction potential of II. Phenazine is oxidized in the catholyte by the hydroxylamine set free to phenazine N-oxide. Nitrogen is thus eliminated in its elemental form via hydroxylamine from the substrate molecule.

Cell death and free radicals: A mechanism for hydroxyurea teratogenesis

Hydroxyurea is a drug which causes birth defects in a variety of animals. Its pharmacologic actions include rapid killing of proliferating cells and profound inhibition of the synthesis of DNA. The mechanism whereby hydroxyurea produces teratogenesis is unresolved although it is related to the pharmacologic actions. Careful reading of the scientific literature discloses several putative mechanisms for the teratogenic action of hydroxyurea, which account for the inhibited synthesis of DNA, but do not explain the rapid onset of cell death. This paper presents a hypothesis that hydroxyurea causes rapid cell death through the initiation of uncontrolled free radical chain reactions. In vitro biochemical experiments have demonstrated the ability of compounds containing a hydroxylamine group (such as hydroxyurea) to form H 2O 2 and intermediate free radicals in biological fluids. Free radicals propagate themselves through chain reactions and can react swiftly and indiscriminately with the macromolecules of cells. Radical reactions are able to devastate cellular metabolism quickly by inactivating enzymes, cross-linking DNA, and altering membrane functions through lipid auto-oxidation. Preliminary experiments utilizing an antioxidant to counteract the free radical effects appear to support the hypothesis that the rapid cell death is caused by aberrant free radical reactions.

A spectrophotometric and polarographic investigation of three new cyclohexene-substituted benzodiazepines

Three recently introduced benzodiazepine derivatives, tetrazepam ( I), nortetrazepam ( II) and menitrazepam ( III) have been subjected to spectral and polarographic investigation. From the ultraviolet spectral data their p K a-values have been determined: 4.28 ( I), 4.3 ( II) and 3.5 ( III). From the polarographic measurements it can be concluded that in I and II the 4,5 CN double bond is reduced with 2 electrons. For the first time for the benzodiazepine series it has been observed that in slightly alkaline solutions this process takes place in two separate 1-electron steps. In III, first the aromatic nitro group is reduced to a hydroxylamine group, then at more negative potentials the CN double bond is also reduced; its reduction wave mostly coalesces with that for the 6-electron reduction of the nitro group to an amino group. A differential pulse polarographic method is presented, for the determination of I, II, III at concentrations as low as 10 −7 M.

Alstonia scholaris: the structure of the indole alkaloid nareline (author's transl)

Alstonia scholaris: The structure of the indole alkaloid narelineBesides the known akuammidine, picralinal, picrinine and pseudoakuammigine a new indole alkaloid called nareline (M=352) was isolated from Alstonia scholaris R. BR., which belongs to the plant family of Apocynaceae. Its structure 2 was deduced by single crystal X‐ray diffraction. 2 represents the absolute configuration. The spectroscopic data of 2 and its derivatives (Scheme 1) as well as their chemical behavior support this structure. In biogenetic sense nareline is related to the bases akuammiline (4) and picraline (5) (Scheme 2). In contrast to those the C‐atom 5 is exocyclic and represents an aldehyde group which forms together with the oxygen atom of the N (4)‐hydroxylamine group a cyclic half acetale. ‐ By oxidation (CrO3/CH3COOH) of 2 the oxindol derivative 19 (oxonareline) is formed which contains a cyclic acetal as a partial structure element (Scheme 4).

An ultraviolet spectral and polarographic study of nitrofurantoin, a urinary-tract antibiotic.

Nitrofurantoin, a urinary-tract antibiotic, exists in four different forms over the pH range 0–14, corresponding to the divalent cation H3A2+, the monovalent cation H2A+, the neutral species HA and the monovalent anion A–, as investigated by means of ultraviolet spectrophotometry. The compound is polarographically reducible over the whole pH range, the nitro group being reduced to the hydroxylamine group in a 4e process and subsequently the amine being formed in a 2e process at a pH value below 5. The CN—N linkage is reduced by a mechanism involving reductive fission of the N—N bond. The best defined differential pulse polarographic waves for the reduction of the nitro group to hydroxylamine are obtained in the pH range 6–12.Experiments involving spiking of urine have been carried out and a method is suggested for the determination of nitrofurantoin in urine over the concentration range 2–24 µg ml–1.

Polarographic determination of chloramphenicol

The electroreduction of chloramphenicol has been studied by polarography, cyclic voltammetry, chronopotentiometry and coulometry. The experimental results lead to the conclusion that the drug undergoes a slow 2-electron reduction of the nitro group which is followed by a fast 2-electron reduction to hydroxylamine. At more negative potentials the hydroxylamine group is further reduced to the amine. In acetate buffer pH 4.7 with 0.003 % decylamine present, the drug produces a very well-defined, diffusion-controlled 4-electron polarographic wave. The current is proportional to the concentration and permits the drug to be determined by polarography in the concentration range 0.3–600 μg ml -1. A rapid polarographic method for the determination of chloramphenicol in milk is proposed.

Identification of the aromatic hydroxylamine group by mass spectrometry

AbstractThe mass spectra of aromatic hydroxylamines are diagnostic; [M], [M – 2], [M – 16] and, in most instances, [M – 17] ions are observed.

Urease Catalysis: III. Stoichiometry, Kinetics, and Inhibitory Properties of a Third Substrate: Dihydroxyurea

Abstract Urease catalyzes the degradation of dihydroxyurea (HOHN-CO-NHOH) in aqueous solution. It was shown that the decline in dihydroxyurea was paralleled by the appropriate stoichiometric appearance of hydroxylamine and carbon dioxide, thus eliminating adsorption and contaminant substrates as the responsible factors. The reaction was not elicited by equivalent concentrations of bovine serum albumin, and the dihydroxyurea/urea specific activity ratio was maintained over a 70-fold range of urease purity. The catalysis is thus urease-specific and not due to proteins in general, nor to another enzyme contaminating urease preparations. In Tris-maleate buffers the pH activity curves for dihydroxyurea, (mono)hydroxyurea, and urea all had maxima at pH 7.0, with progressive narrowing of the activity range as hydroxylamine groups replaced amine groups in the substrates. Despite a high Km = 12.5 mm, dihydroxyurea, which has no primary amide bond, was hydrolyzed more rapidly than (mono)hydroxyurea, which has. Like the latter compound, dihydroxyurea also produced marked inhibition of urease. The inhibition was less powerful, however, than that generated by hydroxyurea and the aliphatic hydroxamates, and was kinetically reversible and noncompetitive with Ki = 0.14 mm.

Sur un principe de colorimétrie en milieu non aqueux—II: Emploi du bromure de p-nitrophénacyle pour l'identification et le dosage des acides carboxyliques

Supplementing the identification tests in non-aqueous medium for hydroxyl, carbonyl and primary amine groups, already described ( Talanta 1960, 5, 216) it is possible to characterise carboxylic acids in the form of the p-nitrophenacyl esters. These esters, without the necessity for extraction or of the elimination of excess reagent, develop a colour with dimethylamine when treated in mixture with acetonitrile and dimethylsulphoxide. Tests can be carried out on amounts of the order of 0.01 mg.

Polarography of Some Aromatic Nitro and Carbonyl Compounds

The polarographic reduction of the nitro and carbonyl groups in 2‐nitro‐fluorenone, 2,7‐dinitrofluorenone, and 2,5‐dinitrofluorenone has been studied in buffered solutions over a pH range of about 1–13. To aid in interpreting the electrode reactions, additional polarographic studies were made with several compounds containing only the nitro or carbonyl group. These compounds were fluorenone, 4‐nitrobiphenyl, 4,4′‐dinitrobiphenyl, 2.4′‐dinitrobiphenyl, 2,5‐dinitrofluorene, and 2‐aminofluorenone, and the polarography was carried out under the same solution conditions. The number of electrons involved in the reduction steps of several of these compounds was measured using the controlled cathode potential technique. It was found that the characteristic double waves of the carbonyl group in fluorenone are merged into a single two‐electron wave in the dinitrofluorenones. This effect is apparently a general one, caused by the decrease in stability of the intermediate free radical brought about by the hydroxylamine groups in the aromatic nucleus.

Reactions involving the amide and carboxyl groups of tobacco mosaic virus (TMV) protein

Treatment of TMV with 3 M hydroxylamine at pH 7.5 leads to a substituted product containing 21 bound hydroxylamine groups. Protein samples obtained by disruption of the virus in various ways participate in the reaction with hydroxylamine to a much smaller extent. The claim that the treatment of TMV with hydroxylamine at 60° leads to specific cleavage of a single peptide bond and exposes a reactive proline imino group could not be substantiated. Two approaches to the estimation of asparagine and glutamine residues in TMV-protein have been studied. The esterification of the free carboxyl groups and reduction of the protein ester was found to leave the amino acid amides intact. Subsequent hydrolysis of the protein derivative and estimation of the two dicarboxylic acids present provided data on the number of asparagine and glutamine residues originally present. The data indicate that TMV-protein of molecular weight 18,270 contains 21 amide residues per mole and that of these 12 ± 1 belong to asparagine and 9 ± 1 to glutamine. The second approach studied was the hydrazinolysis technique involving the differentiation of the resulting mono- and di-hydrazides of the dicarboxylic amino acids. This method, however, seems to be not useful for quantitative purposes because of the need for large correction factors. The data for the asparagine and glutamine content exceed by a large margin the amount of amide N present in the protein and are not in accord with the values from the reduction experiments.