bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Surfactant Micelles on the Rate of Reaction of Tetranitromethane with Hydroxide Ion
Authors: Harada Tsuyoshi , Nishikido Nagamune , Moroi Yoshikiyo , Matuura Ryohei
Published: July 2006

The rates of trinitromethanide anion formation by the reaction of tetranitormethane with hydroxide ion were measured in the presence of anionic, cationic and nonionic surfactant micelles in aqueous solutions. Using the analytical approach which takes into consideration the distribution of hydrophobic reactants among micelles, k1 (a second-order rate constant on micelles associated with one reactant molecule) and K1/N(K1: an association constant of the reactant with micelles having no reactant, N: an aggregation number of surfactant molecule in a micelle) were estimated. The anionic surfactant exhibited no effect on the reaction rate. In the case of cationic surfactants, both k1 and K1 values increased not only with alkyl chain length but also with hydrophobicity of the surfactants. In the case of nonionic surfactants, an increase of alkyl chain length with a given oxyethylene unit resulted in an increase in the k1 values, while an increase of oxyethylene group with the fixed alkyl chain length resulted in an appearance of the maximum k1 value. From temperature dependence of the reaction rate, a stabilization of the activated complex could be explained by an electrostatic interaction of the complex with the charged micellar surface. It was also found from the analytical approach that the distribution of tetranitromethane among micelles used in the present experiment could be approximated by the Poisson distribution.
Raman Spectra of a Compound under Inversion Motions. II. N-Methylpiperazine
Authors: Fukushima Kunio , Takahashi Hiromichi
Published: July 2006

Raman spectra of N-methylpiperazine in proton donors and acceptors were measured. Forms of stable conformers in the donors and the acceptors were studied by comparison of the Raman spectra and normal vibration calculations. A conformational change of the molecule in the donors was found, suggesting the change of valence state of nitrogen atom, which is caused by hydrogen bonding.
Studies on Room Temperature Phosphorometric and Delayed Fluorometric Analysis. I. Delayed Fluorometric Analysis of Porphyrin Derivatives
Authors: Onoue Yoshiaki , Hiraki Keiz\={o} , Nishikawa Yasuharu
Published: July 2006

The spectral characteristics and its application to measurement of porphyrins were investigated by use of room temperature phosphorometry. Certain porphyrin compounds adsorbed on filter paper exhibit intense E-type delayed fluorescence. This could be utilized for the determination of porphyrin derivatives.
Kinetics and Mechanism of Cobalt(II) Incorporation into meso-Tetra(4-pyridyl)porphine in Acetic Acid
Authors: Funahashi Shigenobu , Saito Keiji , Tanaka Motoharu
Published: July 2006

The kinetics of reactions of meso-tetra(4-pyridyl)porphine (H2TPyP) with cobalt(II) acetate and cobalt(II) nitrate was studied in acetic acid spectrophotometrically. The rate of cobalt incorporation into H2TPyP is first-order in H2TPyP. The conditional first-order rate constants are expressed as follows: for the cobalt(II) acetate system k0(Co)=K[Co(OAc)2]0(1+K[Co(OAc)2]0)−1(k1+k2[Co(OAc)2]0), where at 25 °C K=(5.5±2.0)×104 kg mol−1 (ΔH=−36±15 kJ mol−1, ΔS=−30±30 J mol−1 K−1), k1=(6.3±0.5)×10−5 s−1 (ΔH\eweq=89±8 kJ mol−1, ΔS\eweq=−27±15 J mol−1 K−1), and k2=(1.17±0.05)×10−1 kg mol−1 s−1 (ΔH\eweq=75±3 kJ mol−1, ΔS\eweq=−11±8 J mol−1 K−1); for the cobalt nitrate system k0(Co)=K1[Co(NO3)2]0(1+K1[Co(NO3)2]0)−1(k1+k2[Co(NO3)2]0+k3K2[Co(NO3)2]02), where at 25 °C k1=(5.1±0.5)×10−5 s−1, k2=(2.0±0.1)×10−1 kg mol−1 s−1, K1=(7.2±2.0)×104 kg mol−1, and k3K2=(1.6±0.15)×102 kg2 mol−2 s−1. Formation constants of sitting-atop complexes were determined dynamically. Mechanisms are proposed for metal ion incorporation and some discussions are made on the difference in the reactivities of acetate and nitrate of cobalt(II) in acetic acid.
The Photochemistry of the Host-Guest Complex. V. The Effect of the Sodium Ion on the Photoreaction of Benzil Derivatives with a Crown Ether Moiety
Authors: Hirano Hideki , Kurumaya Katsuyuki , Tada Masaru
Published: July 2006

The photolysis of 4′-(2-phenyl-1,2-dioxoethyl)benzo-15-crown-5 in benzene containing 1-dodecanethiol gives benzaldehyde and 4′-formylbenzo-15-crown-5. The formation of the aldehydes was inhibited by the sodium ion, whereas the photolysis of 1-(3,4-dimethoxyphenyl)-2-phenylethanedione was not inhibited by the sodium ion. This inhibition must be due to the decrease in the formation of benzoyl radicals from the triplet excited state of the crown ether derivative. The salt effect was discussed on the basis of the spectral data.
Synthesis of Oligoinosinates with 2′–5′ Internucleotide Linkage in Aqueous Solution Using Pb2+ Ion
Authors: Sawai Hiroaki , Ohno Masaji
Published: July 2006

Oligoinosinates up to a pentamer were synthesized by the polymerization of inosine-5′-phosphorimidazolide in aqueous solution using Pb2+ ion. 2′–5′ Internucleotide linkage was preferentially formed. The yields of the 2′–5′ linked dimer, trimer, and tetramer were 14.8, 4.5, and 1.6%, respectively. A small amount of linkage isomers of oligoinosinates with 3′–5′ linkage was obtained. The products were characterized by sequential enzyme tests.
Effects of β-Cyclodextrin on Fluorescence Quenching of Sodium 1-Pyrenesulfonate by Aniline in Aqueous Media
Authors: Kobashi Harumichi , Takahashi Masatoshi , Muramatsu Yasuyoshi , Morita Toshifumi
Published: July 2006

β-Cyclodextrin added to the fluorescence quenching system of the title compounds has two effect, depression on dynamic quenching and binding between the fluorescer and quencher causing rapid quenching.
The Photochemical Reaction of Benzo[c]cinnoline. IV. Comments on the Mechanism of 2,2′-Diaminobiphenyl Formation
Authors: Inoue Hiroyasu , Hiroshima Yukimi , Sakai Toshihiko , Sakurai Tadamitsu , Fukuda Norio
Published: July 2006

In order to determine the mechanism of 2,2′-diaminobiphenyl formation from benzo[c]cinnoline, effect of aldehyde on the reaction was examined. It is proposed that ethanal, which was generated from ethanol in the initial photoreduction, formed an adduct with 5,6-dihydrobenzo[c]cinnoline, and that the resulting adduct participated in the subsequent photo-induced 2,2′-diaminobiphenyl formation.
Use of Propagators in the Hückel Model. III. Stability and Reactivity
Authors: Ohmae Takayuki , Nishikawa Kiyoshi , Deguchi Kisaburo , Aono Shigeyuki
Published: July 2006

The propagator approach is applied to the problems of chemical reactivity and stability. Subjects discussed are the ring closure and opening reactions, the Diels-Alder reaction and sigmatropic reaction for reactivity; the aromaticity, two ring compounds (such as naphthalene and azulene), and benzenoid hydrocarbons (such as anthracene and phenanthrene) for stability. Results are given in analytical formulas.
Electron Spin-Spin Interaction in Excited Triplet States of Aromatic Hydrocarbons with a Trigonal Symmetry Axis
Authors: Higuchi Jiro
Published: July 2006

Zero-field splitting (ZFS) parameters of benzene, triphenylene, and coronene molecules in their lowest and second excited triplet states are calculated from the electron spin-spin interaction using semi-empirical self-consistentfield π-electron molecular orbitals. The results show that in obtaining a good agreement of the evaluated ZFS parameters with the experimental values the selection of the basis functions in LCAO-MO’s with zero-differential overlap is actually important. The ZFS parameters in some distorted structures are also calculated.
The Formation of Amino Acids by the Reactions of Singlet NH with Several Carboxylic Acids
Authors: Tsunashima Shigeru , Kitamura Takashi , Sato Shin
Published: July 2006

The photolysis of hydrogen azide was studied in liquid acetic acid, propionic acid, and isobutyric acid at room temperature. The formation of amino acids was confirmed by the color reactions with ninhydrin and with chromotropic acid and by the NMR spectra. From the propionic acid, α- and β-alanine were formed in the ratio of 1.5. In the case of isobutyric acid, α- and β-aminoisobutyric acids were formed in the ratio of about 5. These results are explained by the insertion reaction of NH(a1Δ) into the C–H bonds of carboxylic acids.
1H NMR Studies on the Interactions of Acyclic Polyethers with Dimethyltin Bichloride in Aromatic Solvents
Authors: Otera Junzo , Shiomi Tadashi , Murakami Kazuhiko , Kawasaki Yoshikane
Published: July 2006

The interactions between various acyclic polyethers, RO(CH2CH2O)nR′(R, R′=CH3, Ph), and dimethyltin dichloride (DMTC) in aromatic solvents have been studied by means of 1H NMR spectroscopy. On the basis of a continuous variation method, the formation of the 1 : 1 complexes between glymes, CH3O(CH2CH2O)nCH3(n=2, 3, 4), and DMTC was revealed in benzene. The 2J(119Sn–CH3) values suggested distorted trans-octahedral configurations for these complexes. From the statistical consideration of stability constants, it was found that the coordination occurred virtually through neighboring two oxygen atoms in these complexes. DMTC gave the complexes of both 1 : 1 and 1 : 2 glyme/DMTC stoichiometry with glymes (n=5, 6) in benzene and with all glymes employed here in toluene and 1-chloronaphthalene. Coexistence of 1 : 1 and 1 : 2 species was also encountered for PhO(CH2CH2O)nCH3 (n=3, 4, 5), whereas no appreciable interaction was observed between PhO(CH2CH2O)nPh (n=2, 3, 4) and DMTC. On the basis of these observations, the additional formation of the 1 : 2 complexes was assumed to be caused by the bulkiness of polyethers.
Reactions of 5,6-Dilithioacenaphthene-N,N,N′,N′-Tetramethyl-1,2-ethanediamine Complex with α-Diketones. I. cis-Directing 1:1 Cyclic Additions with Acyclic and Cyclic α-Diketones and Related Compounds
Authors: Tanaka Norio , Kasai Toshiyasu
Published: July 2006

The title complex (3) is readily generated from 5,6-dibromoacenaphthene with butyllithium and the diamine in ether at −10–0 °C. The reaction of 3 with biacetyl gave cis-1,2,5,6-tetrahydro-1,2-dimethylcyclopent[fg]acenaphthylene-1,2-diol but no trans-isomer, whereas the reaction of pyracenequinone (PYQ) with methylmagne-sium bromide gave both the cis- and trans-dioh. The reactions of 3 with acenaphthenequinone and PYQ also gave cis-diols. On treatment with phenylboronic acid, these cis-diols quantitatively yielded the corresponding cyclic esters. The diols and their derivatives tend to form crystalline molecular compounds with solvent molecules. The stereoselectivity of the cyclic addition between 3 and the acyclic α-diketone can be best explained in terms of five-membered chelate-ring formation in a transition state.
Reactions of 5,6-Dilithioacenaphthene-N-N,N′,N′-Tetramethyl-1,2-ethanediamine Complex with α-Diketones. II. Competitive Oxophilic and Carbophilic Additions and Redox Reactions
Authors: Tanaka Norio , Kasai Toshiyasu
Published: July 2006

The reaction of the title complex (3) with benzil did not give the 1 : 1 cyclic addition product expected, but gave 5,6-dibenzoylacenaphthene, 5-(1-hydroxy-2-oxo-1,2-diphenylethyl)-6-(2-oxo-1,2-diphenylethoxy)acenaphthene (5), 5-benzoyl-6-(1-hydroxy-2-oxo-1,2-diphenylethyl)acenaphthene, benzoin, and benzilic acid. Compound 5 suggests a new type of oxophilic addition accompanied by a carbophilic addition. The reaction of 3 with 9,10-phenanthrenequinone in a 1 : 1 molar ratio gave both the oxidative homo-coupling product of 3, 1,2,7,8-tetrahydrodicyclopenta[cd : lm]perylene, and the hydroquinone dianion, which was converted into 9,10-diacetoxyphenanthrene on acetolysis. The differences in the reaction modes between 3 and α-diketones can basically be understood in terms of the redox potentials and the steric factors of the α-diketones.
Diisobutylaluminum 2,6-Di-t-butyl-4-methylphenoxide. Novel Stereoselective Reducing Agent for Prostaglandin Synthesis
Authors: Iguchi Sadahiko , Nakai Hisao , Hayashi Masaki , Yamamoto Hisashi , Maruoka Keiji
Published: July 2006

In an effort to explore the selective reducing agents suitable for prostaglandin synthesis, diisobutylaluminum 2,6-di-t-butyl-4-methylphenoxide (1) is found to be among the best. Reduction of the C-15 ketone with 1 in toluene at −78 °C produced the desired 15S-alcohol in 95% yield with 92% stereoselectivity. The present procedure is suitable for the synthesis of prostaglandin derivatives and related polyfunctional natural products as shown in the conversion of PGE2 methyl ester to PGF2α methyl ester in 95% yield and 100% selectivity.
NMR Studies of Picolyl-type Carbanions. V. 7Li and 13C Spectra of Picolyl-type Anions with Lithium as a Counter Ion
Authors: Konishi Kazuyori , Yoshino Akihiro , Katoh Morimatsu , Takahashi Kensuke , Kawada Yuzo , Sugawara Tadashi , Iwamura Hiizu
Published: July 2006

The 7Li and 13C NMR spectra have been observed for picolyl-type anions with lithium as a counter ion in polar solvents. With reference to the observed chemical shifts, it is concluded that these lithium salts are present in THF as tight ion pairs in which the anion-cation interaction takes place mainly at the ring nitrogen. Thus, the picolyl-type anions are characterized by their ion-pair structures.
Dissociation of Micelles and Intermicellar Concentrations of Aqueous Solutions of Calcium and Sodium Decyl Sulfates
Authors: Koshinuma Masakatsu
Published: July 2006

Activities of the surfactant ions and the counterions were calculated from the electromotive forces of concentration cell with ion-exchange membranes for the aqueous solutions of calcium (Ca(DeS)2) and sodium (NaDeS) decyl sulfates. Moreover, the mean activities and the activity coefficients were obtained. From these activities, the valence effects of the counterions on the dissolved state of micellar solutions were studied. The following results were obtained: (1) The mean activities were not constant, but increased with the increase in the concentration of the two surfactants above the CMC; the slope of curve of the mean activity for Ca(DeS)2 against its concentration was smaller than that for NaDeS. (2) The CMCs were 6.4 for Ca(DeS)2 and 32.8 mmol dm−3 for NaDeS, respectively. (3) For the mechanism of micelle formation, the phase separation model was set up in both cases. (4) From this model, the degrees of dissociation of the micelles were calculated as 0.12 for Ca(DeS)2 and 0.28 for NaDeS, respectively. (5) The intermicellar concentrations of the Ca2+, the Na+, and the decyl sulfate (DeS−) ions were calculated; those of the counterions increased but those of the DeS− ions decreased with the increase in their surfactant concentrations. Moreover, those of the DeS− for Ca(DeS)2 changed slowly while those for NaDeS changed steeply.
A Conductance Study of Alkali Metal Ion–18-Crown-6 Complexes in N,N-Dimethylformamide
Authors: Takeda Yasuyuki
Published: July 2006

The formation constants, KML+, for 1 : 1 complexes of 18-crown-6 (18C6) with alkali metal ions (Na+, K+, Rb+, and Cs+) and the limiting ionic molar conductivities, λ°, of the complexed cations in N,N-dimethylformamide have been determined conductometrically at 25 °C. The KML+ sequences of the alkali metal ions with 18C6 are K+>Rb+>Cs+>Na+. The stabilities and selectivities on complexation are governed by the solvent medium and the relative sizes of the cation and the 18C6 cavity. The λ° values of the 18C6 complexes with the alkali metal ions are all approximately equal except for Cs+, suggesting that, in the cases of Na+, K+, and Rb+, the charge of the alkali metal ion trapped in the 18C6 cavity is effectively screened by 18C6, while this is not true in the case of Cs+. The ratio of the size of the alkali metal ion to that of the 18C6 cavity appears to be an important factor in determining the magnitude of λ° for alkali metal ion-18C6 complexes.
Uncatalyzed Chemical Oscillatory Behavior in the Oxidation of Catechol with Acidic Bromate Solution
Authors: Nair Punnappillil K R , Mittal Archana , Srinivasulu Kotra
Published: July 2006

A temporal oscillatory behavior of the redox potential in the oxidation of catechol with potassium bromate in sulfuric acid medium is reported.
Unusual Transposition of the Carbonyl Group in the Reduction of 2-Amino-1-indanone
Authors: Kim Jack C
Published: July 2006

The catalytic reduction procedure of 2-amino-4,5-dimethoxy-1-indanone hydrochloride gave a major reduction product of 2-amino-4,5-dimethoxyindan hydrochloride, along with a small amount of a rearranged 4,5-dimethoxy-2-indanone. The isolated intermediate, 2-amino-4,5-dimethoxy-1-indanol hydrochloride yielded exclusively 4,5-dimethoxy-2-indanone under catalytic reaction conditions (acid treatment). The unusual transformation product was verified on the basis of IR, NMR and the result of elemental analysis. A plausible mechanism for the rearrangement is discussed.
The Splitting of the ESR Signal of Di-t-butyl Nitroxide Solubilized by Micellar Solutions
Authors: Isshiki Shojun , Uzu Yuhei
Published: July 2006

In a hexadecyltrimethylammonium bromide solution containing the stable micelle, a solubilized di-t-butyl nitroxide facilitated the partial resolution of the high-field line of the ESR spectrum, which can be associated with the radical in aqueous and micellar phases. Further analysis of the lineshape was made as a function of the surfactant concentration or the temperature.
Electrochemical Behavior of Alkoxo-bridged Binuclear Copper(II) Complexes with N,N-Dialkyl-N′-(hydroxyalky)alkanediamine
Authors: Aihara Makoto , Kubo Yoshiko , Nishida Yuzo , Kida Sigeo
Published: July 2006

The alkoxo-bridged binuclear copper(II) complexes with N,N-dialkyl-N′-(hydroxyalkyl)alkanediamine were investigated by electrochemical methods. The binuclear complexes exhibited two non-separable sequential, oneelectron steps, the half-wave potentials of which were almost identical, in N,N-dimethylformamide. On the other hand, the complexes gave two distinctive one-electron reduction waves in acetonitrile.
Preparation of Sephadex Derivatives with Optically Active Groups and Column-chromatographic Application to the Resolution of Some Cobalt(III) Complexes
Authors: Fujita Miho , Sakano Masanobu , Yoshikawa Yuzo , Yamatera Hideo
Published: July 2006

Optically active cation-exchangers were newly prepared as Sephadex derivatives derived from l-alanine, l-valine, l-aspartic acid, and l-threonine. They were applied to the column-chromatographic resolution of some cobalt(III) complexes, partial resolution being attained.
N-Sulfonylaminyls. The Isolation of Dimers and Their Properties
Authors: Miura Yozo , Nakamura Yuji , Kinoshita Masayoshi
Published: July 2006

From the reaction mixtures of sulfonamides [3,5-(t-Bu)2C6H3NHSO2C6H4CH3-p and 3,5-(t-Bu)2C6H3NHSO2CH3] with di-t-butyl diperoxyoxalate, dimers of N-sulfonylaminyls were isolated as pure crystals which, in solution, dissociated into the corresponding N-sulfonylaminyls upon heating to 60 °C.
Ring Monofluorinated Hydroxypyrazoles
Authors: Kagaruki Serry R F , Kitazume Tomoya , Ishikawa Nobuo
Published: July 2006

3-Alkyl(or aryl)-4-fluoro-5-hydroxypyrazoles and their 1-methyl derivatives were prepared by the reaction of methyl α-fluoro-β-alkyl(or aryl)-β-keto esters with hydrazine hydrate or methylhydrazine in ethanol. The reaction of arylhydrazines with α-fluoro-β-keto esters gave only hydrazones which could not be cyclized to pyrazoles.
Removal and Recovery of Organic Pollutants from the Aquatic Environment. VII. Adsorption of Phenol and Carboxylic Acids on Crosslinked Poly(4-vinylpyridine)
Authors: Kawabata Nariyoshi , Higuchi Ichiro , Yoshida Jun-ichi
Published: July 2006

Molecular adsorptions of phenols and carboxylic acids on crosslinked poly(4-vinylpyridine) were studied in comparison with those on various polymeric adsorbents. Enthalpies for the adsorption of phenol on various polymeric adsorbents were evaluated based upon the temperature dependence of the phenol adsorption isotherms. The enthalpy on crosslinked poly(4-vinylpyridine) was close to that on porous poly(styrene-divinylbenzene) resin with no ion exchange functional group, and was much smaller than that on commercial weak base anion exchange resin. The relative adsorption capacities of various polymeric adsorbents for carboxylic acids and substituted phenols indicated that the acid-base interaction as well as hydrophobic interaction between these organic acids and crosslinked poly(4-vinylpyridine) was an important factor in the adsorption.
Magnetic Susceptibility and Crystal Structure of 1,5-Diphenyl-3-(4-chlorophenyl)verdazyl Radical
Authors: Azuma Nagao , Tsutsui Kanji , Miura Yozo , Higuchi Taiichi
Published: July 2006

The magnetic susceptibility of 1,5-diphenyl-3-(4-chlorophenyl)verdazyl (Cl-TPV) has been measured on a powder sample in the temperature region between 1.8 and 80 K. It exhibited a round maximum at 21.0 K; this temperature is the highest among those observed for verdazyl monoradicals. The susceptibility can be well described by the Heisenberg linear chain model; the estimated exchange interaction parameter is J⁄k=−16.4 K. The crystal structure of Cl-TPV has been determined by means of X-ray diffraction. The crystal is orthorhombic, with the space group of Pbca and with a=22.041(5), b=7.166(4), c=21.379(5) Å, and Z=8. The molecules are arranged in a column along the b axis. The exchange interaction has been discussed based on the crystal structure and the spin density distribution.
Asymmetric Transformation of N-Acetyl-Dl-leucine
Authors: Hongo Chikara , Yamada Shigeki , Chibata Ichiro
Published: July 2006

The asymmetric transformation of N-acetyl-Dl-leucine by a combination of preferential crystallization of a desired isomer and simultaneous racemization of the opposite isomer was studied. The reaction was analyzed in detail and a practical method for the asymmetric transformation was established. A supersaturated solution of N-Ac-Dl-Leu in acetic acid containing catalytic amounts of acetic anhydride was seeded with the crystals of N-Ac-l-Leu and cooled at a rate of 10 °C/h from 100 °C to 40 °C. As a result, almost optically pure N-Ac-l-Leu was obtained in a yield of 70%, based on the original weight of N-Ac-Dl-Leu.
Picosecond Laser Spectroscopy of Intramolecular Heteroexcimer Systems. Time-resolved Fluorescence Studies of p-(CH3)2NC6H4–(CH2)n–(9-Anthryl), p-(CH3)2NC6H4–(1-Pyrenyl) Systems and 9,9′-Bianthryl
Authors: Migita Masahito , Okada Tadashi , Mataga Noboru , Sakata Yoshiteru , Misumi Soichi , Nakashima Nobuaki , Yoshihara Keitaro
Published: July 2006

In order to elucidate the details of elementary processes of photochemical charge transfer and heteroexcimer formation processes, and also in order to compare the obtained results with those of transient absorption spectral measurements, we have examined the following intramolecular heteroexcimer systems by means of ps time-resolved fluorescence measurements with a mode-locked Nd3+: YAG laser and a streak camera: p-(CH3)2–NC6H4–(CH2)n–(9-anthryl) (n=0, 1, 2, 3), p-(CH3)2NC6H4–(CH2)n-(1-pyrenyl) (n=1, 2, 3) and 9,9′-bianthryl. Effects of methylene chain length, solvent polarity and viscosity upon the intramolecular charge transfer processes have been clearly demonstrated. It is concluded that molecules with sandwich configuration in the ground state are not recognized in both n=3 compounds, and it takes a few ns for the heteroexcimer formation in hexane because of an extensive conformation change necessary to take sandwich configuration. Both conformation change and solvent reorientation are involved in the heteroexcimer formation processes in polar solvents, and heteroexcimer formation becomes faster with increase of solvent polarity and decrease of its viscosity. Moreover, two step conformation changes are observed in the case of the heteroexcimer formation of n=3 compounds in polar solvents, i.e. a heteroexcimer with loose structure is formed first, and then follows a structural change to the one of sandwich type. In acetonitrile, a strongly polar solvent, formation of heteroexcimer is very fast, occurring within the time-resolution of the picosecond apparatus.
Transmission of Low-energy Electrons (0–15 eV) through Thin Films of Ethers, Ketones, Alcohols, and Ice. Determination of the Quasifree Electron State Energy
Authors: Hiraoka Kenzo , Nara Masaji
Published: July 2006

The transmission of low-energy electrons (0–15 eV) through 10–100 Å films of ethers, ketones, alcohols, and ice has been studied. Structures are indicated by electron current It transmitted through a thin film as a function of the incident electron energy Vi, displayed as dIt⁄dVi  vs.  Vi. With increasing the film thickness, a decrease of the height of the first peak (due to injection of electrons in the film) and an appearance of a second peak are observed for ethers and alcohols. The energies of quasifree electron state V0 are determined by measuring the energy of the second peak from the first peak for solid diethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 1-pentanol, 1-hexanol, and 1-nonanol. For acetone, diethyl ketone, dimethyl sulfoxide, and ice, neither a decrease of the first peak nor an appearance of a second peak is observed, indicating that these compounds have negative V0 values. From the energy of the onsets of broad negative peaks appeared at ≈14 eV for ethers and alcohols, the solid phase ionization energies IS and the polarization energies of cations P+ by the solid media are determined.
Metal Complexes Coordinating Pyridine Derivatives. II. Circular Dichroism and Magnetic Circular Dichroism Spectra of Chromium(III) Complexes in the Region of Pyridine Ring Absorption Band
Authors: Yamamoto Yukihiro , Shimura Yoichi
Published: July 2006

Dianionochromium(III) complexes coordinating (S)-N,N′-bis(2-pyridylmethyl)propylenediamine (abbrev. S-picpn) or (S)-1-(2-pyridyl)ethylamine (abbrev. S-pea) show CD spectra of a dispersion type in the region of pyridine ring absorption band. Utilizing the data of X-ray crystal structure analysis of Δ-cis-α-[CrCl2(S-picpn)]Cl, the difluoro complex shows the correct exciton CD sign pattern expected from a simple theory but the dichloro and dibromo complexes the inverse sign pattern. The latter fact is explained in terms of overlapping of the pyridine ring absorption band with the halogeno-to-chromium charge transfer band, referring to MCD spectra. The absorption and MCD bands appeared in the region 30–35×103 cm−1 for all the chromium(III) complexes are assigned to the spin-forbidden π→π* transition of the coordinated pyridine group.
Kinetics of Monomerization or Polymerization Reaction for Bis(N-phenylsalicylideneaminato)nickel(II) and Bis(N-methylsalicylidene-aminato)nickel(II) in Solid Phase
Authors: Miyokawa Kikuo , Hirashima Hidenori , Masuda Isao
Published: July 2006

A kinetic investigation was carried out by means of a thermomagnetic analysis on two structural transformation reactions in solid phase: monomeric square planar-to-polymeric octahedral for Ni(N-Me-salam)2 and polymeric octahedral-to-monomeric square planar for Ni(N-Ph-salam)2. The polymerization process followed the Avrami-Erofeev equation (n=2) with Ea=303 kJ/mol and the monomerization followed the first order equation with Ea=78 kJ/mol. The thermal pyridine liberating reaction of Ni(N-Ph-salam)2py2, involving an octahedral-to-square planar transformation, has been investigated isothermally and found to follow the first order equation with Ea=167 kJ/mol.
Syntheses and Properties of α-Ethyl-substituted Bisdehydro[15]annulenones
Authors: Ojima J\={u}ro , Murosawa Yoshiko
Published: July 2006

2-Ethyl-5,10-dimethyl- and 15-ethyl-5,10-dimethyl-6,8-bisdehydro[15]annulenone were synthesized. Influence of α-ethyl substitution upon the skeleton of the bisdehydro[15]annulenone ring system is discussed on the basis of 1H NMR and UV spectra of these annulenones and their α-methyl-substituted derivatives.
Intramolecular [2+2]Photocycloaddition of the 3-(3-Butenyloxy)-2-cyclohexenone System
Authors: Umehara Takashi , Inouye Yoshinobu , Kakisawa Hiroshi
Published: July 2006

The irradiation of 5,5-dimethyl-3-(4-methyl-3-pentenyloxy)-2-cyclohexenone gave regioselectively, 6,6,10,10-tetramethyl-2-oxatricyclo[5.4.0.01,5]undecan-8-one, while, that of 5,5-dimethyl-3-[(3-methylcyclohexenyl)methoxy]-2-cyclohexenone afforded, regio- and stereoselectively, 1,5,5-trimethyl-8-oxatetracyclo[8.3.1.02,7.01,5]tetradecan-3-one.
The Synthesis of Antigenic Glycopeptides, 2-Acetamido-N-(β-l-aspartyl)-2-deoxy-4-O-β-(d-galactopyranosyl)-β-d-glucopyranosylamine. (N-Acetyllactosaminyl-l-asparagine)
Authors: Shaban Mohammed Abd El-Monem , Jeanloz Roger W
Published: July 2006

The title compound, serving as intermediate in the chemical and biochemical synthesis of glycopeptides and as a reference substance in the structure elucidation of glycoproteins, was synthesized. 2-Acetamido-4-O-allyl-3,6-di-O-benzyl-2-deoxy-β-d-glucopyranosyl azide was reduced to the corresponding β-d-glucosylamine and coupled with 1-benzyl N-benzyloxycarbonyl-l-aspartate to give 2-acetamido-4-O-allyl-3,6-di-O-benzyl-N-[(S)-3-benzyloxycarbonyl-3-benzyloxycarbonylamino)propionyl]-2-deoxy-β-d-glucopyranosylamine. Removal of the allyl group of the latter followed by condensation with 2,3,4,6-tetra-O-acetyl-α-d-galactopyranosyl bromide gave the fully protected N-acetyllactosaminyl-l-asparagine. De-blocking of the O-acetyl, benzyl, and benzyloxycarbonyl groups gave the title compound.
Metal Complexes of Amino Acids. XIV. Carbon-13 NMR of Cobalt(III) Complexes Containing N-Substituted Glycines
Authors: Ama Tomoharu , Kawagughi Hiroshi , Yasui Takaji
Published: July 2006

The down-field shifts of α-carbons in N-alkylglycines, which were caused by the chelation to cobalt(III), were larger than those in C-alkylglycines. The down-field shifts of N-(carboxymethyl)glycine (ida) and N-(2-aminoethyl)glycine (enma) in fac complexes were also larger than those of ida and enma in mer complexes, respectively, and those of the C-alkylglycines.
The Aromatization Observed on the Reaction of Terpinolene with Tetrahydrogeraniol in the Presence of Boron Trifluoride Etherate
Authors: Nagai Kimiko , Nakayama Mitsuru
Published: July 2006

The reaction of terpinolene with tetrahydrogeraniol in the presence of boron trifluoride etherate gave an aromatic ether in addition to the corresponding aliphatic ether, along with p-cymene, p-cymen-8-ol, and the monoterpene hydrocarbons formed by double-bond migration. The aromatic ether was proved to form upon the treatment of the aliphatic ether with boron trifluoride etherate.
Synthetic Photochemistry. XXIII. The Photoreduction of Dioxetanes to cis-1,2-Glycols: 18O-Labellingr Experiments
Authors: Takeshita Hitoshi , Hatsui Toshihide
Published: July 2006

The Rose Bengal-sensitized photooxidation of some dioxetane-forming olefins, the Diels-Alder dimer of spiroheptadiene, indene, acenaphthylene, and thujopsene, under an 18O2-atmosphere yielded the labelled analogs of the previously characterized cis-1,2-glycols. According to the mass-spectral analysis, both oxygens of the glycols were derived from the oxygen molecule.
Ultrasonic Absorption in Solutions of Sodium Iodide in Isopropyl Alcohol and Isopropyl Alcohol–Water Mixtures
Authors: Okuwa Tsunemichi , Ohno Kozo
Published: July 2006

Ultrasonic relaxational absorption was observed in solutions of NaI in i-PrOH. Assuming the excess ultrasonic absorption to be caused by the relaxation of the dissociation equilibrium of NaI in the solutions, the dissociation and recombination rates of NaI, the Arrhenius activation energy, and the enthalpy and volume changes due to dissociation were calculated; these were compared with the values estimated from other methods. An increase of the dissociation constant of NaI was observed with an increase in the concentration of H2O in i-PrOH–H2O mixtures.
Studies on the Electronic Structures of Hydrocarbon Diradicals by the Unrestricted Hartree-Fock Theory
Authors: Hashimoto Katsufumi , Fukutome Hideo
Published: July 2006

Electronic structures of low-lying states of cyclobutadiene, trimethylenemethane (2), and tetramethyleneethane (3) are studied by the unrestricted Hartree-Fock (UHF) theory. Characteristics of electronic correlations, called dynamical spin polarization effect, in these molecules are well described by corresponding orbitals and spin density structures of low-lying UHF solutions. The spin polarization of σ electrons is found to be relatively small but not negligible for quantitative discussion. The two low-lying singlet states of 2 are described by two UHF solutions with different spin density structures. The fact that the singlet UHF state of 3 lies a little below the triplet UHF state is explained by the difference in the spin polarization of the bonding π electrons between the singlet and triplet states. Two rules are given which predict the spin structure of low-lying UHF states and the spin multiplicity of ground states of hydrocarbon diradicals. These rules are applied to 1,1,2,3,3-pentamethylenepropane and 1,3-dimethylenecyclobutadiene, which confirms their validity.
Kinetics and Mechanism of Acylhydrazine Hydrolysis in Sulfuric Acid–Water Mixtures
Authors: Mashima Mitsuo , Ikeda Fujiko , Doi Takako , Nishikawa Sadakatsu
Published: July 2006

The rates of acid-catalyzed hydrolysis of formylhydrazine, acetylhydrazine, chloroacetylhydrazine, propionylhydrazine, butyrylhydrazine, and octanoylhydrazine in sulfuric acid–water mixtures have been investigated over a wide range of acidities (about 1–18 M H2SO4) by means of spectrophotometric methods. First-order kinetics were obtained in all cases, and the pseudo-first-order rate constants showed one of two types of acidity dependences: (i) a rate maximum at intermediate acidities, followed by slow hydrolysis in highly concentrated acids; (ii) a rate maximum at intermediate acidities, followed by a sharp increase in rate at high acidities. This result was treated as a function of the Hammett acidity function, the water activity, and the total concentration of hydrogen ion to yield reaction parameters which are explicable in terms of a change in mechanism at a high acidity from A-2 to A-1. The mechanism change also was deduced from a criterion based on the values of activation entropies.
Solid-Liquid and Liquid-Liquid Phase Equilibria in the Symmetrical Tetraalkylammonium Halide–Water Systems
Authors: Nakayama Haruo
Published: July 2006

Solid-liquid and liquid-liquid phase diagrams of the binary R4NX–water (R=n-C3H7–n-C6H13 and i-C5H11; X=F, Cl, Br, and I) systems were determined in the temperature range between −20 °C and +80 °C. These diagrams showed (1) the formation of a clathrate-like hydrate for four salts (n-C5H11)4NF, (n-C5H11)4NCl, (i-C5H11)4NBr, and (i-C5H11)4NI; (2) a phase separation into two liquid phases in the systems of (n-C5H11)4NBr, (i-C5H11)4NBr, (n-C6H13)4NCl, and (n-C6H13)4NBr; (3) that the solubility (in water at a definite temperature) of a series of the salts did not show a systematic change with respect to either the alkyl-chain length or the kind of anion; and (4) that the salt which gave the maximum solubility in water at 25 °C was (n-C5H11)4NCl for chloride, (n-C4H9)4NBr for bromide, and (C2H5)4NI for iodide, respectively. The effect of anions on the solubilities of a series of salts having the same cation was examined. It was found that the ratio mcl⁄mI at 25 °C became as high as 22800 for the tetrapentylammonium salts. Phase diagrams for the bolaform salt [(n-C4H9)3N(CH2)6N(nC4H9)3]X2–water systems are also presented.
Solubility Diagrams of Cobalt(III) Complexes Containing Amino Acid. I. Spontaneous Resolution of Tetraammine-(valinato or leueinato)cobalt(III) Salts
Authors: Yamanari Kazuaki , Naito Shigeru , Shimura Yoichi
Published: July 2006

The binary and ternary solubility phase diagrams of the racemic and optically active complexes, [Co(val)(NH3)4]X2 and [Co(leu)(NH3)4]X2 (X=(1/2)SO42−, Cl−, Br−, and I−), were determined in water. Spontaneous resolution was found for [Co(Dl-val)(NH3)4]X2 (X=Cl− and Br−) at 5–55 °C and for [Co(Dl-leu)(NH3)4]SO4 at 30–55 °C, the latter of which has been shown to crystallize as both a racemic compound (below 30 °C) and a conglomerate (above 30 °C).
The Interaction between α-Helical Poly-l-lysine and Thyroxine as Measured by Circular Dichroism
Authors: Okabe Nobuo , Okamura Mariko , Tokuoka Ryoji , Tomita Ken-ichi
Published: July 2006

The interaction between α-helical poly-l-lysine (poly(l-Lys)) and the thyroid hormone, l-thyroxine (l-T4), was investigated at pH 11 by means of circular dichroism (CD) measurements in the wavelength region of 200–380 nm. At least four CD bands were induced near 235, 250, 290, and 343 nm. This indicates that these induced Cotton effects occurred as the result of the binding of l-T4 to poly(l-Lys), probably due to the electrostatic interaction. The wavelengths of the induced GD bands corresponded to those of the UV absorption bands of l-T4 in the poly(l-Lys) : l-T4 mixture, although small red-shifts of the CD bands were observed at the shortest and the longest wavelengths (235 nm and 343 nm). These CD bands might be interpreted by the fixed intramolecular orientation around an asymmetric α-carbon atom of the bound l-T4 or by the intermolecular interaction between the peptide backbone of poly(l-Lys) and the bound l-T4.
Syntheses of Recyclized Macrolide Antibiotics and Related Derivatives from Mycaminosyltylonolide
Authors: Tanaka Akihiro , Watanabe Azuma , Kobayashi Reiko , Tsuchiya Tsutomu , Umezawa Sumio
Published: July 2006

Mycaminosyltylonolide diethyl acetal was, after reduction of the 9-keto group, hydrolyzed, and the seco-acids obtained were recyclized to give new 16-membered (9R)- and (9S)-hydroxy macrolide derivatives, in which the 23-hydroxyl group of the starting substance was incorporated into the macrolactone ring. Selective oxidation of the (9S)-hydroxy derivative (15) with DDQ gave the keto compound (18). Removal of the acetal-protecting groups gave a new macrolide (19), which is antibacterial. Several other O-acetyl derivatives were also prepared and their antibacterial activities were measured. By the 1H- and 13C-NMR spectroscopies of 3,23-di-O-acetylmycaminosyltylonolide diethyl acetal by varying the temperature, the presence of two rotamers was clarified.
Studies on the Behavior of Natural Surfactant at the Oil-Water Interface. II. Behavior of Natural Surfactant at the Oil-Water Interface
Authors: Ogino Keizo , Yamauchi Hitoshi , Ueno Yoshinori
Published: July 2006

The behavior of natural surfactants was studied at an oil-water interface by measurement of the interfacial tension and the observation of the oil-water interface. Lecithin was used as an oil-soluble substance and sodium cholate was used as a water-soluble substance; n-paraffin, corn oil, unsaturated fatty acid and fatty alcohol were used as an oil phase. The reduction of interfacial tension was greatest in a dodecane-sodium cholate solution system, but the minimum interfacial tension was observed in an oleic acid-sodium cholate solution system. Spontaneous emulsification occurred in the oil phase when oleic acid was left in contact with sodium cholate solution. The most remarkable change was found in the system of oleic acid in contact with sodium cholate solution, in which crystal of cholic acid were formed at the interface.
An Optical Absorption Study of Trapped Electrons in γ-Irradiated 3-Methylhexane-2,2,4-Trimethylpentane-2,2-Dimethylbutane Mixture Glasses at 77 K
Authors: Kimura Toyoaki , Ogawa Naoyuki , Fueki Kenji
Published: July 2006

An optical absorption study was made on trapped electrons in γ-irradiated 3-methylhexane-2,2,4-trimethylpentane-2,2-dimethylbutane glasses at 77 K. The absorption maximum of trapped electron spectra shifts to longer wavelengths and the trapped electron yield decreases with decreasing 3-methylhexane concentration. The observed spectral shifts were interpreted through a semicontinuum model calculation.
Metachromatic Absorption Spectra of Spin-labeled Mono- and Diamino-acridine Dyes Bound to Synthetic Polyelectrolytes
Authors: Yamaoka Kiwamu , Matsuda Takumi , Murakami Tsuyoshi
Published: July 2006

Interactions between nitroxide spin-labeled dyes (Acridine Orange, Proflavine, and 9-aminoacridinium chloride) and poly(p-styrenesulfonate), polyphosphate, and polyacrylate were studied by measuring visible absorption spectra in aqueous solutions. The bound-dye spectra and equilibrium constants were determined by the principal-component-analysis method. The metachromatic behavior of dye-polymer complexes was clarified.
Acid-induced Ring-opening of 2′-Substituted Spiro[anthracene-9(10H), 1′-cyclopropan]-10-ones
Authors: Hirakawa Kiyoichi , Sato Hajime
Published: July 2006

The title compounds (1) reacted under acidic conditions to give cyclopropane ring-opened products. In these reactions of 1 bearing methyl-, phenyl-, chloro-, bromo-, and acetoxy-substituents, the cyclopropane ring opened from the more substituted side.
The Formation of a Propellane by the Oxidation of Biphenylene with Manganese(III) Acetate
Authors: Kurosawa Kazu , McOmie John F W
Published: July 2006

The reaction of biphenylene with manganese (III) acetate gave 2-acetoxybiphenylene, 2-formylbiphenylene, 2-(acetoxymethyl)biphenylene, and 7-oxa-10,11-benzotricyclo[4.3.2.0]undeca-2,4,10-trien-8-one. The reaction pathways are discussed.
Synthesis of Amphiphilic Porphyrins
Authors: Takagi Shigeru , Yamamura Takeshi , Nakajima Masayuki , Ishiguro Koji , Kawanishi Yuji , Nihojima Shigeru , Tsuchiya Hiroo , Saito Taro , Sasaki Yukiyoshi
Published: July 2006

A water soluble surfactant porphyrin 5,10,-15-tris (1-methylpyridinium-4-yl)-20-[4-(octadecyloxy)phenyl]21H, 23H-porphine triiodide and its metal complexes have been synthesized and characterized.
Ring-opening Polymerization of Tetrahydrofuran Initiated by the 2-Norbornyl Cation Generated from exo-2-Norbornyl Tosylate in the Presence of Lithium Perchlorate
Authors: Takeuchi Ken’ichi , Kato Yukari , Okamoto Kunio
Published: July 2006

exo-2-Norbornyl tosylate initiates ringopening polymerization of THF in the presence of lithium perchlorate. The deuterium scrambling of exo-2-norbornyl exo-3-d tosylate indicates the SNl nature of the initiation mechanism.
Sand Separated from Athabasca Tar Sand (Canada) by Solvent Extraction
Authors: Yoshida Ryoichi , Okutani Takeshi , Shimokawa Katsuyoshi , Ikawa Yasuko , Maekawa Yousuke , Kodaira Kohei , Yoshida Yuji
Published: July 2006

The nature of the sand separated from Athabasca tar sand (Canada) by solvent extraction was examined. The existence of α-SiO2 was confirmed by X-ray analysis. By DTA-TG determination, the occurrence of displacive transformation from low quartz to high quartz at 573±1 °C was proved, this coincides with the results obtained by means of X-ray analysis.
Liposomal Membranes. IX. Fluorescence Depolarization Studies on N-Dansylhexadecylamine in Liposomal Bilayers
Authors: Iwamoto Kiyoshi , Sunamoto Junzo
Published: July 2006

A fluorescent probe, N-dansylhexadecylamine (DSHA), was found to aggregate in aqueous media by monitoring the emission maximum, relative intensity, and polarization of fluorescence as functions of solvent polarity and probe concentration. In aqueous methanol, the critical solvent polarity for DSHA at a given concentration to form self-aggregates corresponded to 57% (v/v) aqueous methanol, while the critical aggregate concentration for the probe was 2.3×10−6 M in 50% aqueous methanol. In liposomal bilayers, the dansyl moiety seemed to be localized in a polar region close to the surface of membranes. Fluorescence characteristics of DSHA in liposomes as a function of incubation temperature revealed the phase transition of liposomal bilayers, which was almost consistent with those previously estimated by other methods. As the salt concentration was increased up to about 1.5 M, DSHA in liposomes underwent the phase separation and formed self-aggregates even in liposomal bilayers.
Studies on Mixed Chelates. XII. Formation and Electronic Spectra of 5-Coordinated Mixed Copper(II) Chelates Containing N-Alkylated Ethylenediamine, Acetylacetonate, and Pseudohalide Anions
Authors: Fukuda Yutaka , Sato Noriko , Hoshino Naomi , Sone Kozo
Published: July 2006

The visible absorption spectra of three new mixed chelates of copper (II), Cu(tmen)(acac)X(tmen=N,N,N′,N′-tetramethylethylenediamine, acac=acetylacetonate ion, X=NCS, N3, or NCO) were studied in various organic solvents. It was found that the \ ildeνmax values of their d-d bands depend strongly on the nature of the solvent, and shift in the opposite direction as compared with the case of [Cu(tmen)(acac)]ClO4 studied before, where \ ildeνmax shifted to red with the increase of the donor number (DN) of the solvent. Here the magnitude of the red shift is affected not only by the DN, but also by other parameters of the solvent polarity, such as Kosower’s Z or Reichardt’s ET. The obtained data can reasonably be explained, if an equilibrium

[Cu(tmen) (acac)X]\ightleftarrows[Cu(tmen)(acac)]++X−

(5−coordinated)(4−coordinated)

(with axial solvation)

is assumed to exist in such solutions.
Bridges in Polynuclear Complexes. II. An X-Ray Investigation of the Coordination of Silver Ion to the μ-Peroxo Bridge of a Dinuclear Cobalt(III) Complex
Authors: Shibahara Takashi , Mori Masayasu , Matsumoto Keiji , Ooi Shun’ichiro
Published: July 2006

The crystal structure of [(en)2Co(NH2)(O2)Co(en)2](NO3)3·15/8(AgNO3)·H2O has been determined from X-ray diffraction data collected by the counter method. The crystal is monoclinic with the space group C2/c and with a=8.710(3), b=16.413(5), c=20.024(8)Å, β=90.30(4)°, and Z=4. The structure was refined by the block-diagonal least-squares method to R=0.107 for 2157 independent reflections. It has been elucidated that the Ag atom is bound to each of the two peroxo oxygen atoms with the Ag–O bond length of 2.27(1) Å. Each Ag atom is also surrounded by two more oxygen atoms belonging to the nitrate anions and these Ag–O bond lengths are 2.45(2) and 2.50(2) Å. The central five-membered ring has a symmetric envelope conformation, with the peroxo O atom deviating from the Co, N, Co plane, by 0.38 Å. The crystals contain an equal amounts of the enantiomeric forms (δδΛδδδ) and (λλΔλΔλλ). The formation constant of Ag+ and [(en)2Co(NH2)(O2)Co(en)2]3+ in aqueous solution was found to be less than 0.5.
Isobaric Thermogravimetry of the Gas Encapsulation with Molecular Sieves A
Authors: Takaishi Tetsuo , Kamei Yujiro , Yusa Atsushi , Ohgushi Tatsuo
Published: July 2006

The isobaric gas sorption with (Na,Ca)–A and (K,Ca)–A zeolites was measured gravimetrically in temperature ranges of −160–−40 °C for O2 and N2, and of room temperature—200 °C for n-C4H10. The sorption hysteresis, i.e., the gas encapsulation was observed. The maximum point, in the temperature rising branch of the isobar, was located at about −90 °C for N2 and in the range 120–170 °C for n-C4H10, and shifted to the lower temperature side with the increasing content of calcium for n-C4H10. The observed results are explained in terms of an incomplete blocking action of cations on window sites. This incompleteness was amplified by bivalent cations introduced onto other sites than the window sites, and the sieving character of the ion-exchanged zeolite was delicately modified.
The Reduction of Sulfuric Acid by Hydrogen on Various Metal–Carbon Catalysts
Authors: Katagiri Akira , Watanabe Kiyoshi , Yoshizawa Shiro
Published: July 2006

The reduction of sulfuric acid, which is formed on the activated carbon catalyst in the course of removing sulfur dioxide from exhaust gas, was investigated. The platinum, palladium, silver, and copper on activated carbon were found to be catalytically active in the reduction of sulfuric acid by hydrogen, while manganese, iron, cobalt, nickel, and zinc were found to be inactive. The copper–carbon catalyst is favorable, because sulfuric acid was reduced selectively to sulfur dioxide on it at temperatures from 190 °C to 270 °C. On the platinum–carbon catalyst, the reduction occurred at a relatively low temperature (140 °C to 200 °C), but hydrogen sulfide and elemental sulfur were formed in addition to sulfur dioxide. It is concluded from thermodynamic calculations that catalytically active metals were in the metallic state on activated carbon under the present reaction conditions. An electrochemical mechanism is proposed for the reaction.