Reversible and regioselective reaction of La@C82 with cyclopentadiene

The reversible and regioselective reaction of La@C82 with cyclopentadiene was carried out. The activation and thermodynamic parameter of the retro-reaction was estimated from the Arrhenius plots of the rate constants.     

Mechanism of the reaction of N-p-tosylsulphilimine and related compounds with thiophenolate ion

The reaction of alkyl aryl N-p-tosylsulphilimines with thiophenolate ion was found to afford quantitatively the sulphide that arises by an S_N2 like reaction on the carbon atom adjacent to the tri-valent sulphur atom. This reaction was also found to proceed smoothly with such compounds as sulphoxides and sulphones and sulphoxmanes. The kinetic study on the reaction between aryl methyl N-p-tosylsulphilimine with thiophenolate ion in DMF reveals that the reaction is of second order, namely, first order with respect to each thiophenolate ion and the sulphilimine. The enthalpy and entropy of activation for the reaction are ΔH^≠ = ?17· kcal/mol and ΔS^≠ = ?5·7 eu respectively. The effect of substituents in the reaction, p-XC₆H₄⁺(^?SO₂C₆H₄Y-p)CH₃ + p-ZC₆H₄SK is nicely correl with Hammett σ values giving ?_x = + 2·4, ?_y = + 1·2 and ?_z = ?1·8 respectively. Meanwhile, a marked steric retardation by a bulky alkyl group in alkyl phenyl N-p-tosylsulphilimine is observed. Furthermore, from the stereochemical study of the reaction using an optically active sec-octyl phenyl N-p-tosylsulphilimine with thiophenolate ion it is concluded that the reaction proceeds via a typical S_N2 process on α-carbon atom attached to the tri-valent sulphur atom.     

Terpenoids and aromatic compounds from the New Zealand liverworts Plagiochila, Schistochila, and Heteroscyphus species

A new clerodane- and two new ent-rosane-type diterpenoids have been isolated from the New Zealand liverworts Heteroscyphus billardierii and Plagiochila deltoidea, respectively. The known bisbibenzyl compounds and acetophenones have also been isolated from Schistochila glaucescens and Plagiochila fasciculata. Their structures were established by extensive NMR techniques. Chemosystematics of the Plagiochila species have been discussed.     

Adsorption of anti-human IgG to plasma-polymerized allylamine film formed on a silver plate

Increase in the sensitivity of an immunosensor or biosensor requires the immobilization of a large amount of proteins. Good materials must be developed for this protein adsorption. Allylamine thin film was formed on a flat silver plate by plasma polymerization; this plate is referred to as Ag(ALAM). Ag(ALAM) films were characterized by SEM, FT–IR and ESCA. Investigations on adsorption and desorption of F(ab')₂ anti-human IgG (hIgG) on to Ag and Ag(ALAM) revealed the following: (1) The adsorption isotherm of F(ab')₂ anti-hIgG on to AG(ALAM) or Ag was of a Langmuir type. The binding constant (K_b) and saturation binding (A_b) for this protein on to Ag(ALAM) were 8.93 l/mol and 181.8 nmol/m², respectively, and for Ag, were 7.71 l/mole and 87.9 nmol/m². (2) The extent of desorption of labeled F(ab')₂ anti-hIgG absorbed on the two plates was the same. (3) Ag(ALAM) and Ag were used as solid phases in a two-site immunoradiometric assay of human serum IgG. The dose-response on AG(ALAM) occurred at lower concentration, and was of greater magnitude than that on Ag.     

Synthetic studies of potential antimetabolites. XIII. Synthesis of 7-amino-3-β-d-ribofuranosyl-3H-imidazo[4,5-b] pyridine (1-deazaadenosine) and related nucleosides

7-Amino-3-β-D-ribofuranosyl-3H-imidazo[4,5-b]pyridine (III, 1-deazaadenosine) was synthesized in 32% yield from the diacetyl derivative prepared from 7-aminoimidazo[4,5-b ]pyridine (1-deazaadenine) and 1,2,3,5-tetra-O-acetyl-β-D-ribose by the fusion method. A synthesis of 7-amino-4-b?-D-ribofuranosyl-4H-imidazo[4,5-b]pyridine (IV) was also achieved.     

A thermodynamic analysis of the hydrogen ion titration of micelles

A thermodynamic analysis of hydrogen ion titration is presented for association colloids with particular emphasis on surfactant micelles. When a particular type of the micellar Gibbs-Duhem relation (MGD), alpha(M)dmu(I)+(1-alpha(M))dmu(N)=0 [alpha(M): the degree of ionization of micelles; mu(I),mu(N): chemical potentials of ionized and nonionized species], holds, the free energy change accompanying the ionization of the micelle G(ex) can be evaluated from the titration data in the same manner as for covalently bonded colloids such as linear polyions. In the case where the regular solution approximation is valid for mixed micelles, the titration curve should be a straight line with a slope yielding the interaction parameter, and G(ex) is given as a function of alpha(M)(2). For dodecyldimethylamine oxide micelles for which the MGD relation has been shown to hold, values of the calculated electrostatic free energy G(el) were close to but significantly greater than experimental G(ex) values when the former were calculated on the basis of the Poisson-Boltzmann equation for either a sphere or a plate with smeared charges in a salt solution of infinite volume. When the critical micelle concentration (cmc) data are combined with the hydrogen ion titration data, we obtain a criterion to judge whether the above MGD relation holds or not. When the MGD relation holds, the monomer concentration C(1) can be evaluated from the hydrogen ion titration. For most cases examined, the C(1)/C(1)(alpha(M)=0) from the titration agrees well with cmc/cmc(alpha(M)=0), suggesting cmc=C(1) above the cmc. For tetradecyldimethylamine oxide, the MGD relation does not hold in the range of low ionic strength and even at 0.1 M NaCl it has been found that C(1)/C(1)(alpha(M)=0)相似文献   

Polyhydrazides. IV. Preparation and properties of poly-N-ethyl- and isopropylhydrazide oxadiazoles

High molecular weight poly-N-alkylhydrazide-oxadiazoles have been prepared in poly-phosphoric acid by alkylation of poly-1,3,4-oxadiazole which was synthesized from terephthalic acid and hydrazine sulfate. Various kinds of reagents having an alkoxy group were used as alkylating agent, and N-ethylated and N-propylated polyhydrazides containing oxadiazole units were obtained. The thermal properties of the polymers obtained were investigated by using infrared spectroscopy, viscometry, differential thermometric and thermogravimetric techniques. Soluble poly-N-alkylhydrazide-oxadiazole are thermally cyclized to poly-1,3,4-oxadiazole with elimination of olefins and water at 226–330°C for propylated polydrazide and at 240–360°C for ethylated polyhydrazide. For both, weight loss in polyhydrazides occurs in two distinct stages corresponding, respectively, to cyclization and decomposition of the poly-1,3,4-oxadiazole formed in situ.     

Chemoselective reduction of ketones: trifluoromethylketones versus methylketones

Treatment of an equimolar mixture of trifluoromethylketones (TFMKs) and methylketones (MKs) with Et₂Zn resulted in selective reduction of the TFMKs in good yield. In contrast, treatment of an equimolar mixture of TFMKs and MKs with NaBH₄ in the presence of CeCl₃ in EtOH/H₂O (10:1) at −10 °C reduced only the MKs.     

First synthesis of tetrapyrrolylporphyrin

[reaction: see text] N-alkyl-substituted meso-tetrapyrrolylporphyrin (TPyrP) and its derivatives were synthesized for the first time via an acid-catalyzed condensation between N-alkyl-2,4-diformylpyrrole and unsubstituted pyrrole and a subsequent deformylation reaction. X-ray structural analysis of formyl-substituted TPyrP shows the tilting of meso pyrrole rings ca. 60 degrees to the porphyrin plane. Formyl groups of meso pyrrole rings were removed by treatment with trifluoroacetic acid (TFA) in pyrrole.