- Influence of TiO2 Surface on 1,2-Chlorine Shift in β-Chlorine Substituted Radicals As Studied by Radiation Chemistry and Photocatalysis
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The influence of surface-specific parameters on the photocatalytically induced oxidative degradation of halogenated hydrocarbons in aqueous TiO2 suspensions has been evaluated by comparing the results obtained in this heterogeneous system with those from γ-irradiated homogeneous aqueous solutions.A 1,2-chlorine shift known to occur in β-chlorinated alkyl radicals and the products obtained upon degradation of these radicals (particularly various chloroacetic acids) have been used as markers in these investigations.The results indicated that this chlorine shift, e.g., the rearrangement of CCl3-CH2(.) -> (.)CCl2-CH2Cl, occurs much slower (k in the order of 106 s-1) at the TiO2 surface than the homogeneous solution, where the present data confirm earlier rate constants of >/=108 s-1.This slowdown of the rearrangement process is attributed to steric hindrance in the surface-adsorbed state of the radicals.In the heterogeneous systems the rearrangement can, in fact, be interfered with by peroxidation of the unrearranged radical in the presence of molecular oxygen while such a competition cannot be achieved in the homogeneous solution even at high O2 concentrations.Experimentally, this has been demonstrated, for example, by the fate of the (.)CHCl-CCl3 radical generated upon oxidative C-H cleavage from 1,1,1,2-tetrachloroethane.Direct oxygen addition to this species yields the (.)OOCHCl-CCl3 peroxyl radical which eventually degrades into CCl3COOH.After rearrangement ((.)CHCl-CCl3 -> CHCl2-CCl2(.)) and subsequent peroxidation the then formed CHCl2-CCl2OO(.) peroxyl radical ends up in a completely different acid, namely, CHCl2COOH.It could further be deduced that the 1,2-chlorine shift occurs via a bridged mechanism without transient liberation of the chlorine atom, thereby rendering an alternatively possible chlorine elimination/readdition mechanism an unlikely event.Finally, a marked pH dependence of the product distribution in both the γ-radiolytic and photocatalytic systems is suggested to reflect acid/base catalyzed hydrolysis processes en route of the radical degradation to their final products.
- Mao, Yun,Schoeneich, Christian,Asmus, Klaus-Dieter
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- Selective Hydration of Nitriles to Amides Over Titania Supported Palladium Exchanged Vanadium Incorporated Molybdophosphoric Acid Catalysts
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Abstract: Titania supported palladium exchanged vanadium incorporated molybdophosphoric acid (PdMPAV1) catalysts were prepared and characterized by FT-IR, X-ray diffraction and Laser Raman spectroscopy. The characterization results confirmed the presence of vanadium and palladium into the primary and secondary structure of Keggin ion of heteropoly molybdate respectively. The PdMPAV1 was dispersed on support with intact Keggin ion structure. These catalysts were studied for selective hydration of nitriles to amides. The PdMPAV1was highly active compared to the molybdophosphoric acid containing either vanadium or palladium. The catalyst with 20?% PdMPAV1 dispersed on TiO2 showed highest activity compare to other catalysts. A variety of nitriles were tested over this catalyst and found that the catalyst was active to yield corresponding amides. Different reaction parameters were studied and optimum conditions were established. The PdMPAV1/TiO2 catalyst exhibited consistent activity during reuse. Graphical Abstract: [Figure not available: see fulltext.]
- Srinivasa Rao,Srivani,Dhana Lakshmi,Lingaiah
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p. 2025 - 2031
(2016/10/18)
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- New acyloxy nitroso compounds with improved water solubility and nitroxyl (HNO) release kinetics and inhibitors of platelet aggregation
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New acyloxy nitroso compounds, 4-nitrosotetrahydro-2H-pyran-4-yl 2,2,2-trichloroacetate and 4-nitrosotetrahydro-2H-pyran-4-yl 2,2-dichloropropanoate were prepared. These compounds release HNO under neutral conditions with half-lives between 50 and 120 min, identifying these HNO donors as kinetically intermediate to the much slower acetate derivative and the faster trifluoroacetic acid derivative. These compounds or HNO-derived from these compounds react with thiols, including glutathione, thiol-containing enzymes and heme-containing proteins in a similar fashion to other acyloxy nitroso compounds. HNO released from these acyloxy nitroso compounds inhibits activated platelet aggregation. These acyloxy nitroso compounds augment the range of release for this group of HNO donors and should be valuable tools in the further study of HNO biology.
- Mohamed, Heba A.H.,Abdel-Aziz, Mohamed,Abuo-Rahma, Gamal El-Din A.A.,King, S. Bruce
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p. 6069 - 6077
(2015/11/10)
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- Thermodynamically leveraged tandem catalysis for ester RC(O)O-R′ bond hydrogenolysis. scope and mechanism
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Rapid and selective formal hydrogenolysis of aliphatic ester RC(O)O-R′ linkages is achieved by a tandem homogeneous metal triflate + supported palladium catalytic system. The triflate catalyzes the mildly exothermic, turnover-limiting O-R′ cleavage process, whereas the exothermic hydrogenation of the intermediate alkene further drives the overall reaction to completion.
- Lohr, Tracy L.,Li, Zhi,Assary, Rajeev S.,Curtiss, Larry A.,Marks, Tobin J.
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p. 3675 - 3679
(2015/06/16)
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- Nucleofugality of aliphatic carboxylates in mixtures of aprotic solvents and water
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The leaving group ability (nucleofugality) of fluoroacetate, chloroacetate, bromoacetate, dichloroacetate, trifluoroacetate, trichloroacetate, heptafluorobutyrate, formate, isobutyrate, and pivalate have been derived from the solvolysis rate constants of the corresponding X,Y-substituted benzhydryl carboxylates in 60 % and 80 % aqueous acetonitrile and 60 % aqueous acetone, applying the LFER equation: log k = sf(Ef + Nf). The experimental barriers (ΔG?,exp) for solvolyses of 11 reference dianisylmethyl carboxylates in these solvents correlate very well (r = 0.994 in all solvents) with ΔG?,model of the model σ-assisted heterolytic displacement reaction of cis-2,3-dihydroxycyclopropyl trans-carboxylates calculated earlier. Linear correlation observed between the log k for the reference dianisylmethyl carboxylates and the sf values enables estimation of the reaction constant (sfestim). Using the ΔG?,exp vs. ΔG?,model correlation, and taking the estimated sfestim, the nucleofugality parameters for other 34 aliphatic carboxylates have been determined in 60 % and 80 % aqueous acetonitrile and 60 % aqueous acetone. The most important variable that determines the reactivity of aliphatic carboxylates in aprotic solvent/water mixtures is the inductive effect of the group(s) attached onto the carboxylate moiety.
- Mati, Mirela,Denegri, Bernard,Kronja, Olga
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p. 375 - 384
(2015/10/12)
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- Atomically precise silver clusters for efficient chlorocarbon degradation
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We describe the degradation of chlorocarbons (CCl4, C 6H5CH2Cl and CHCl3) in solution at room temperature (27 ± 4 °C) by the monolayer-protected silver quantum cluster, Ag9MSA7 (MSA: mercaptosuccinic acid) in the presence of isopropyl alcohol (IPA). The main degradation products were silver chloride and amorphous carbon. Benzyl chloride was less reactive towards clusters than CCl4 and CHCl3. Materials used in the reactions and the reaction products were characterized using several spectroscopic and microscopic tools such as ultraviolet-visible (UV/Vis) absorption spectroscopy, Fourier transform infrared spectroscopy (FTIR), photoluminescence spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), energy dispersive analysis of X-rays (EDAX) and scanning electron microscopy (SEM). We have shown that clusters are more efficient for the degradation of halocarbons than the corresponding monolayer-protected nanoparticles (Ag@MSA, particle diameter 15 ± 5 nm) at a given time and temperature. The higher reactivity of clusters is attributed to their small size and large surface area. Clusters and nanoparticles were used for reactions in supported (on neutral alumina) and unsupported forms. A possible mechanism for the reaction has been postulated on the basis of experimental results.
- Bootharaju,Deepesh,Udayabhaskararao,Pradeep
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p. 611 - 620
(2013/07/05)
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- Tandem catalysis of ring-closing metathesis/ atom transfer radical reactions with homobimetallic ruthenium-arene complexes
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The tandem catalysis of ring-closing metathesis/atom transfer radical reactions was investigated with the homobimetallic ruthenium-indenylidene complex [(p-cymene)Ru(μ-Cl)3RuCl(3-phenyl-1-indenylidene)(PCy 3)] (1) to generate active species in situ. The two catalytic processes were first carried out independently in a case study before the whole sequence was optimized and applied to the synthesis of several polyhalogenated bicyclic γ-lactams and lactones from αω-diene substrates bearing trihaloacetamide or trichloroacetate functionalities. The individual steps were carefully monitored by 1H and 31P NMR spectroscopies in order to understand the intimate details of the catalytic cycles. Polyhalogenated substrates and the ethylene released upon metathesis induced the clean transformation of catalyst precursor 1 into the Ru(II)-Ru(III) mixed-valence compound [(p- cymene)Ru(μ-Cl)3RuCl 2(PCy3)], which was found to be an efficient promoter for atom transfer radical reactions under the adopted experimental conditions.
- Borguet, Yannick,Sauvage, Xavier,Zaragoza, Guillermo,Demonceau, Albert,Delaude, Lionel
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scheme or table
p. 1167 - 1173
(2011/04/15)
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- Solvent effect and proton inventory in the hydrolysis of p-methylphenyl trichloroacetate
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Hydrolysis of p-methylphenyl trichloroacetate in water-acetonitrile mixtures was studied as a function of water concentration in the range 5.5-55.5 M. The proton inventory technique, in H2O-D2O mixtures, shows, for a value of D atom fraction in the solvent n = 0.5, deviations from the expected value (for a reaction with one proton being transferred) of 7.5 and 12.3%, for experiments in the presence of 16.6 and 33.3 M L2O (L = H or D), respectively. Theoretical treatment of the data obtained at [L 2O] = 16.6 M using the Gross-Butler equation are consistent with a cyclic transition-state structure with three protons involved. Conversely, similar experiments in the presence of [L2O] = 33.3 M show that multiple water molecules are involved in the transition state of the reaction. Copyright
- Frasson, Clea M.L.,Brandao, Tiago A.S.,Zucco, Cesar,Nome, Faruk
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p. 143 - 147
(2007/10/03)
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- Novel cyclohexenyl phenyl carboxamides tocolytic oxytocin receptor antagonists
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The present invention provides tricyclic carboxamide compounds and methods and pharmaceutical compositions for their use in treatment, prevention, or suppression of disorders which may be remedied or alleviated by oxytocin antagonist activity, including prevention and/or suppression of preterm labor, suppression of labor at term prior to caesarean deliver, and for the treatment of dysmenorrhea. These compounds are also useful in enhancing fertility rates, enhancing survival rates and synchronizing estrus in farm animals; and may be useful in the prevention and treatment of disfunctions of the oxytocin system in the central nervous system including obsessive compulsive disorder (OCD) and neuropsychiatric disorders.
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- Novel pyrido cyclohexenyl phenyl carboxamides tocolytic oxytocin receptor antagonists
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The present invention provides novel tricyclic pyridyl carboxamides as well as methods and pharmaceutical compositions utilizing them compounds for the treatment and/or prevention and/or suppression of disorders which may be remedied or alleviated by oxytocin antagonist activity, including prevention and/or suppression of preterm labor, suppression of labor at term prior to caesarean delivery, and for the treatment of dysmenorrhea. These compounds are also useful in enhancing fertility rates, enhancing survival rates and synchronizing estrus in farm animals; and may be useful in the prevention and treatment of disfunctions of the oxytocin system in the central nervous system including obsessive compulsive disorder (OCD) and neuropsychiatric disorders.
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- Novel photoacid generators for photodirected oligonucleotide synthesis
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Photodirected oligonucleotide synthesis uses either direct or indirect light-dependent 5′-deprotection. Both have been reported to give lower stepwise synthetic yields than conventional methods. The deficiency appears to be due to incomplete deprotection at the oligonucleotide 5′-position and, additionally in the case where photodirection is indirect and uses photogenerated photoacid to effect 5′-detritylation, the depurinating effects of strong acid. We have developed novel photosensitive-2-nitrobenzyl esters that on irradiation with near UV light generate α-chloro-substituted acetic acids, such as trichloroacetic acid, which are widely and successfully used in conventional solid-phase oligonucleotide synthesis. α-Phenyl-4,5-dimethoxy-2-nitrobenzyltrichloroacetate and α-phenyl-4,5-dimethoxy-2,6-dinitrobenzyltrichloroacetate showed appropriate photochemical characteristics and were used for photodirected synthesis of a variety of oligonucleotides, including (T)5, TATAT, TGTGT, (T)10, (AT)5, (CT)5 (GT)5 and (TGCAT)2 on a modified Millipore Expedite DNA synthesizer. The outcomes were compared with those obtained by use of directly added trichloroacetic acid (conventional synthesis). The stepwise yields for the two methods were essentially identical.
- Serafinowski, Pawel J.,Garland, Peter B.
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p. 962 - 965
(2007/10/03)
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- Degradation pathways of trichloroethylene and 1,1,1-trichloroethane by Mycobacterium sp. TA27
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We analyzed the kinetics and metabolic pathways of trichloroethylene and 1,1,1-trichloroethane degradation by the ethane-utilizing Mycobacterium sp. TA27. The apparent Vmax and Km of trichloroethylene were 9.8 nmol min-1 m
- Hashimoto, Akiko,Iwasaki, Kazuhiro,Nakasugi, Naou,Nakajima, Mutsuyasu,Yagi, Osami
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p. 385 - 390
(2007/10/03)
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- Novel hydroxy cyclohexenyl phenyl carboxamides tocolytic oxytocin receptor antagonists
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The present invention provides substituted 10,11-Dihydro-5H-benzo[e]-pyrrolo[1,2-a][1,4]diazepine and 9,10-Dihydro-4H-3a,5,9-triaza-benzo[f]azulene compounds as well as methods and pharmaceutical compositions utilizing these compounds for the treatment and/or prevention and/or suppression of disorders which may be remedied or alleviated by oxytocin antagonist activity, including prevention and/or suppression of preterm labor, suppression labor at term prior to caesarean deliver, and for the treatment of dysmenorrhea. These compounds are also useful in enhancing fertility rates, enhancing survival rates and synchronizing estrus in farm animals.
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- Hydrolytic removal of the chlorinated products from the oxidative free-radical-induced degradation of chloroethylenes: Acid chlorides and chlorinated acetic acids
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Progressive hydrolytic decomposition of acyl chlorides, among them the chlorinated acetyl chlorides, which are produced in the gas-phase oxidation of chlorinated ethylenes, permits the complete mineralization of organically bound chlorine to chloride anion. Hydrolysis rate constants (100% water) have been determined for the following acyl chlorides: acetyl (350 s-1), chloroacetyl (5.5 s-1), dichloroacetyl (300 s-1), trichloroacetyl (>350 s-1), and oxalyl dichloride (>350 s-1). The chlorinated acetyl chlorides thereby give rise to the chloroacetates whose decomposition has also been studied and the kinetic parameters determined. Mono- and dichloroacetate anion undergo hydrolytic dechlorination (kobs = ko + kOH- × [OH-]; ClCH2C(O)O-: Ao 6.4 × 1015 s-1, Eo 148 kJ mol-1, AOH- 1.6 × 109 dm3 mol-1 s-1, EOH- 86 kJ mol-1. Cl2CHC(O)O-: Ao 3.2 × 1016 s-1, Eo 156 kJ mol-1, AOH- 3.2 × 1010 dm3 mol-1 s-1, EOH- 104 kJ mol-1). Trichloroacetate anion decomposes by another mechanism, undergoing decarboxylation which is base-uncatalyzed: Ao 2.1 × 1017 s-1, Eo 146 kJ mol-1. Procedures on a pilot-plant scale are pointed out that allow the elimination of these compounds upon oxidation of the strip-gas produced when contaminated water is freed from chlorinated ethylenes by air-stripping.
- Prager, Lutz,Dowideit, Peter,Langguth, Helmut,Schuchmann, Heinz-Peter,Von Sonntag, Clemens
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p. 1641 - 1647
(2007/10/03)
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- Effects of bromide on the formation of THMs and HAAs
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The role of bromide in the formation and speciation of disinfection by-products (DBPs) during chlorination was investigated. The molar ratio of applied chlorine to bromide is an important factor in the formation and speciation of trihalomethanes (THMs) and halogenacetic acids (HAAs). A good relationship exists between the molar fractions of THMs and the bromide incorporation factor. The halogen substitution ability of HOBr and HOCl during the formation of THMs and HAAs can be determined based on probability theory. The formation of HAAs, and their respective concentrations, can also be estimated through use of the developed model.
- Chang,Lin,Chiang
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p. 1029 - 1034
(2007/10/03)
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- Kinetics and mechanism of the oxidation of aliphatic aldehydes by tetrabutylammonium tribromide
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The oxidation of six aliphatic aldehydes by tetrabutylammonium tribromide (TBATB) in aqueous acetic acid resulted in the formation of corresponding carboxylic acids. The reaction is first order with respect to TBATB and the aldehydes. The oxidation of deuteriated acetaldehyde (MeCDO) showed the presence of substantial kinetic isotope effect (kH/kD = 5.92 at 298 K). Addition of tetrabutylammonium chloride has no effect on the reaction rate. Tribromide ion has been proposed as the reactive oxidizing species. The rate constants correlate well with Taft's σ* values, the reaction constant being negative. A mechanism involving a hydride-ion transfer from the aldehyde hydrate to the oxidant in the rate-determining step has been suggested.
- Baghmar, Manju,Sharma, Pradeep K.
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p. 390 - 395
(2007/10/03)
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- Kinetics and mechanism of oxidation of aliphatic aldehydes by pyridinium chlorochromate
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Oxidation of six aliphatic aldehydes by pyridinium chlorochromate (PCC), in dimethyl sulphoxide (DMSO), to the corresponding carboxylic acids, is first order each in PCC, the aldehyde and hydrogen ion. The oxidation of deuteriated acetaldehyde, MeCDO, exhibits a substantial primary kinetic isotope effect (kH/kD = 6.12 at 288 K). The oxidation of acetaldehyde has been studied in nineteen different organic solvents. The solvent effect has been analysed using Taft's and Swain's multiparametric equations. The rate constants correlate well with Taft's σ* values; reaction constants being negative. A mechanism involving transfer of hydride ion has been suggested.
- Saraswat,Sharma,Banerji
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p. 583 - 587
(2007/10/03)
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- The formation and control of disinfection by-products using chlorine dioxide
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In this study, chlorine dioxide (ClO2) was used as an alternative disinfectant with vanillic acid, p-hydroxybenzoic acid, and humic acid as the organic precursors in a natural aquatic environment. The primary disinfection by-products (DBPs) formed were trihalomethanes (THMs) and haloacetic acids (HAAs). Under neutral conditions (pH = 7) for vanillic acid, more total haloacetic acids (THAAs) than total trihalomethanes (TTHMs) were found, with a substantial increase during the later stages of the reaction. In the case of p-hydroxybenzoic acid, the amount of THAAs produced was minimal. Raising the concentration of ClO2 was not favorable for the control of THAAs in low concentrations of vanillic acid. ClO2 could reduce the total amount of TTHMs and THAAs for higher concentration of vanillic acid. It was found that the humic acid treatment dosage was not significant. Under alkaline conditions (pH = 9), the control of TTHMs and THAAs for the treatment of vanillic acid was better and more economical, however, an appreciable amount of inorganic by-products were observed. Under the same alkaline condition, the control of THAA for the treatment of p-hydroxybenzoic acid was not beneficial and for the treatment of humic acid was not significant. (C) 2000 Elsevier Science Ltd.
- Chang, Chen-Yu,Hsieh, Yung-Hsu,Shih, I-Chen,Hsu, Shen-Sheng,Wang, Kuo-Hua
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p. 1181 - 1186
(2007/10/03)
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- Benzimidazole compounds
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Benzimidazole-4-carboxamide compounds (I) which can act as potent inhibitors of the DNA repair enzyme poly(ADP-ribose) polymerase or PARP enzyme (EC 2.4.2.30), and which thereby can provide useful therapeutic compounds for use in conjunction with DNA-damaging cytotoxic drugs or radiotherapy to potentiate the effects of the latter. In formula (I), R and R' may each be selected independently from hydrogen, alkyl, hydroxyalkyl (e.g. CH2CH2OH), acyl (e.g. acetyl or benzoyl) or an optionally substituted aryl (e.g. phenyl) or aralkyl (e.g. benzyl or carboxybenzyl) group. R is generally a substituted phenyl group in the most preferred compounds. The compounds may also be used in the form of pharmaceutically acceptable salts or pro-drugs.
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- Topiramate immunoassay
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The present invention provides a topiramate immunoassay and reagents for use in the immunoassay. In particular, topiramate is derivatized at the sulfamate moiety or the 9-carbon or 10-carbon methyl group of topiramate to add a label bound directly or through a linking group for use as a tracer (competitive analyte analog) or to add a linking group bound to a carrier for use as an immunogen to induce anti-topiramate antibodies. Immunoassay methods and kits are also provided.
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- Formation of the haloacetic acids during ozonation and chlorination of water in warsaw waterworks (Poland)
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The results of the study of the HAAs formation in Water Works in Warsaw, Poland are presented. Water taken from Zegrzynskie Lake is characterized by elevated content of humic substances and algae bloom in hot seasons. The water is ozonated and chlorinated
- Dojlido, Jan,Zbiec, Edward,Swietlik, Ryszard
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p. 3111 - 3118
(2007/10/03)
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- Evidence for an additional oxidant in the photoassisted Fenton reaction
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The photo-Fenton reaction (Fe3+ + H2O2 + UV) has potential applications in wastewater treatment. This reaction was compared to H2O2 photolysis and other reactions that produce only hydroxyl radicals (OH·) in order to probe for additional or alternative intermediates that may contribute to the recognized potency of photo-Fenton as an oxidant of organic compounds. Distinct differences were found between photo-Fenton and genuine OH· reactions. The kinetic deuterium isotope effect (KDIE) for cyclohexane in the photo-Fenton reaction increases from 1.2 to 1.4 with increasing concentration of OH· scavenger, tert-butyl alcohol; whereas the KDIE in genuine OH· reactions (H2O2/UV, Fe3+/UV, and Fe2+ + H2O2) is 1.1 and unchanged in the presence of tert-butyl alcohol. Photo-Fenton catalyzed the epoxidation of cyclohexene at a much greater rate than H2O2/UV. The relative yields of chlorinated organic acids from 1,1,2-trichloroethane, trichloroethene, and tetrachloroethene oxidation were markedly affected by the presence of iron. Time-resolved laser flash photolysis spectroscopy in the absence of organics revealed a transient, seen only in Fe3+ + H2O2 solutions, with broad absorbance in the visible and a lifetime of ~100 ns. The results suggest the participation of a high-valent oxoiron complex (ferryl) in addition to OH· in organic compound oxidations. Hydrogen peroxide forms a complex with iron, Fe(O2H)2+ (K15 = 1.15 x 10-2), that absorbs in the visible region and could be the precursor of the ferryl complex. The photo-Fenton reaction (Fe3+ + H2O2 + UV) has potential applications in wastewater treatment. This reaction was compared to H2O2 photolysis and other reactions that produce only hydroxyl radicals (OH·) in order to probe for additional or alternative intermediates that may contribute to the recognized potency of photo-Fenton as an oxidant of organic compounds. Distinct differences were found between photo-Fenton and genuine OH· reactions. The kinetic deuterium isotope effect (KDIE) for cyclohexane in the photo-Fenton reaction increases from 1.2 to 1.4 with increasing concentration of OH· scavenger, tert-butyl alcohol; whereas the KDIE in genuine OH· reactions (H2O2/UV, Fe3+/UV, and Fe2+ + H2O2) is 1.1 and unchanged in the presence of tert-butyl alcohol. Photo-Fenton catalyzed the epoxidation of cyclohexene at a much greater rate than H2O2/UV. The relative yields of chlorinated organic acids from 1,1,2-trichloroethane, trichloroethene, and tetrachloroethene oxidation were markedly affected by the presence of iron. Time-resolved laser flash photolysis spectroscopy in the absence of organics revealed a transient, seen only in Fe3+ + H2O2 solutions, with broad absorbance in the visible and a lifetime of approx. 100 ns. The results suggest the participation of a high-valent oxoiron complex (ferryl) in addition to OH· in organic compound oxidations. Hydrogen peroxide forms a complex with iron, Fe(O2H)2+ (K15 = 1.15 × 10-2), that absorbs in the visible region and could be the precursor of the ferryl complex.
- Pignatello, Joseph J.,Liu, Di,Huston, Patrick
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p. 1832 - 1839
(2007/10/03)
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- Hydrolysis of haloacetonitriles: Linear free energy relationship. Kinetics and products
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The hydrolysis rates of mono-, di- and trihaloacetonitriles were studied in aqueous buffer solutions at different pH. The stability of haloacetonitriles decreases and the hydrolysis rate increases with increasing pH and number of halogen atoms in the molecule. The monochloroacetonitriles are the most stable and are also less affected by pH-changes, while the trihaloacetonitriles are the least stable and most sensitive to pH changes. The stability of haloacetonitriles also increases by substitution of chlorine atoms with bromine atoms. The hydrolysis rates in different buffer solutions follow first order kinetics with a minimum hydrolysis rate at intermediate pH. Thus, haloacetonitriles have to be preserved in weakly acid solutions between sampling and analysis. The corresponding haloacetamides are formed during hydrolysis and in basic solutions they can hydrolyze further to give haloacetic acids. Linear free energy relationship can be used for prediction of degradation of haloacetonitriles during hydrolysis in water solutions. The hydrolysis rates of mono-, di- and trihaloacetonitriles were studied in aqueous buffer solutions at different pH. The stability of haloacetonitriles decreases and the hydrolysis rate increases with increasing pH and number of halogen atoms in the molecule: The monochloroacetonitriles are the most stable and are also less affected by pH-changes, while the trihaloacetonitriles are the least stable and most sensitive to pH changes. The stability of haloacetonitriles also increases by substitution of chlorine atoms with bromine atoms. The hydrolysis rates in different buffer solutions follow first order kinetics with a minimum hydrolysis rate at intermediate pH. Thus, haloacetonitriles have to be preserved in weakly acid solutions between sampling and analysis. The corresponding haloacetamides are formed during hydrolysis and in basic solutions they can hydrolyze further to give haloacetic acids. Linear free energy relationship can be used for prediction of degradation of haloacetonitriles during hydrolysis in water solutions.
- Glezer, Victor,Harris, Batsheva,Tal, Nelly,Iosefzon, Berta,Lev, Ovadia
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p. 1938 - 1948
(2007/10/03)
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- Metabolism of trichloroethylene and chloral hydrate by the Japanese medaka (Oryzias latipes) in vitro
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Trichloroethylene (TRI), a common groundwater contaminant, is readily metabolized by mammals to produce chloral hydrate (CH), trichloroacetic acid (TCA), and trichloroethanol (TCOH). Cytochrome P450 (CYP) and other enzymes are responsible for formation of these metabolites, which are implicated in TRI's toxicity and carcinogenicity. To establish the validity of the Japanese medaka (Oryzias latipes) as an alternate test species for TRI, we examined the metabolism of TRI and CH, as well as CYP expression, in medaka liver preparations. Trichloroethylene was incubated with medaka microsomal protein, and metabolites were extracted and analyzed using gas chromatography. Microsome-mediated metabolism of TRI was observed, and a K(m) value for TRI oxidation of 540 μM and a V(max) value of 213 pmol/min·mg-1 protein were obtained. Conversion of TRI to CH, TCA, and TCOH was found with medaka hepatic subcellular fractions. In addition, a sex difference in hepatic microsomal TRI metabolism, specific CYP content, and ethoxyresorufin O- deethylase activity was noted. The lower specific activity of preparations from the livers of female medaka is compensated for by increased total protein in the larger liver mass of the female. Immunochemical analysis showed that CYP1A was readily detectable in medaka liver, but CYP2E1 was present at very low levels. These data suggest that TRI metabolism in medaka liver preparations mimics that observed in mammalian systems and supports their use as an alternative test species in the evaluation of the toxicity of TRI.
- Lipscomb, John C.,Confer, Patricia D.,Miller, Michael R.,Stamm, Steven C.,Snawder, John E.,Bandiera, Stelvio M.
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p. 325 - 332
(2007/10/03)
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- Benzamide analogs useful as PARP (ADP-ribosyltransferase, ADPRT) DNA repair enzyme inhibitors
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A range of 3-oxybenzamide compounds and related quinazolinone compounds are disclosed which can act as potent inhibitors of the DNA repair enzyme poly(ADP-ribose) polymerase or PARP enzyme (EC 2.4.2.30), and which thereby can provide useful therapeutic compounds for use in conjunction with DNA-damaging cytotoxic drugs or radiotherapy to potentiate the effects of the latter. The compounds disclosed include 3-benzyloxybenzamides, 3-oxybenzamides in which a chain of 5 or more methylene groups terminate in a halogen atom or in a purin-9-yl moiety, certain benzoxazole-4-carboxamide compounds and certain quinazolinone compounds. In formula X and Y together may form a bride -X-Y- that represents the grouping (a), (b) or (c )wherein R5 is H, alkyl, aryl or aralkyl.
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- Kinetics and Formation Mechanism of Nitroethylene from Nitroethyl Esters of Aliphatic Carboxylic Acids
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Thermal decomposition of nitroethyl carboxylates of aliphatic acids in gas phase within temperature range 205-245°C up to conversion 70-80% follows the law of first order reaction resulting in nitroethylene and the corresponding acid. Reaction is complicated by heterogeneous processes but at S/V 0.53-0.54 cm-1 the rate constant is close to that of homogeneous decomposition. The initial pressure of the compound's vapor (at p0 > 100 mm Hg) and addition of inhibitors of chain reactions (tolyene, nitrogen oxide) do not affect the rate of decomposition. At decrease of the pKa of acid from 4.86 to 0.66 the decomposition rate increases 2.5-fold.
- Stepanov,Kruglyakova
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p. 1395 - 1397
(2007/10/03)
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- Halogen atom transfer radical cyclization of N-allyl-N-benzyl-2,2-dihaloamides to 2-pyrrolidinones, promoted by Fe0-FeCl3 or CuCl-TMEDA
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The halogen atom transfer radical cyclization of a N-allyl-N-benzyl-2,2-dihaloamides to 2-pyrrolidinones has been carried out in high yields under mild conditions, in a reaction promoted by CuCl-TMEDA or Fe0-FeCl3 in acetonitrile or N,N-dimethylformamide, respectively.
- Benedetti, Miriam,Forti, Luca,Ghelfi, Franco,Pagnoni, Ugo Maria,Ronzoni, Roberto
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p. 14031 - 14042
(2007/10/03)
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- Oxidation of aldehydes with permanganate in acidic and alkaline media
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The oxidation mechanism of aldehydes with permanganate was studied in acidic and alkaline media on acetaldehyde, propionaldehyde, pivalaldehyde (2,2′-dimethylpropanal) and chloral substrates. On addition of water to acetaldehyde dissolved in organic solvents the rate increased, and therefore it may be stated that the hydrate form is more reactive than the aldehyde form. Acid-catalysed nucleophilic addition of permanganate is suggested. In alkaline medium a mechanism based on electron abstraction from the alkoxy anion of the hydrate is proposed. Deprotonation constants of hydrate could be calculated..
- Jaky,Szammer
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p. 420 - 426
(2007/10/03)
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- Pyrimidines
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Compounds of the formula I STR1 in which R1 to R6 have the stated meanings, and the readily water-soluble salts of these compounds, and a process for the preparation thereof are described. The compounds are suitable for the treatment of lipid metabolism disorders which are beneficially influenced by a stimulation of the hepatic LDL receptor. Also described are compounds of the formula II STR2 and the salts thereof.
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- Metallocenes as anti-tumor drugs
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The invention relates to novel titanocene derivatives possessing chemotherapeutic activity and method for their preparation. These compounds possess two cyclopentadiene rings linked to titanium as a central atom and bound covalently to two phenoxy groups which possess a substituent R selected from the group consisting of COOCH3, COOC2 H5, H, COOCH2 CH2 OCH2 CH2 OCH3 and are free from amino, nitro, chloride and fluoride groups. The novel compounds represent a compromise between the main properties for an antitumor agent, i.e., electrophilicity and stability, being water soluble. Cytotoxicity measurements of these compounds showed significant growth inhibition properties, expressed in terms of IC50 [M] values.
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- Kinetics and mechanism of the hydrolysis of 1-aryloxyethyl alkanoates
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The kinetics and mechanism of the hydrolysis of 1-aryloxyethyl alkanoates are reported.In acidic media, 18O isotope exchange studies, kinetics, activation parameters and substituent effects point clearly to an AAl-1 mechanism with the formation of an alkoxycarbonium ion as the rate-limiting step.In basic media the data indicate a conventional BAc-2 mechanism through attack of hydroxide ion on the carbonyl carbon.In neutral medium (pH 2.5-8.8) there is a certain amount of conflicting evidence which leads, however, to the proposal that hydrolysis occurs via attack of a water molecule on the acyl carbon as the rate-limiting step.
- Hall, C. Dennis,Goulding, Celia W.
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p. 1471 - 1478
(2007/10/02)
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- REACTION OF 1-(ACYLCARBAMOYL)-3,5,5-TRIMETHYL-2-PYRAZOLINES WITH NUCLEOPHILIC REAGENTS
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1-(Acylcarbamoyl)-3,5,5-trimethyl-2-pyrazolines react with water and alcohols to form 3,5,5-trimethyl-4,5-dihydro-1H-pyrazole-1-carboxamide with the elimination of substituted carboxylic acids. 1-(Benzoylcarbamoyl)-3,5,5-trimethyl-2-pyrazoline and 3,5,5-trimethyl-4,5-dihydro-1H-pyrazole-1-carboxamide form 2:1 complexes with Cu(II) ions.
- Zobova, N. N.,Nazyrova, A. Z.
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p. 1906 - 1908
(2007/10/02)
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- Identification of Organic Acids and Other Intermediates in Oxidative Degradation of Chlorinated Ethanes on TiO2 Surfaces en Route to Mineralization. A Combined Photocatalytic and Radiation Chemical Study
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The oxidative degradation of chlorinated ethanes proceeds practically via the same mechanism in γ-radiolysis and photocatalysis at TiO2 surfaces, respectively.C-centered radicals generated via hydroxyl radical induced C-H bond cleavage and peroxyl radicals derived therefrom after oxygen addition are the key radical intermediates in these processes.The main molecular products identified and isolated in both the γ-radiolytic and photocatalytic experiments are organic (mostly chlorinated) acids, HCl, and CO2.Other products formed in minor yields are aldehydes and HCOOH.Photocatalytic degradation of these product acids and nonionic substrates leads eventually to complete mineralization.The results strongly suggest that the photocatalytic degradation is initiated by an oxidation of the chlorinated compounds through TiO2-surface-adsorbed hydroxyl radicals.Only some acids, like trichloroacetic acid and oxalic acid, seem to be oxidized primarily by valence band holes via a photo-Kolbe process.Several rate constants are reported on the oxidation of chlorinated ethanes and acids by free and surface-adsorbed hydroxyl radicals and on the overall photocatalytic degradation of the chlorinated compounds.The paper also includes a discussion of the material balance.The study demonstrates the value of radiation chemical investigations for the understanding of the details in the photocatalytic mineralization process of halogenated organic compounds.
- Mao, Yun,Schoeneich, Christian,Asmus, Klaus-Dieter
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p. 10080 - 10089
(2007/10/02)
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- EVIDENCE OF ESTERIFICATION DURING THE OXIDATION OF SOME AROMATIC ALDEHYDES BY CHROMIUM (VI) IN ACID MEDIUM AND THE MECHANISM OF THE OXIDATION PROCESS
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The oxidation kinetics of some aromatic aldehydes by chromium (VI) have been studied in perchloric acid medium.Kinetic and spectrophotometric results indicate the formation of a 1:1 intermediate ester between the reactive chromium (VI) species and protonated benzaldehyde.The rate is directly proportional to the square of hydrogen ion concentrations.The rate of oxidation decreases with the presence of electron donating groups and increases with electron withdrawing groups on the aromatic ring.The activation parameters associated with the rate determining step and the thermodynamic values associated with the equilibrium step have been computed.An attempt has been made to compare the results obtained with those for the oxidations of some aliphatic aldehydes which do not have enolizable hydrogen.
- Gupta, Kalyan Kali Sen,Dey, Sanghamitra,Gupta, Shipra Sen,Adhikari, Mrityunjoy,Banerjee, Amalendu
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p. 2431 - 2444
(2007/10/02)
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- Preparation and Kinetics of the Hydrolysis of Trichloromethyl Esters
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The rates of the hydrolysis of trichloromethyl trichloroacetate and trifluoroacetate have been measured in aqueous acetonitrile and dioxane solutions of low water content.The rates and activation parameters are found to be identical with those for phosgene.It is proposed that the very fast neutral BAC3 ester hydrolysis is followed by a fast decomposition of the initially formed trichloromethanol to phosgene, the hydrolysis of which is the rate-determining stage.
- Euranto, Erkki K.,Kanerva, Liisa T.
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p. 717 - 720
(2007/10/02)
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- KINETICS AND MECHANISM OF THE OXIDATION OF ALIPHATIC ALDEHYDES BY SODIUM N-BROMOARYLSULPHONAMIDES IN ACID SOLUTION
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The oxidation of aliphatic aldehydes to the corresponding carboxylic acids by sodium N-bromoarylsulphonamides (N-bromoamines) is first order with respect to the oxidant, the aldehyde and hydrogen ions.In the oxidation of acetaldehyde at 298 K, the primary kinetic isotope effect, kH/kD is 4.91 +/- 0,14 and the solvent isotope effect, k(H2O)/k(D2O), is 0.43.Addition of the parent sulphonamide does not affect the rate.The reduction of six substituted N-bromoamines exhibited a reaction constant of 1.22 at 298 K. (ArSO2NH2Br)+ is postulated as the reactive oxidising species.Separate rate constants for the oxidation of aldehyde hydrate and free aldehyde forms have been computed.The rates of the oxidation of the aldehyde hydrates correlate well with Taft's substituent constants with negative reaction constants.A mechanism involving hydride transfer from the aldehyde hydrate to the oxidant is proposed.
- Banerji, Kalyan K.
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p. 5949 - 5954
(2007/10/02)
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- Kinetics and Mechanism of the Oxidation of Aldehydes by N-Bromoacetamide
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The kinetics of the oxidation of a series of seven aldehydes by N-bromoacetamide (NBA) have been studied in acid as well as alkaline solution.The product of the oxidation is the corresponding carboxylic acid.The reaction is first order with respect to the aldehyde and NBA.In acid solution, there is a first order dependence of the rate on .The increase in the decreases the rate of oxidation in alkaline solution.The reaction rate is decreased by the addition of acetamide.The oxidation of acetaldehyde indicated the absence of a primary kinetic isotope effect.Using the equilibrium constants for aldehyde hydration reaction, the rate constants for the oxidation of aldehyde hydrate and the free aldehyde have been computed.The rates of oxidation of aldehyde hydrates in acid solution correlate well in Taft's equation; the value of reaction constant ρ* being -1.73 at 298 K.No such correlation was observed when the rates of the oxidation of free aldehydes were considered.Similarly, the relative rates of oxidation in alkaline solution were easily explained if the oxidation of aldehyde hydrates was assumed. (H2OBr)(+) and hypobromite ions have been postulated as the reactive oxidising species in acid and alkaline solution respectively.The proposed mechanism in both the media involves initial formation of a hypobromite ester, which then decomposes to the carboxylic acid.
- Sharma, Vinita,Banerji, Kalyan K.
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p. 3551 - 3574
(2007/10/02)
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- Kinetics and Mechanisms of the Neutral and Acid-catalysed Hydrolyses of Chloro-substituted Alkyl Acetates in Aqueous Solutions of Constant Ionic Strength
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The simultaneous neutral and acid-catalysed hydrolyses of different chloro-substituted alkyl acetates in water and in aqueous acetone solutions have been studied using electrolyte solutions of constant ionic strength.The mechanism of the acid-catalysed hydrolyses of monochloroesters is AAC2.When an ester has two chloro-substituents the acid-catalysed hydrolysis takes place simultaneously by the AAC2 and A-BAC3 mechanisms and in the case of trihalogenated esters the mechanism is A-BAC3, a mechanism with an unsymmetrically catalysed partition of the intermediate formed from the water-catalysed addition of water to the carbonyl group of the ester.Structural and solvent effects of these reactions are discussed.
- Euranto, Erkki K.,Kanerva, Liisa T.,Cleve, Nils J.
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p. 2085 - 2092
(2007/10/02)
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- Kinetics and Mechanism of the Oxidation of Aliphatic Aldehydes by Acid Permanganate
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The kinetics of the oxidation of seven aliphatic aldehydes by acid permanganate have been studied in aqueous solution.The product of the reaction is the corresponding carboxylic acid.The reaction is first order in the oxidant, aldehyde and hydrogen ions.The oxidation of acetaldehyde exhibited a primary kinetic isotope effect, kH/kD = 6.08+/-0.06 at 298 K.Using the equilibrium constants for aldehyde hydration reaction, the rate constants for the oxidation of the hydrate form and the free aldehyde have been computed.The rates of oxidation of aldehyde hydrates correlate well in Taft's equation; the values of reaction constant ρ* being -1.51 at 298 K.No such correlation is observed when the rates of oxidation of free aldehydes were considered.The results support a mechanism consisting of a rate-determining transfer of a hydride ion from the aldehyde hydrate to the oxidant.
- Jain, Anandi L.,Banerji, Kalyan K.
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p. 678 - 692
(2007/10/02)
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- Esters of 1-hydroxy-1H-imidazo-(4,5-b)-pyridines as herbicides
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Ethers and esters of 1-hydroxy-2-(1,1-difluoroalkyl)-1H-imidazo(4,5-b)pyridine compounds, useful as herbicides.
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