- Influence of axial ligands on diverse properties in three trinickel string complexes
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Three new trinickel string complexes, [Ni3(dpa)4(3-nba) 2](1), [Ni3(dpa)4(4-nba)2]·(CH 3OH) (2), and [Ni3(dpa)4(3,5-dnba)2](3) where dpa- is the anion of 2,2-dipyridylamine, 3-nba- is 3-nitrobenzoate anion, 4-nba is 4-nitrobenzoate anion, and 3,5-dnba- is 3,5-dinitrobenzoate anion, were synthesized in good yield and characterized by X-ray crystallography, infrared spectra, elemental analysis, magnetic susceptibility, cyclic voltammogram (CV), UV-vis spectra, fluorescence spectra, and TG analysis. The magnetic susceptibilities suggested that the terminal Ni atoms in all three complexes are in high-spin state while the central Ni atom is in a low-spin state. The CVs of complexes 1-3 showed reversible one-electron redox waves at E1/2 = 1.1395 V for 1, 1.108 V for 2, and 1.109 V for 3 corresponding to Ni3 7+/Ni3 6+. The Ni-Ni distances in three complexes are somewhat different, indicating the axial nitrobenzoate ligands have significant effect on the structural assembly. Supplemental materials are available for this article. Go to the publisher's online edition of Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry to view the supplemental file.
- Zhang, Jing,Zhu, Long-Guan
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Read Online
- Method for synthesizing (2-((4-aminobenzoyl) oxyl) ethyl)sodium
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The invention discloses a method for synthesizing (2-((4-aminobenzoyl) oxyl) ethyl)sodium, and belongs to the technical field of organic synthesis. The method for synthesizing the (2-((4-aminobenzoyl) oxyl) ethyl)sodium is provided to solve the problem that solvent has low boiling point, is easy to volatilize and hard to recover and has great hazard on human bodies and environment in the process of synthesizing the (2-((4-aminobenzoyl) oxyl) ethyl)sodium.
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Paragraph 0010
(2017/04/03)
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- Stabilities of trityl-protected substrates: The wide mechanistic spectrum of trityl ester hydrolyses
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Ionization rates of para-substituted triphenylmethyl (trityl) acetates, benzoates, and para-nitrobenzoates have been determined in aqueous acetonitrile and aqueous acetone at 25 °C. Conventional and stoppedflow techniques have been used to evaluate rate constants ranging from 1.38 × 10-5 to 2.15 × 102S-1 by conductimetry and photospectrometry methods. The varying stabilities of the differently substituted tritylium ions account for a gradual change of reaction mechanism. Poorly stabilized carbocations are generated slowly by the ionization of their covalent precursors and trapped fast by water. Better stabilized carbocations are generated more rapidly and accumulate, so that ionization and trapping by water can be observed as separate steps in a single experiment. Finally, highly stabilized tritylium ions do not react with water, and only the rates of their formation could be measured. The ionization rate constants correlate linearly with Winstein's ionizing powers Y; the low slopes (0.17 + parameters is excellent for symmetrically substituted tritylium derivatives, deviations for unsymmetrically substituted systems are observed. The failing rate-equilibrium relationship between the rates of ionizations (log kion) and the stabilities of the carbocations in aqueous solution (pKR+) may be explained by the late " development of resonance between a p-amino group and the carbocationic center of the tritylium ion during the ionization process.
- Horn, Markus,Mayr, Herbert
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supporting information; experimental part
p. 7469 - 7477
(2010/09/11)
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- Kinetics and mechanism of the formation and decomposition of imidazolin-4-ones from 2-(n-benzoylamino)alkanamides in aqueous medium
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The cyclization reactions of substituted 2-(N-benzoyl-N-methyl)aminoalkanamides 1a-1g have been studied in aqueous medium. The Hammett reaction constant is ρ = 1.4 for the cyclization reactions of compounds 1a-1e in sodium hydroxide solutions. 2-[N-Methyl-N-(4-nitrobenzoyl)amino]-2-(4-nitrophenyl)propanamide (1g) is cyclized to imidazolinone 2g in aqueous amine buffers of pH 9-11.5; the reaction is subject to specific base catalysis in these media, and the rate-limiting step is the formation of a tetrahedral intermediate. In sodium hydroxide solution, the primary cyclization product is hydrolyzed to give an intermediate M which is subsequently decomposed to sodium 4-nitrobenzoate and 2-methylamino-2-(4-nitrophenyl)propanamide. At low sodium hydroxide concentration, the rate-limiting step of the opening of imidazoline ring of compound 2g is non-catalyzed decomposition of the intermediate. At higher sodium hydroxide concentrations, the other reaction path begins to make itself felt: hydroxide-ion-catalyzed decomposition of the intermediate. The dependence of observed rate constant of cyclization of compound 1f on sodium hydroxide concentration was used to determine kinetically the value of pKa = 13.5 ± 0.1. The kinetic deuterium isotope effect of cyclization of compounds 1f giving 2f (kCH / kCD = 1.7) was determined in solutions of NaOD in D2O.
- Sedlak, Milos,Hanusek, Jiri,Bina, Radim,Kavalek, Jaromir,Machacek, Vladimir
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p. 1629 - 1640
(2007/10/03)
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- Effect of solvents on the kinetics and mechanism of the acidic and alkaline hydrolysis of hydroxamic acids
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The acid catalyzed hydrolysis of N-phenylbenzohydroxamic acid (PBHA) C6H5C(=0)N(OH)C6H5 has been studied in aq. dioxane, acetone, dimethylsulphoxide, dimethylformamide, methanol, ethanol and 2-propanol mixtures. Dioxane and methanol have a rate enhancing effect but DMF, acetone, ethanol and 2-propanol exert a rate decreasing effect. In DMSO an increase is followed by a decrease i.e. a rate maximum is observed. An attempt has also been made to study the alkaline hydrolysis of PBHA and two of its derivatives (X-C6H4C(=0)N(OH)C6H5; X=4-NO2, 4-Cl) in aq. dioxane. In all case the pseudo first order rate constant increase with increasing dioxane content. The activation parameters ΔH(+), Δ(+), and ΔGH(+) have been calculated. An attempt has been made to correlate rate data for acidic hydrolysis in terms of solvatochromic parameters and linear free energy relationships.
- Ghosh, Kallol K.,Krishnani, Kishore K.,Ghosh, Sharmistha
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p. 337 - 342
(2007/10/03)
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- Effect of Distortion on the Hydrolytic Reactivity of Amides. 2. N-Pyramidalization: Decomposition of N-Benzoylaziridines in Aqueous Media
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The decomposition of para-substituted N-benzoylaziridines (H, OCH3, NO2, Br) in buffered aqueous media is studied at 25 deg C as a function of pH in order to assess the effect of N-pyramidalization on the hydrolytic reactivity of the amide bond.Overall, the reaction shows three dominant terms: OH- and H2O attack on the neutral form and H2O attack on the protonated form of the amide.In base, the exclusive reaction is rate-limiting and irreversible attack of OH- on the C=O unit leading to normal hydrolytic products.This is shown by the first-order dependence on -> from pH 8 to 14 of the hydrolysis rate and by the fact that ca. 50percent 18O-enriched amide recovered from the hydrolysis medium as a function of time shows no 18O loss.Relative to N,N-dimethylbenzamide (kOH-25 deg C = 6.0 * 10-6 M-1 s-1), N-benzoylaziridine is ca. 200 000-fold more susceptible to OH- attack (kOH-25 deg C = 1.1 M-1 s-1).The kOH- terms follow a ?ρ relationship with ρ = 1.68.In acid, the products are not the expected hydrolytic ones of benzoic acid and aziridine.Rather, exclusive ring opening occurs to give p-X-C6H4C(=O)NHCH2CH2OX.In acetate buffers, product analysis by 1H NMR indicates that the ring-opened material consists of alcohol and acetate (X = H and C(=O)CH3).
- Slebocka-Tilk, H.,Brown, R. S.
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p. 805 - 808
(2007/10/02)
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- Substituent Constants of the Pyrazol, 1,2,3-Triazol, Benzotriazol, and Naphthotriazol Group
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The synthesis of benzoic acids with the title substituents in p- and m-position (15, 13, 11, 9) and their ethyl and methyl esters is described.The ?p and ?m values of the substituents obtained by alkaline hydrolysis of the esters in ethanol/water and methylcellosolve/water demonstrate an inductive electron withdrawing and a mesomer electron donating effect of these groups which are important for dye chemistry.
- Sachweh, Volker,Langhals, Heinz
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p. 1627 - 1639
(2007/10/02)
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- Studies of the Borderline between Concerted and Stepwise Mechanisms of Elimination : E1cB Elimination of Fluoren-9-ylmethyl Carboxylate Esters
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Rates of β-elimination of carboxylate leaving groups from fluoren-9-ylmethyl carboxylate esters in methanolic sodium methoxide at 25 deg C are reported.An E1cB mechanism with rate-determining formation of a carbanion intermediate is assigned on the basis of near identity of measured elimination rates and rates of carbanion formation predicted from a Taft correlation, and the similarity with elimination of 1-(1-acetoxy-1-methylethyl)indene for which the mechanism has been established by Ahlberg and Thibblin.Values of ρ=0.42 and βlg=0.27 measured for substituted benzoate leaving groups are a little larger than expected (ca. 0.24 and 0.18, respectively) and the discrepancy is tentatively ascribed to conformational enhancement of remote substituent effects, rather than to a contribution of E2 elimination.The effects of alkyl and aryl substitution α to the leaving group are discussed, especially in relation to the borderline between concerted and stepwise mechanisms.The measurements fail to confirm an earlier inference that the borderline shows a discontinuity in transition-state structure at the point of mechanistic change.
- O'Ferrall, Rory A. More,Larkin, Finbar,Walsh, Peter
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p. 1573 - 1580
(2007/10/02)
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- Kinetics and Mechanism of Ru(III)-catalysed Oxidation of Aromatic Aldehydes by Sodium Metaperiodate in Alkaline Medium: A Change in Mechanism from Hydride Loss in Acid Medium to Proton Loss in Alkaline Medium
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The title reactions are first order in the substrate and first order in the catalyst, the order with respect to periodate being zero.The dependence on alkali is unity.The reactivity order is p-nitro > m-nitro > m-bromo > m-methoxy > p-bromo > p-chloro- > H ca. p-methyl > p-methoxy.The pH-rate profile attains a minimim at neutral pH and the rate increases on either regions of this pH.The Hammett plot shows a fair linearity with a ρ-value of + 1.66 pointing to a rate-limiting proton loss.A mechanism involving the complexation of the monoanion of the aldehydes with the Ru(III) followed by rate-limiting proton loss is postulated.Activation parameters have been computed.
- Radhakrishnamurti, P. S.,Misra, P. C.
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p. 427 - 430
(2007/10/02)
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