Motoharu Tanaka

Bio: Motoharu Tanaka is an academic researcher from Nagoya University. The author has contributed to research in topics: Aqueous solution & Acetic acid. The author has an hindex of 26, co-authored 195 publications receiving 2290 citations. Previous affiliations of Motoharu Tanaka include Saga University.

Porphyrins as reagents for trace-metal analysis

Abstract: Several procedures have been proposed to accelerate the slow rate of metalloporphyrin formation. This article describes kinetic and mechanistic aspects of the incorporation of metal ions into porphyrins and their application to the kinetic analysis of traces of metal ions.

Kinetics and Mechanism of Copper(II), Zinc(II), and Cadmium(II) Incorporation into 5,10,15,20-Tetraphenylporphine and N-Methyl-5,10,15,20-tetraphenylporphine in N,N-Dimethylformamide

Abstract: The kinetics of reactions of 5,10,15,20-tetraphenylporphine (H2(tpp)) and N-methyl-5,10,15,20-tetraphenylporphine (H(metpp)) with CuII, ZnII, and CdII ions was studied spectrophotometrically in N,N-dimethylformamide. The rate of incorporation of metal ions (M2+ : Cu2+, Zn2+, Cd2+) into H(metpp) is first order with respect to both H(metpp) and metal ion: d[M(metpp)+]/dt=[k[H(metpp)][M2+] with k(25 °C)=11.5±0.5 mol−1 dm3 s−1 for Zn2+ and (5.8±0.8)×102 mol−1 dm3 s−1 for Cd2+. The rate of incorporation of copper and zinc into H2(tpp) is first order in H2(tpp) and the conditional first-order rate constants are expressed as follows: k0(M)=K[M2+](1+K[M2+])−1(k1+k2[M2+]) where for Cu2+ and Zn2+ K/mol−1 dm3, k1/s−1, and k2/mol−1dm3 s−1 at 25°C are (1.6±0.2)×104 and (7.2±1.5)×102, (1.2±0.1)×10−4 and (3.5±0.7)×10−5, and (5.2±0.2)×10−2 and (8.6±0.2)×10−4, respectively. Metal ion incorporation into H2(tpp) proceeds through the formation of intermediates prior the rate-limiting step. For the H(metpp) system, the methyl...

Water exchange of the (o-phenylenediamine-N,N,N',N'-tetraacetato)ferrate(III) complex in aqueous solution as studied by variable-temperature, -pressure, and -frequency oxygen-17 NMR techniques

Abstract: The crystal structure of potassium aqua (o-phenylenediamine-N,N,N{prime},N{prime}-tetraacetato)ferrate(III) dihydrate, (K(Fe(OH{sub 2})-(phdta)){center dot}2H{sub 2}O), has been determined by x-ray crystallography. The central iron(III) ion is seven-coordinate, with one water molecule being hydrated. Water-exchange rates of the iron(III) complex with phdta{sup 4{minus}} in aqueous solution have been studied as a function of temperature and pressure by the oxygen-17 NMR line-broadening method. Activation parameters for water exchange have been determined as follows: k(25 C) = (1.2 {plus minus} 0.2) {times} 10{sup 7} s{sup {minus}1}, {Delta}H{sup {double dagger}} = 26 {plus minus} 3 kJ mol{sup {minus}1}, {Delta}S{sup {double dagger}} = -22 {plus minus} 9 J K{sup {minus}1} mol{sup {minus}1}, and {Delta}V{sup {double dagger}} = 4.6 {plus minus} 0.2 cm{sup 3} mol{sup {minus}1}. The positive activation volume indicates that the water exchange proceeds via a dissociative interchange mechanism. 41 refs., 4 figs., 4 tabs.

Extraction chemistry of fermentation product carboxylic acids

Abstract: Within the framework of a program aiming to improve the existing extractive recovery technology of fermentation products, the state of the art is critically reviewed. The acids under consideration are propionic, lactic, pyruvic, succinic, fumaric, maleic, malic, itaconic, tartaric, citric, and isocitric, all obtained by the aerobic fermentation of glucose via the glycolytic pathway and glyoxylate bypass. With no exception, it is the undissociated monomeric acid that is extracted into carbon-bonded and phosphorus-bonded oxygen donor extractants. In the organic phase, the acids are usually dimerized. The extractive transfer process obeys the Nernst law, and the measured partition coefficients range from about 0.003 for aliphatic hydrocarbons to about 2 to 3 for aliphatic alcohols and ketones to about 10 or more for organophosphates. Equally high distribution ratios are measured when long-chain tertiary amines are employed as extractants, forming bulky salts preferentially soluble in the organic phase.

Inorganic and bioinorganic solvent exchange mechanisms.

Abstract: Reference LCIB-ARTICLE-2007-010doi:10.1021/cr030726oView record in Web of Science Record created on 2007-02-14, modified on 2017-05-12

Comparing the polarities of the amino acids: side-chain distribution coefficients between the vapor phase, cyclohexane, 1-octanol, and neutral aqueous solution

Abstract: To obtain an indication of the tendencies of amino acids to leave water and enter a truly nonpolar condensed phase, distribution coefficients between dilute solution in water and dilute solution in wet cy- clohexane have been determined for each of the common amino acid side chains at pH 7; they are found to be closely related to the inside-outside distributions of the side chains observed in globular proteins. There was no evidence that excess water enters cyclohexane in association with these solutes. Cyclohexane-to-water distribution coefficients can be combined with vapor-to-water distribution coefficients reported earlier to yield vapor-to-cyclohexane distribution coefficients. Vapor-to-cyclohexane distribution coefficients provide an experimental index of susceptibility to attraction by dispersion forces, and the corresponding free energies are found to be linearly related to side-chain surface areas. Observations using different solvents and variously substituted side chains suggest that alcohols such as 1-octanol exert a specific attraction on the side chain of tryptophan. When less polar phases are used as a reference, leucine, isoleucine, valine, phenylalanine, and methionine are found to be more hydrophobic than tryptophan.

Mechanism of Asymmetric hydrogenation of ketones catalyzed by BINAP/1,2-diamine-ruthenium(II) complexes

Abstract: Asymmetric hydrogenation of acetophenone with trans-RuH(η1-BH4)[(S)-tolbinap][(S,S)-dpen] (TolBINAP = 2,2‘-bis(di-4-tolylphosphino)-1,1‘-binaphthyl; DPEN = 1,2-diphenylethylenediamine) in 2-propanol gives (R)-phenylethanol in 82% ee. The reaction proceeds smoothly even at an atmospheric pressure of H2 at room temperature and is further accelerated by addition of an alkaline base or a strong organic base. Most importantly, the hydrogenation rate is initially increased to a great extent with an increase in base molarity but subsequently decreases. Without a base, the rate is independent of H2 pressure in the range of 1−16 atm, while in the presence of a base, the reaction is accelerated with increasing H2 pressure. The extent of enantioselection is unaffected by hydrogen pressure, the presence or absence of base, the kind of base and coexisting metallic or organic cations, the nature of the solvent, or the substrate concentrations. The reaction with H2/(CH3)2CHOH proceeds 50 times faster than that with D2/(...