High performance liquid chromatography (HPLC), ultraviolet spectroscopy (UV), and total organic carbon (TOC) analyses show that caffeine is quickly and completely degraded underthe oxidative conditions of the UV/H2O2,TiO2/ UV, and Fenton systems but that the organic carbon content of the solution decreases much more slowly. Continuous on-line and real-time monitoring by electrospray ionization mass (ESI-MS) and tandem mass spectrometric experiments (ESI-MS/MS) as well as high accuracy MS measurements and gas chromatography-mass spectrometry analysis show that caffeine is first oxidized to N-dimethylparabanic acid likely via initial OH insertion to the C4=C8 caffeine double bond. A second degradation intermediate, di(N-hidroxymethyl)parabanic acid, has been identified by ESI-MS and characterized by ESI-MS/MS and high accuracy mass measurements. This polar and likely relatively unstable compound, which is not detected by off-line GC-MS analysis, is likely formed via further oxidation of N-dimethylparabanic acid at both of its N-methyl groups and constitutes an unprecedented intermediate in the degradation of caffeine.

The degradation of tetracycline (1) by ozone in aqueous solution was investigated. High performance liquid chromatography (HPLC), UV-visible spectroscopy (UV-Vis), and total organic carbon (TOC) analyses revealed that although tetracycline was quickly consumed under this oxidative condition, it did not mineralize at all. Continuous monitoring by electrospray ionization mass spectrometry in the positive ion mode, ESI(ϩ)-MS, revealed that tetracycline (1), detected in its protonated form ([1 ϩ H] ϩ ) of m/z 445, reacted to yield almost exclusively two unprecedented oxidation products (2 and 3) via a net insertion of one and two oxygen atoms, respectively. Compound 2, suggested to be formed via an initial 1,3-dipolar cycloaddition of ozone at the C11a-C12 double-bond of 1, and Compound 3, proposed to be produced via a subsequent ozone attack at the C2-C3 double-bond of 2, were detected in their protonated forms in the ESI(ϩ)-MS, i.e.,

In this work the surface of activated carbon was chemically modified in order to introduce O, S and N containing groups. The activated carbon surface was selectively oxidized with concentrated HNO 3 under controlled conditions. Characterization by thermogravimetric analyses, infrared spectroscopy and NaOH titration suggested the formation of mainly -COOH and small amounts of -OH groups, with concentration of approximately 4.10 21 groups/g of carbon. These -COOH functionalized carbons showed high adsorption capacity for metal cations in aqueous solution in the following order: Pb ]. These -COOH surf groups can be reacted with SOCl 2 to produce a surface acylchloride group, -COCl. This surface -COCl group proved to be a very reactive and versatile intermediate for the grafting of different S and N containing molecules onto the carbon surface, such as 1,2-ethaneditiol (EDT-, HSCH 2 CH 2 SH) 1,7-dimercapto-4-thioheptane (DMTH-HSCH 2 CH 2 CH 2 SCH 2 CH 2 CH 2 SH) or 1,2-ethylenediamine (EDA-NH 2 CH 2 CH 2 NH 2 ) and triethyltetraamine, TEA (H 2 NCH 2 CH 2 NHCH 2 CH 2 NHCH 2 CH 2 NH 2 ). The characterization of these materials was carried out by TG, IR and TPDMS (Temperature Programmed Decomposition Mass Spectrometry) experiments suggesting the formation of thioesther and amide surface groups, i.e. -COSR and -CONHR, with yields of approximately 50 and 75% for the reaction with DME and EDA, respectively. Preliminary adsorption experiments showed that these materials can efficiently remove metals such as Pb +2 , Cu +2 and Ni +2 from aqueous medium.

The degradation of the dye indigo carmine in aqueous solution induced by two oxidative processes (H(2)O(2)/iodide and O(3)) was investigated. The reactions were monitored by electrospray ionization mass spectrometry in the negative ion mode, ESI(-)-MS, and the intermediates and oxidation products characterized by ESI(-)-MS/MS. Both oxidative systems showed to be highly efficient in removing the color of the dye aqueous solutions. In the ESI(-)-MS of the indigo carmine solution treated with H(2)O(2) and H(2)O(2)/iodide, the presence of the ions of m/z 210 (indigo carmine in its anionic form, 1), 216, 226, 235, and 244 was noticeable. The anion of m/z 235 was proposed to be the unprecedented hydroperoxide intermediate 2 formed in solution via an electrophilic attack by hydroxyl and hydroperoxyl radicals of the exocyclic C=C bond of 1. This intermediate was suggested to be rapidly converted into the anionic forms of 2,3-dioxo-1H-indole-5-sulfonic acid (3, m/z 226), 2-amino-alpha-oxo-5-sulfo-benzeneacetic acid (4, m/z 244), and 2-amino-5-sulfo-benzoic acid (5, m/z 216). In the ESI(-)-MS of the indigo carmine solution treated with O(3), two main anions were detected: m/z 216 (5) and 244 (4). Both products were proposed to be produced via an unstable ozonide intermediate. Other anions in this ESI(-) mass spectrum were attributed to be [4 - H + Na](-) of m/z 266, [4 - H](2-) of m/z 121.5, and [5 - H](2-) of m/z 107.5. ESI-MS/MS data were consistent with the proposed structures for the anionic products 2-5.

Electrospray ionization (ESI) mass spectrometry (MS) and tandem mass spectrometry (MS/MS) were used to monitor the oxidation of phenol by a novel heterogeneous Fenton system based on a Fe(0)/Fe(3)O(4) composite and H(2)O(2). On-line ESI-MS(/MS) shows that this heterogeneous system promotes prompt oxidation of phenol to hydroquinone, which is subsequently oxidized to quinone, other cyclic poly-hydroxylated intermediates and an acyclic carboxylic acid. A peroxide-type intermediate, probably formed via an electrophilic attack of HOO(.) on the phenol ring, was also intercepted and characterized. ESI-MS(/MS) monitoring of the oxidation of two other model aromatic compounds, benzene and chlorobenzene, indicates the participation of analogous intermediates. These results suggest that oxidation by the heterogeneous system is promoted by highly reactive HO(.) and HOO(.) radicals generated from H(2)O(2) on the surface of the Fe(0)/Fe(3)O(4) composite via a classical Fenton-like mechanism.

Carbenes and fluorocarbenes are important intermediates in the hydrodechlorination of CFCs catalyzed by metal surfaces. However, the reaction mechanism at a molecular level is not completely understood. In this work, density functional calculations have been performed for the first-row transition-metal complexes M–CH2, M–CHF, and M–CF2 aiming to conbribute to the understanding of the metal/carbene interaction mechanism. Relative energies, geometries, and frequencies of the M–CXY complexes in different electronic states are reported. The binding mechanism is described through an analysis of the molecular orbitals. The binding energy of the M–CF2 is about 30% smaller than the respective M–CH2 binding energy. The electronic configuration of all complexes studied is presented in a diagram that allows one to predict qualitatively properties such as geometries, multiplicities, charge transfers, and relative bond lengths.

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A oxidação do paracetamol (1) promovida pelo sistema TiO 2 /UV em meio aquoso foi investigada. O contínuo monitoramento feito por várias técnicas, tais como espectroscopia UV-Vis, HPLC (cromatografia líquida de alta eficiência), TOC (carbono orgânico total) e ESI-MS (espectrometria de massas com ionização electrospray), mostrou que a remoção do paracetamol foi altamente eficiente, mas com um grau reduzido de mineralização. As análises por GC-MS (cromatografia a gás acoplada a um espectrômetro de massas) indicaram que hidroquinona, ácidos carboxílicos alifáticos, e paracetamol mono e dihidroxilados são os principais produtos formados neste processo de degradação. De acordo com estes resultados, uma rota para degradação do paracetamol induzida pelo sistema TiO 2 /UV foi proposta. A fragmentação dos derivados trimetilsililados (TMS) do monohidróxi e dihidróxi paracetamol, baseada em dados dos espectros de massas, foi também proposta. The advanced oxidation of paracetamol (1) promoted by TiO 2 /UV system in aqueous medium was investigated. Continuous monitoring by several techniques, such as UV-Vis spectroscopy, HPLC (high performance liquid chromatography), TOC (total organic carbon), and ESI-MS (electrospray ionization mass spectrometry), revealed that whereas the removal of paracetamol was highly efficient under these conditions, its mineralization was not likewise accomplished. GC-MS (gas chromatography-mass spectrometry) analysis showed that hydroquinone, aliphatic carboxylic acids, monohydroxy and dihydroxy paracetamol were the main products formed as a result of such degradation process. Based on these results, a reaction route for the degradation of paracetamol induced by the TiO 2 /UV system was suggested. Fragmentation pathways, as obtained from the mass spectra data, were also proposed for the trimethylsilyl (TMS) derivatives of monohydroxy and dihydroxy paracetamol.