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1.
Marc Visseaux Mickael Terrier Andr Mortreux Pascal Roussel 《Comptes Rendus Chimie》2007,10(12):1195-1199
The reaction of one equivalent of Nd(BH4)3(THF)3 with an half equivalent of dialkylmagnesium in the presence of a stoichiometric amount of pentamethylcyclopentadiene cleanly affords a new kind of half-sandwich of neodymium that is stable toward comproportionation. This strategy can be advantageously applied to generate in situ catalysts allowing the controlled polymerisation of isoprene. 相似文献
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Mieczys?aw Makosza Tadeusz Lemek Andrzej Kwast Fran?ois Terrier 《The Journal of organic chemistry》2002,67(2):394-400
Relations of rates of the vicarious nucleophilic substitution of hydrogen (VNS) and S(N)Ar substitution of fluorine in 2-fluoronitrobenzenes with chloroalkyl aryl sulfone carbanions were determined from competitive experiments carried out at various concentrations of base. The observed dependence of the VNS/S(N)Ar rate ratio on the base concentration confirmed the two-step mechanism of the VNS, which consists of reversible formation of sigma(H) adducts of the alpha-chlorocarbanion to nitroarene, followed by base-induced beta-elimination of HCl. It was also evidenced that both of these processes can be the rate-limiting steps: the beta-elimination at low base concentration and the nucleophilic addition at high base concentration. Consistent with that conclusion is the finding that the kinetic isotope effect in the VNS reaction decreases from 4.2 (a value typical of a primary KIE) to 0.8 (a value typical of a secondary KIE) with increasing base concentration. Also reported is our discovery that the S(N)Ar substitution of the 2-fluoronitrobenzenes studied in this work was subject to base catalysis under some of the experimental conditions employed in our competitive experiments. 相似文献
4.
A frontier demarcating superelectrophilic compounds that undergo both Diels-Alder reactivity and σ-complexation reactions, from traditional electrophiles, is afforded through the thermodynamic tendency for σ-complexation as defined by the pKa values for H2O addition to electron-deficient aromatic and heteroaromatic substrates. 相似文献
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J. Terrier D. H. Cook J. H. Axtmayer Ira E. Puddington J. F. Snell und J. L. Perlman 《Fresenius' Journal of Analytical Chemistry》1939,117(5-6):223-225
Ohne Zusammenfassung 相似文献
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A neutron diffraction study has been carried out on a sample of powder of NiI2: the spectrum at 4.2 K shows only a single magnetic line which cannot be indexed on the 2C lattice. Measurements of the specific heat capacity in the region of the transition show the existence of two peaks at the temperatures T1=76K and T2=59.5K, which correspond to singularities in the magnetisation. 相似文献
9.
We became aware, in the course of our on-going research, that the number-average molecular weight of poly(1,4-trans isoprene) determined by conventional gel permeation chromatography (GPC) in tetrahydrofuran (THF) using polystyrene standards differs from its true value by a factor 2. As far as we know, the Mark-Houwink coefficients of this polymer in a widespread GPC eluent such as THF have never been determined. We provide in this contribution a simple relationship between the number-average molecular weight of poly(1,4-trans isoprene) determined by GPC in THF using polystyrene standards and its true value. 相似文献
10.
Peran Terrier D. J. Douglas 《Journal of the American Society for Mass Spectrometry》2010,21(9):1500-1505
At high pH and in the presence of dissolved CO2, the N-terminus and ε-amino groups of amino acids, peptides, and proteins can form carbamino adducts with CO2, R-NH2 + CO2 ↔ R-NHCOO− + H+. We report the first study of carbamino group formation by electrospray ionization (ESI) mass spectrometry (MS). Angiotensin
II, bradykinin, substance P, and insulin have been studied. A careful optimization of the instrumental parameters was necessary
to allow the transfer of the fragile adducts into vacuum for mass analysis. Particularly, dissociation of the adducts in the
ion sampling process and pH changes in ESI must be minimized. With these precautions, levels of carbamino group formation
of angiotensin II and bradykinin determined from mass spectra agree with those expected to be in solution, calculated from
literature equilibrium constants. Thus, ESI MS can quantitatively measure ratios of carbamino adduct to total peptide concentration
in solution. Values of equilibrium constants for carbamino group formation with substance P (pKc = 4.77 ± 0.18) and insulin (pKc = 4.99 ± 0.05) are reported for the first time. 相似文献