- Solvent effects on reactions of hydroxide ion with phosphorus (V) esters. A quantitative treatment
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Second-order rate constants of reactions of HO- with phosphate, phosphinate and thiophosphinate esters, (PhO)2PO.OC6H4NO2-p, Ph2PO.OC6H4NO2-p, Ph2PO.SPh, Ph2PO.SC6H4NO2-p and Ph2PO.SEt, go through minima with decreasing water content of H2O-MeCN or H2O-t-BuOH. The rate decrease is due to stabilization of the non-ionic ester on addition of organic solvent to H2O. This inhibition is partially offset by stabilization of the anionic transition states and in the drier solvents partial desolvation of HO- increases rates.
- Bunton, Clifford A.,Gillitt, Nicholas D.,Kumar, Anurag
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- Temperature-Dependent Reactivity of a Non-heme FeIII(OH)(SR) Complex: Relevance to Isopenicillin N Synthase
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Non-heme iron complexes with cis-FeIII(OH)(SAr/OAr) coordination were isolated and examined for their reactivity with a tertiary carbon radical. The sulfur-ligated complex shows a temperature dependence on ?OH versus ArS? transfer, whereas the oxygen-ligated complex does not. These results provide the first working model for C-S bond formation in isopenicillin N synthase and indicate that kinetic control may be a key factor in the selectivity of non-heme iron "rebound"processes.
- Yadav, Vishal,Siegler, Maxime A.,Goldberg, David P.
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- Structurally homologous sialidases exhibit a commonality in reactivity: Glycoside hydrolase-catalyzed hydrolysis of Kdn-thioglycosides
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Aspergillus fumigatus is one of the main causative agents of invasive aspergillosis, an often-lethal fungal disease that affects immunocompromised individuals. A. fumigatus produces a sialidase that cleaves the nine-carbon carbohydrate Kdn from glycoconju
- Nejatie, Ali,Akintola, Oluwafemi,Steves, Elizabeth,Shamsi Kazem Abadi, Saeideh,Moore, Margo M.,Bennet, Andrew J.
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- Reversible dimerization of mononuclear models of [Fe]-hydrogenase
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Enzyme models on the catwalk! A series of new model complexes of the active site of [Fe]-hydrogenase have been synthesized and characterized. These complexes are monomeric in solution, but dimeric in the solid state. Copyright
- Hu, Bowen,Chen, Dafa,Hu, Xile
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supporting information
p. 6221 - 6224
(2013/07/05)
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- IMIDATE COMPOUND AND USE THEREOF FOR PEST CONTROL
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There is provided a compound having an excellent controlling effect on arthropod pests represented by the formula (I-1): wherein Z represents an optionally substituted carbocyclic group or an optionally substituted heterocyclic group; G represents a -A1-R1
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Page/Page column 217-218
(2009/03/07)
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- Effect of modification of the electrophilic center on the α effect
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We report on a nucleophilic study of esters R-C(=X)-Y-Ar in which the electrophilic center has been modified by replacing O by S in the leaving group or carbonyl center: 4-nitrophenyl acetate (1), S-4-nitrophenyl thioacetate (2), 4-nitrophenyl benzoate (3), and O-4-nitrophenyl thionobenzoate (4). The studies include O- and S- nucleophiles as well as α nucleophiles in H2O at 25.0 ± 0.1°C. The sulfur nucleophile (4-chlorothiophenoxide, 4-ClPhS-) exhibits significant enhanced reactivity for the reactions with thiol and thione esters 2 and 4 compared with their oxygen analogues 1 and 3. On the contrary, the common nucleophile OH- is much less reactive towards 2 and 4 compared with 1 and 3. The effect of changing both the electrophilic center and the nucleofugic center on the reactivity of the other oxygen nucleophiles is not so significant: 4-chlorophenoxide (4-ClPhO-) is four to six times more reactive in the reactions with thiol and thione esters 2 and 4 compared with their oxygen analogues 1 and 3. The α effects exhibited by butan-2,3-dione monoximate (Ox-) and HOO- are strongly dependent on the nature of the electrophilic center of the substrates, indicating that the difference in the ground-state solvation energy cannot be fully responsible for the α effect. Our results clearly emphasize the strong dependence of the α effect on the substrate structure, notably, the nature of the electrophilic center. The impact of change in the nucleofuge (1-→2) and the electrophilic center (3-→4) on reactivity indicates that anucleophiles will need to be "purpose built" for decontamination and nucleophilic degradation of specific biocides.
- Um, Ik-Hwan,Lee, Ji-Youn,Bae, Sun-Young,Buncel, Erwin
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p. 1365 - 1371
(2007/10/03)
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- Diaryl Sulfide Cleavage by Sodium Sulfide in Dipolar Aprotic Solvents
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The interaction of sodium sulfide with diaryl sulfides that possess electron-withdrawing substituents (e. g., cyano or nitro) on the aromatic rings results in cleavage of the thioether and the formation of sodium aryl sulfides in dipolar aprotic solvents.Exchange reactions between these diaryl sulfides and sodium aryl sulfides are also observed in dipolar aprotic solvents.The cleavage and exchange reactions were employed to prepare mixed diaryl or alkyl aryl sulfides from symmetrical diaryl sulfides.
- Evans, Thomas L.,Kinnard, Richard D.
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p. 2496 - 2499
(2007/10/02)
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