盐酸溶液中阴离子表面活性剂在铝表面上的吸附

用失重法研究了盐酸溶液中阴离子表面活性剂十二烷基磺酸钠（ＤＳＡＳＳ），十二烷基苯磺酸钠（ＤＢＳＡＳ）以及十二烷基硫酸钠（ＳＤＳ）在铝表面上的吸附作用，提出这种吸附作用与铝的失重量有关，且符合Ｌａｎｇ－ｍｕｉｒ方程，计算出吸附热，吸附熵和吸附自由能等热力学参数。认为这种吸附主要靠静电作用，根据接触角的变化讨论了阴离子表面活性剂分子在铝表面上的吸附取向。     

Study of the Reaction 2-(p-Nitrophenyl)Ethyl Bromide + OH(-) in Sulfobetaine Aqueous Micellar Solutions in the Presence and Absence of Added Salts

The reaction of dehydrobromination of 2-(p-nitrophenyl)ethyl bromide with hydroxide ions has been studied in aqueous micellar solutions of N-tetradecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate, SB3-14. The kinetic effects of added salts (NaF, NaCl, NaBr, and NaNO(3)) on the reaction rate in SB3-14 aqueous micellar solutions have also been studied. They were rationalized by considering the binding of the anions, which come from the salt, to the sulfobetaine micelles and their competition with the reactive hydroxide ions for the micellar surface. The equilibrium binding constant of the 2-(p-nitrophenyl)ethyl bromide to the sulfobetaine micelles was estimated by recording the changes in the spectra of the organic substrate when the SB3-14 concentration in the micellar medium changed. This value was in agreement with that obtained from fitting of kinetic data. The second-order rate constant in the micellar pseudophase revealed that the reaction is faster in SB3-14 micelles than in water. This acceleration seems independent of the presence of added salts and can be explained by considering that SB3-14 micelles favor reactions in which charge is delocalized in the transition state. Copyright 2001 Academic Press.     

Imido-osmium(VIII) compounds in organic synthesis: aminohydroxylation and diamination reactions

Imido complexes of osmium tetroxide are versatile compounds for olefin functionalisation. This tutorial review offers a brief historical overview on these compounds and discusses the electronic properties and reactivities of isolated imido osmium compounds in what had been the original stoichiometric aminohydroxylation reaction. The recently emerging catalytic Sharpless aminohydroxylation is discussed with special emphasis on mechanistic details. The final section deals with diamination of olefins, which relies on the chemistry of bisimido and trisimido osmium complexes.     

Solvent effects on substitution reactions at complexes of the [Fe(CN)5L]3- type in binary aqueous mixtures

Summary The kinetics of replacement of 4,4-bipyridine, (4,4-bipy), and 4-cyanopyridine, (4-CNpy), by cyanide in [Fe(CN)₅-(4,4-bipy)]^3-. at 298 K have been studied in binary aqueous mixtures containing different amounts of t-butanol, methanol, glycerol, ethyleneglycol and sucrose. The plots of logarithms of the limiting rate constantsversus the mole fraction of water are linear over the entire composition range studied, showing the importance of solvation phenomena. A different straight line of log (k_L/s^–1)versus X_H2O is obtained for each mixture, indicating the influence of other solvent parameters on the reaction rate. A multiparameter regression of G _exp with A (acidity vector), B (basicity vector) and G^E is used for both reactions; plots of G _calc versus G _exp are linear with slopes of near unity.     

Hydrogen bonding interactions between indole and benzenoid-pi-bases

The NH-pi interactions of indole with benzene, naphthalene, phenanthrene, toluene, m-xylene, and mesitilene, in carbon tetrachloride solutions, have been studied by Fourier transform infrared spectroscopy. The experiments, carried out on the NH stretching band of indole, prove the formation of 1:1 complexes in which the NH bond of indole is engaged. The NH frequency shifts are independent of the number of rings in the base, but they progressively increase as the electron density is enhanced by methylation. The association constants increase with the increase of both, the number of rings and the methyl groups on the base. At higher base concentrations, further shifts on the free NH and associated bands indicate the formation of 1:2 complexes, which suggest hybride NH-pi and van der Waals interactions between one indole ring and two benzene acceptor molecules.     

CF2HCI在金属钨表面上的反应动力学

The unimolecular reaction of CF_2HCl on W filament has been studied. This reaction shows zero order at rather high pressure. The temperature threshold is about 440 ℃. The apparent activation energy of this reaction is 119.7 kJ mol~(-1) which is about a half of the activation energy for homogeneous unimolecular reaction of CF_2HCl, 233.5 kJ mol~(-1).     

Dichloro and alkylchloro gallium derivatives of dichalcogenoimidodiphosphinate ligands: isolation of a spirogallium cation

Dichloro and chloromethyl Ga(III) complexes of general formulae [XClGa-eta2-{R2P(E)NP(E'R'2-E,E'}](X = Cl, R, R'= Ph, E, E'= O (1), S (2), Se (3); R = Ph, R'= OEt, E = O, E'= S (4); R = Me, R'= Ph, E, E'= S (5) and X = Me, E, E'= O (6), S (7), Se (8)) were synthesised by either metathesis reactions between GaCl3 and the potassium salt of the ligand (X = Cl) or by methane eliminations from in situ prepared GaMe2Cl and the protonated ligands LH (X = Me). Redistribution reaction of (3) in either CDCl3 or THF afforded the solvent-free tetracoordinate gallium spirocycle cation [Ga-{eta2-{Ph2P(Se)NP(Se)Ph2-Se,Se'})2]+ (9+). The molecular structures of complexes 2, 4, 5, 7 and 9(+) show non-planar gallacycle rings.     

Increased enantioselectivity in the addition of diethylzinc to benzaldehyde by the use of chiral ligands containing the alpha-phenylethylamino group in combination with achiral ligands

Chiral ligands (S,S)-1, (S,S)-2, (S,S)-3, (S)-4, (S)-5, (S,S)-6, (S,S)-7, and (S,S)-8 turned out to be effective promoters in the enantioselective addition of diethylzinc to benzaldehyde. Interestingly, diamine (S,S)-3 and amino alcohols (S)-5 and (S,S)-7 induce the preferential formation of carbinol (R)-10 (unlike stereoinduction) whereas amido analogues (S,S)-2, (S)-4, and (S,S)-6 favor (S)-10 (like stereoinduction). Molecular modeling at the semiempirical PM3 level provided a reasonable interpretation based on conformational effects in the corresponding transition structures. Combinations of chiral ligands 1-8 with an achiral, flexible ligand (9) gave rise to an activated catalytic system that resulted in faster and higher yielding reactions. Furthermore, substantial increases in the observed enantiomeric excesses of product 10 confirmed the relevant role of achiral bis(sulfonamide) 9 as activator and "chiral environment amplifier".