C:Corrosive;
76-03-9Relevant articles and documents
Influence of TiO2 Surface on 1,2-Chlorine Shift in β-Chlorine Substituted Radicals As Studied by Radiation Chemistry and Photocatalysis
Mao, Yun,Schoeneich, Christian,Asmus, Klaus-Dieter
, p. 8522 - 8529 (1992)
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.
Selective Hydration of Nitriles to Amides Over Titania Supported Palladium Exchanged Vanadium Incorporated Molybdophosphoric Acid Catalysts
Srinivasa Rao,Srivani,Dhana Lakshmi,Lingaiah
, p. 2025 - 2031 (2016/10/18)
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.]
Thermodynamically leveraged tandem catalysis for ester RC(O)O-R′ bond hydrogenolysis. scope and mechanism
Lohr, Tracy L.,Li, Zhi,Assary, Rajeev S.,Curtiss, Larry A.,Marks, Tobin J.
, p. 3675 - 3679 (2015/06/16)
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.
New acyloxy nitroso compounds with improved water solubility and nitroxyl (HNO) release kinetics and inhibitors of platelet aggregation
Mohamed, Heba A.H.,Abdel-Aziz, Mohamed,Abuo-Rahma, Gamal El-Din A.A.,King, S. Bruce
, p. 6069 - 6077 (2015/11/10)
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.
Nucleofugality of aliphatic carboxylates in mixtures of aprotic solvents and water
Mati, Mirela,Denegri, Bernard,Kronja, Olga
, p. 375 - 384 (2015/10/12)
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.
Atomically precise silver clusters for efficient chlorocarbon degradation
Bootharaju,Deepesh,Udayabhaskararao,Pradeep
, p. 611 - 620 (2013/07/05)
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.
Tandem catalysis of ring-closing metathesis/ atom transfer radical reactions with homobimetallic ruthenium-arene complexes
Borguet, Yannick,Sauvage, Xavier,Zaragoza, Guillermo,Demonceau, Albert,Delaude, Lionel
scheme or table, p. 1167 - 1173 (2011/04/15)
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.
Solvent effect and proton inventory in the hydrolysis of p-methylphenyl trichloroacetate
Frasson, Clea M.L.,Brandao, Tiago A.S.,Zucco, Cesar,Nome, Faruk
, p. 143 - 147 (2007/10/03)
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
Novel cyclohexenyl phenyl carboxamides tocolytic oxytocin receptor antagonists
-
, (2008/06/13)
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.
Novel photoacid generators for photodirected oligonucleotide synthesis
Serafinowski, Pawel J.,Garland, Peter B.
, p. 962 - 965 (2007/10/03)
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.
