bluuebunny/crossref_metadata_2025 huggingface dataset:
Electronic Absorption Spectra and Geometry of Molecular Ions Generated from Stilbene and Related Compounds. II. Radical Ions of (E)-Stilbene and Related Compounds
Authors: Suzuki Hiroshi , Koyano Kinko , Shida Tadamasa , Kira Akira
Published: July 2006

The electronic absorption spectra of radical ions produced by γ-ray irradiation of (E)-stilbene and related compounds in frozen matrices were measured. On illumination and on controlled warming, the spectra of the radical ions of sterically uncrowded stilbenes and diphenylacetylene remained almost unchanged, while those of the radical ions of sterically crowded stilbenes changed noticeably. Examination of the spectra and of their changes led to the following conclusions: (a) The relaxed geometry of the radical ions of sterically uncrowded stilbenes is planar or nearly planar; (b) in the unrelaxed geometries of the radical ions of (E)-α,β-dialkylstilbenes the torsion angles of the Ph–C bonds are nearly as large as in the parent molecules, and on relaxation these angles become smaller and the torsion angle of the central ethylenic bond deviates from 0° to a considerable extent; (c) for the radical ions of ortho-substituted (E)-stilbenes the geometrical change on relaxation is comparatively small.
Cyclic Orbital Interaction and Orbital Phase in Acyclic Conjugation
Authors: Inagaki Satoshi , Kawata Hirofumi , Hirabayashi Yoshio
Published: July 2006

The orbital phase continuity-discontinuity property is shown to control electron delocalization and polarization even in open chain conjugated molecules. Its chemical consequences are discussed.
Catalytic Activity of Planar Copper(II) Complexes for the Chemiluminescence of Luminol
Authors: Oishi Naoyasu , Takeuchi Masataka , Nishida Yuzo , Kida Sigeo
Published: July 2006

Some planar binuclear copper(II) complexes showed high catalytic activity for the chemiluminescence of luminol in the presence of hydrogen peroxide compared with those of mononuclear planar copper(II) complexes. The formation of singlet O2 in the reaction mixture of a binuclear copper(II) complex and hydrogen peroxide was assumed to play a key role in the catalytic function of the binuclear copper(II) complexes for the luminol chemiluminescence.
Metal Complexes of Peptides. III. The Preparation and Properties of Diammine(oligopeptidato)cobalt(III) Complexes
Authors: Kawaguchi Hiroshi , Ishii Mari , Ama Tomoharu , Yasui Takaji
Published: July 2006

Complexes of the [Co(tripeptidato)(NH3)2] and NH4[Co(tetrapeptidato)(NH3)2] types (tripeptidato and tetrapeptidato denote the tri- and tetraanions of the coordinating peptides respectively) have been prepared and characterized by means of their electronic, 1H NMR, and circular dichroism (CD) spectral data. In the NH4[Co(tetrapeptidato) (NH3)2] complex, the pep tide coordinates to cobalt(III) as a quadridentate ligand through the nitrogens of an amino and three amide groups. The additivity of the vicinal CD spectra has been found to hold for the complexes of a series of tripeptides containing l-alanine and/or glycine residue. These tri- and tetrapeptidato complexes in water easily undergo aquation reaction, releasing the ammonia molecule.
An Analysis of the Chemical Compositions of Groundwaters Utilizing a Leaching Technique. An Application to the Rokko Mountains and Their Surroundings
Authors: Tamari Yuzo , Inoue Yukiharu , Tsuji Haruo , Kusaka Yuzuru
Published: July 2006

The chemical composition of groundwaters from granitic alluvial plains is different from that from the clayey “Kobe-group” strata surrounding the Rokko mountains. The former groundwaters are dominantly rich in Ca and HCO3, while the latter are rich in Na and HCO3. In order to investigate the difference in the groundwater compositions, a chemical leaching technique was applied to samples of soils, well-sediments, and rocks collected from the Rokko mountains and their surroundings. Three leaching solutions used were as follows. CO2− saturated water to investigate the effect of chemical weathering; a 0.1 M HNO3 solution to remove hydroxide, sulfide, and colloidal matters; and a 1 M CH3COONH4 solution to leach exchangeable ions from the samples. In the leaching, leachable amounts of Na, K, Ca, and Mg as the major species and Fe and Mn as the minor species in groundwaters were determined. From the results of leaching and adsorption experiments for cations, and from a comparison of the analytical values of the cations in groundwaters with the data of the leaching experiments on the key diagram, the association of the chemical species dissolved in groundwaters with the geological characters was analysed.
Studies of Hydrous Tin(IV) Oxide Ion-exchangers. I. A Method for Synthesis and Some Properties
Authors: Inoue Yasushi , Yamazaki Hiromichi
Published: July 2006

A comprehensive study of the preparation of hydrous tin(IV) oxide ion-exchangers was made by using eight systems: (1)Na2[Sn(OH)6]–H2SO4, (2)Na2[Sn(OH)6]–H2SO4(boiling), (3)Na2[Sn(OH)6]–HCl, (4)Na2[Sn(OH)6]–CH3COOH, (5)SnCl4–NaOH, (6)SnCl4–NH3aq, (7)SnCl4–NH3aq(boiling), and (8)SnCl4-pyrohydrolysis. From a detailed examination of the dependency of the yield, the ion-exchange behavior toward Na+ and Cl− ions, the composition, and some other properties on the conditions for precipitation, it was found that the ion-exchange characteristics are similar among materials produced from the systems from (1) through (7) if we neglect some aging effect of boiling, while the difficulty of synthesis differs according to the systems. The materials obtained from the (8) system, however, showed titration curves different from those for the exchanges obtained from the other systems and had less cation-exchange capacity for Na+ by 20 per cent. From these results, it is concluded that the simplicity of the synthetic procedures in the most important criterion for choosing the best conditions for preparing the exchanger.
The Structure of the Cyclodextrin Complex. XV. Crystal Structure of Hexakis(2,3,6-tri-O-methyl)-α-cyclodextrin–p-Nitrophenol (1 : 1) Complex Monohydrate
Authors: Harata Kazuaki , Uekama Kaneto , Otagiri Masaki , Hirayama Fumitoshi
Published: July 2006

The crystal structure of the hexakis(2,3,6-tri-O-methyl)-α-cyclodextrin (abbreviated to methyl-α-CDx) complex with p-nitrophenol, C54H96O30·C6H5NO2·H2O, was investigated by the X-ray method. The crystal is monoclinic, the space group being P21 with Z=2; the cell dimensions are a=11.307(1), b=14.578(1), c=22.118(2) Å, and β=93.62(1)°. The structure was determined by means of the Patterson map and the trial-and-error method combined with the rigid-body least-squares technique, and refined by the block-diagonal least-squares method to the final R-value of 0.048 for 4976 reflections (sinθ⁄λ<0.54). The methyl-α-CDx molecule has the shape of a truncated hexagonal cone, into which the p-nitrophenol molecule is inserted. The phenolic hydroxyl group is located at the center of the methyl-α-CDx cavity, while the nitro group protrudes outside from the base-side of the host cone and is in contact with the adjacent methyl-α-CDx molecule. The water molecule, which is also located within the cavity, links the methyl-α-CDx and p-nitrophenol molecules by hydrogen bonds. Methyl-α-CDx molecules are stacked along the crystallographic a axis in a heat-to-tail mode to form a channel-type structure.
Synthesis and Maganetic Susceptibility of Dimeric Copper(II) Acetate Adducts with Triphenylphosphine or Triphenylphosphine Oxide
Authors: Tokii Tadashi , Ikeda Toyoaki , Muto Yoneichiro
Published: July 2006

Two compounds of stoichiometry Cu(CH3COO)2·L (L=triphenylphosphine or triphenylphosphine oxide) were prepared. These compounds display the antiferromagnetic behavior typical of dimeric copper(II) carboxylates. The singlet-triplet splitting energy is 371 cm−1 for the phosphine adduct and 319 cm−1 for the phosphine oxide adduct.
Preparation and Characterization of Triammine Cobalt(III) Complexes with (R)-2-(Carboxymethylthio)propionate and Its Derivative
Authors: Suzuki Masutaro , Okamoto Ken-ichi , Einaga Hisahiko , Hidaka Jinsai
Published: July 2006

Two complexes of fac(NH3)-[Co(L)(NH3)3]+ type (where L denotes (R)-2-(carboxymethylthio)propionate and (R)-2-(2-carboxymethylthio)propionate) were newly prepared and separated into two isomers, R(S), R(C) and S(S), R(C), by column chromatography. The absolute configurations of the isomers are suggested on the basis of the 13C NMR spectra.
Synthesis of cis-Jasmone via the Retroaldol-aldol Condensation of 3-(cis-3-Hexenyl)-2-cyclopentenone in an Autoclave
Authors: Yoshida Takashi , Saito Shojiro
Published: July 2006

cis-Jasmone was efficiently synthesized from 2-cyclopentenone. The treatment of 2-cyclopentenone with sodium p-toluenesulfinate gave 3-(p-tolylsulfonyl)cyclopentanone in a 92.5% yield. The alkylation of the sulfone, after the protection of the ketone, with cis-1-bromo-3-hexene, followed by desulfonylation with 5% hydrochloric acid in tetrahydrofuran, afforded 3-(cis-3-hexenyl)-2-cyclopentenone in a good yield. The retroaldol-aldol condensation of the cyclopentenone in a stainless steel autoclave in presence of 5% sodium hydroxide yielded cis-jasmone in a 80% yield.
The Synthesis of 1,2-Diazacoronene
Authors: Tokita Sumio , Hiruta Kimihiro , Kitahara Kiyoshi , Nishi Hisao
Published: July 2006

1,2-Bis(ethoxycarbonyl)-1,2-dihydro-1,2-diazacoronene-7,8-dicarboxylic anhydride (5) was obtained from diethyl 1,2-dihydro-1,2-diazabenzo[ghi]perylene-1,2-dicarboxylate, maleic anhydride, and chloranil. Treatment of the anhydride 5 with sodium hydroxide gave 1,2-diazacoronene-7,8-dicarboxylic anhydride (7). When 7 was heated with soda lime, 1,2-diazacoronene was obtained.
Synthesis of (±)-Dihydromahubanolide Using 2-Methylthio-4-pentenoic Acid Dianion
Authors: Tanaka Kazuhiko , Terauchi Makoto , Kaji Aritsune
Published: July 2006

A new and mild method for the synthesis of (±)-dihydromahubanolide has been developed by the use of 2-methylthio-4-pentenoic acid dianion.
The Function of Magnesium(II) N,N′-Dicyclohexylamidinide Complexes as a Carbon Dioxide Carrier
Authors: Matsumura Noboru , Ohba Takayuki , Inoue Hiroo
Published: July 2006

It is found that magnesium(II) N,N′-dicyclohexylamidinide complexes are useful reagents for the fixation of carbon dioxide and the transfer of the captured carbon dioxide moiety to active methylene compounds.
Solvent Effects on the Intensities of Forbidden Bands of Molecules. Absorption Spectra of Acetone and Cyclopentanone
Authors: Nakashima Kenichi , Uchida-Kai Kuniko , Koyanagi Motohiko , Kanda Yoshiya
Published: July 2006

The near ultraviolet absorption spectra of acetone and cyclopentanone have been studied in various fluid solutions at room temperature. The intensity enhancements observed are ascribed to perturbation of dispersion forces between solute and solvent molecules. The results are parallel to those of the Ham effect in benzene. No correlation was found between the intensity increments and solvent polarities. This is at variance with the correlation that has been reported in the S1(Lb)–S0 transition spectra of pyrene and coronene.
High Pressure Organic Chemistry. V. Diels-Alder Reactions of Furan with Acrylic and Maleic Esters
Authors: Kotsuki Hiyoshizo , Nishizawa Hitoshi , Ochi Masamitsu , Matsuoka Kiyoshi
Published: July 2006

A series of Diels-Alder reactions of furan with acrylic and maleic esters has been investigated under conditions of high pressure. The approximate endo/exo ratios of the adducts with acrylic and maleic esters were 6 : 4 and 8 : 2 respectively. The observed isomer distributions are ascribed to the kinetic control.
Photoreduction of Bisviologen Compounds, Viologen–(CH2)n–Viologen, by 2-Propanol
Authors: Furue Masaoki , Nozakura Shun-ichi
Published: July 2006

In order to study the polymer effect in the photoreduction of viologen-containing polymers by 2-propanol, bisviologen compounds, V2+–(CH2)n–V2+, were subjected to photoreduction. The rates of photoreduction occur in the order n=2>3>4>5>MV2+. The structure of the photoreduced species was found to be predominantly the doubly reduced species, V+–(CH2)n–V+, in the cases of n=2 and 3, and mixtures of the doubly reduced and singly reduced species, V+–(CH2)n–V2+, in the cases of n=4 and 5. Intramolecular dimeric association of V+ units was observed for all the compounds except for n=2, where the intramolecular association was structurally inhibited. The variation of rate and structure distribution of reduced species was interpreted in terms of the local concentration effect in the photoreduction step.
Proton and Carbon-13 Nuclear Magnetic Resonance Studies of the Effects of Retinal on the Dynamic Structure and Stability of Lipid Bilayer
Authors: Inoue Yoshio , Hanafusa Yoshito , Toda Masakazu , Chûjô Riichiro
Published: July 2006

The effects of retinal and vitamin A on the dynamic structure and stability of hen egg yolk lecithin bilayers have been studied by means of carbon-13 and proton NMR spectroscopies. 13C spin-lattice relaxation and paramagnetic ion permeability studies on lecithin bilayers indicate a marked decrease in flexibility of the lipid acyl chain and a breakdown of membrane impermeableness to ion by the intercalated all-trans- and 11-cis-retinal, whereas the effect of incorporated vitamin A on the fluidity of bilayers is small and its impermeableness to ion remains effective even in the presence of higher concentration of vitamin A. The experimental results are discussed in connection with the mechanism of the permeability change in photoreceptive disk membrane.
Infrared Study of the Oxidation of 2–Propanol on TiO2
Authors: Nakajima Takashi , Miyata Hisashi , Kubokawa Yutaka
Published: July 2006

Oxidation of 2-propanol on TiO2 was studied by infrared spectroscopy as well as analysis of reaction products. Propene and acetone are formed from isopropoxide species on TiO2. Only adsorbed acetone is oxidized to carbon dioxide via carboxylate species. Propene undergoes no oxidation.
Oxidative Addition of Esters of Formic Acid and β-Lactones to Ni(0)-Complexes Involving Cleavage of the C–O Bond
Authors: Yamamoto Takakazu , Ishizu Junichi , Yamamoto Akio
Published: July 2006

Reactions of esters of formic acid, HCOOR (R=C2H5, CH2C6H5), with Ni(0)-complexes (mixtures of bis(1,5-cyclooctadiene)nickel (Ni(cod)2) and tertiary phosphines (PR′3)) lead to decarbonylation of HCOOR to afford (Ni(CO)n (PR″3)4−n and ROH. Vinyl formate gives a mixture of CH3CHO, Ni(CO)n(PR′3)4−n, C2H4, and CO2 on interaction with the Ni(0)-complexes. β-Lactones liberate CO2 on treatment with the Ni(0)-complexes. Oxidative addition of the reactants to Ni involving cleavage of the C–O bond(s) accounts for the formation of the products.
Convenient Synthesis of 2,7-Disubstituted 5H-1,3,4-Thiadiazolo[3,2-a]pyrimidin-5-ones and Related Compounds
Authors: Tsuji Tadakazu , Takenaka Keiko
Published: July 2006

2,7-Disubstituted 5H-1,3,4-thiadiazolo[3,-2-a]pyrimidin-5-ones were synthesized from the reaction of 3-amino-6-methyl-2-thiouracil with carboxylic acid or from that of thiosemicarbazide with carboxylic acid and β-keto ester in the presence of phosphorus pentaoxide and methanesulfonic acid. The synthesis of related compounds is also described.
Elementary Patterns in Protein-Nucleic Acid Interactions. III. Crystal Structure of Adenine: Phthalic Acid (3:1) Complex Hexahydrate
Authors: Takenaka Akio , Sasada Yoshio
Published: July 2006

Crystal of adenine :phthalic acid (3:1) complex hexahydrate were obtained from an aqueous solution containing equimolar amounts of adenine and N,N-phthaloyl-Dl-glutamic acid. The space group is P\bar1 with unitcell dimensions of a=14.232(2), b=16.730(2), c=7.336(1) Å, α=78.97(1), β=96.14(1), and γ=68.99(1)°. The structure was solved by the direct method and its parameters were refined by a block-diagonal least-squares technique. The two carboxyl groups of the phthalic acid are dissociated and they are hydrogen-bonded to the amino group and the protonated N(1) of the two adeninium monocations. The geometrical characteristics in adeninium monocations are explained with the electronic structures perturbed by the surroundings. A typical feature of the C–H···N hydrogen bond is observed between the adeninium cations. The third adenine molecule is neutral and disordered. A comparison of the dissociation constants of the related compounds suggests that the protonation of adenine occurs when the hydrogen bonds are formed between the carboxyl group of acidic amino acid residue in protein and the unpaired adenine base in nucleic acid.
Electric Linear Dichroism Study of Sodium Poly(p-styrenesulfonate) and Its 9-Aminoacridinium Complex in Aqueous Solutions
Authors: Matsuda Koichiro , Yamaoka Kiwamu
Published: July 2006

Electric linear dichroism (ELD) of sodium poly(p-styrenesulfonate) (NaPSS) and its 9-aminoacridinium (AA) complex at a mixing ratio of polymer residue-to-dye of 6.14 was studied in aqueous solutions at 20 °C. ELD signals were measured in the electric field strength range 0—ca. 19 kV/cm at the absorption peak wavelengths; they showed a saturating trend at extremely high fields. The average angles between the orientation axis of NaPSS and the transition moments of chromophores were estimated to be 60° at 224.5 nm and 57° at 262 nm for the side chain phenyl group and 50° at 404 nm for the bound AA by using theoretical orientation functions derived for mono- and polydisperse systems. The ELD spectra were measured at fixed field strengths; 275–215 nm for NaPSS and 440–282 nm for NaPSS–AA. The reduced dichroism of NaPSS remained nearly constant throughout the 262 nm band but steadily changed below 224 nm in the 224.5 nm band, indicating that another band exists in the far UV region. The ELD spectrum of the NaPSS–AA complex revealed that the two electronic 1La and 1Lb transition moments of the bound AA are tilted at different angles to the orientation axis of the NaPSS backbone.
The Analysis of Lanthanoid-induced 13C Shifts for Naphthylamines. Contact Shifts Induced by Gd-chelates and the Spin-delocalization Mechanism
Authors: Hirayama Masatoshi , Akutsu Kenji , Fukuzawa Kazuko
Published: July 2006

The 13C shifts of 1- and 2-naphthylamines induced by Gd(fod)3 and Gd(dpm)3 were shown to consist predominantly of a contact contribution, based on the fact that these shifts excellently correlate with the hyperfine coupling constants obtained from the graphical analysis of 13C shifts induced by other Ln(fod)3, where Ln is La, Pr, Nd, Sm, Eu, Dy, Ho, Er, or Yb. It was found from the INDO MO calculations of the spin densities of ligand moieties that these Gd-induced shifts parallel the spin-density distribution of the naphthylmethyl radical better than that of the naphthylamine cation radical and that these shifts are best interpreted in terms of the superposition of the β-spin of the naphthylmethyl radical and the α-spin of the naphthyl radical. This may suggest that a direct spin transfer occurs through space from Gd3+ to the amine molecule, in addition to the normal through-bond delocalization via the N-lone pair.
Pattern Formation by Rhythmic Crystallization of Methyl Mesitylcarbamate
Authors: Iwamoto Kazutoshi , Mitomo Shun-ichi , Fukide Jun-ichi , Shigemoto Tadashi , Sen\={o} Manabu
Published: July 2006

Rhythmic crystallization behavior of methyl mesitylcarbamate from chloroform solutions under appropriate conditions was found. Effects of temperature, evaporation rate of solvent, and sample weight per area on this behavior are studied in detail, and the qualitative explanation based on the autocatalytic branching process is proposed.
Kinetics of Racemization and Dissociation of Tris(1,10-phenanthroline)iron(II). Hydrophobic Interaction between the Complex Cation and Alkylammonium Cations
Authors: Tachiyashiki Satoshi , Yamatera Hideo
Published: July 2006

The rates of racemization and dissociation of [Fe(phen)3]2+ were determined in the presence of series of alkali-metal bromides, symmetrical tetraalkylammonium bromides, and alkyltrimethylammonium bromides. The alkali-metal bromides did not affect the racemization rate, but they decreased the dissociation rate. The retarding effect increased with increasing bromide concentrations and decreased in the order of Li+>Na+>K+> Rb+>Cs+. The alkylammonium bromides increased the racemization rate up to three fold and decreased the dissociation rate down to half the rate in pure water; alkylammonium ions with longer alkylchains induced greater changes of the rates. The effect of alkylammonium ions on the reaction rates was analyzed in terms of the formation of 1:1 aggregates of the complex cation with the alkylammonium cation caused by hydrophobic interactions. The equilibrium constant for the aggregate formation was greater for the alkylammonium ions with longer alkyl chains. The reaction rate constants of the hydrophobic aggregates remain almost constant with the increase in the alkyl chain length. The rate behaviors of the hydrophobic aggregates are discussed in terms of the reaction mechanisms of racemization and dissociation of [Fe(phen)3]2+.
Formation of Mixed-ligand Complexes of Cobalt(II) with Bromide and Substituted Pyridines in 1,2-Dibromoethane
Authors: Sawada Kiyoshi , Miura Kazue , Suzuki Toshio
Published: July 2006

The equilibria of a series of complexes of the CoBr2(R-py)2 type (where R-py=2-methyl-(2Me-py), 3-methyl-(3Me-py), 4-methyl-(4Me-py), 4-acetyl-(4Ac-py), and 4-cyanopyridine (4CN-py), and pyridine(py)) with TBA·Br (tetrabutylammonium bromide) in 1,2-dibromoethane have been investigated spectrophotometrically. In the presence of an excess of R-py, the dibromocomplex gives rise to the following configurational equilibrium:

CoBr2(R-py)2+2R-py\oversetkc\ightleftharpoonsCoBr2(R-py)4

(tetrahedral)&(octahedral)

with logKc=0.67, 0.11, and 0.53±0.03 for the 4Me-py, 3Me-py, and py complexes respectively. The substitution equilibria of the tetrahedral complexes are written as:

CoBr2(R-py)2+TBA·Br\oversetk3\ightleftharpoons(TBA)CoBr3(R-py)+R-py,

(TBA)CoBr3(R-py)+TBA·Br\oversetk4\ightleftharpoons(TBA)2CoBr4+R-py.

The successive formation constants, logK3, were determined as 2.23, 2.44, and 2.89±0.03 for the 4Me-py, 3Me-py, and py complexes respectively. The constants logK4 for the 4Me-py, 3Me-py, 2Me-py, py, 4Ac-py and 4CN-py complexes are −1.07, −0.94, 0.09, −0.74, −0.09, and 0.47±0.01 respectively. The values of logK3 and logK4 show a linear correlation with the basicity of R-py, pKb, except for the 2Me-py complex.
Temperature-jump Studies of the Complex Formation of Nickel(II) l-Glutamate in Aqueous Solutions
Authors: Tamura Kiyoshi , Harada Shoji , Funaki Yoshinori , Yasunaga Tatsuya
Published: July 2006

Temperature-jump relaxation studies have been carried out on aqueous nickel(II)–l-glutamic acid solutions. The observed relaxation phenomenon is ascribed to the successive complex formation reactions:

Ni2++L2− \oversetk1\undersetk-1\ightleftharpoons NiL,

NiL+L2− \oversetk2\undersetk-2\ightleftharpoons NiL22−,

NiL22−+L2− \oversetk3\undersetk-3\ightleftharpoons NiL34−,

where L2− denotes a glutamate ion. The rate constants are: 2.0×104, 1.1×104, and 9.2×103 M−1 s−1 (1 M=1 mol dm−3) for k1, k2, and k3, and 0.048, 0.69, and 27 s−1 for k−1, k−2, and k−3, respectively, at 25 °C and I=0.1. The rate-determining step of the complex formation reactions, which follows the initial formation of ion-pairs, is the dissociation of a water molecule from the inner hydration sphere of the nickel; the glutamate ion acts as a bidentate ligand forming a five-membered chelate ring in the complexes.
Chemistry of Chiral Vitamin B6 Analogs. IV. Syntheses of Chiral Pyridoxal and Pyridoxamine Analogs Having a Branched “Ansa Chain” between 2′- and 5′-Positions
Authors: Ando Makoto , Tachibana Yoji , Kuzuhara Hiroyoshi
Published: July 2006

Racemic 15-formyl-14-hydroxy-5,5-dimethyl-2,8-dithia[9](2,5)pyridinophane (4), an analog of pyridoxal having a branched “ansa chain” between 2′- and 5′-positions, was synthesized from 2,5-bis(chloromethyl)-3-hydroxy-O,O′-isopropylidene-4-pyridinemethanol. Optical resolution of 4 was achieved via the formation of Schiff base with 3-amino-3-deoxy-1,2:5,6-di-O-isopropylidene-d-glucofranose, giving the levorotary enantiomer of 4 (4a). Racemic 15-aminomethyl-14-hydroxy-5,5-dimethyl-2,8-dithia[9](2,5)pyridinophane (5), the same type of pyridoxamine analog as 4, and its levorotary enantiomer were synthesized from the corresponding 4 and 4a. Both levorotary and dextrorotary enantiomers of 5 were also obtained by the optical resolution of the racemate via the formation of chiral dibenzoyltartaric acid salts of 5.
The C(1)–C(10) Bond Cleavage and B Ring Aromatization of Some 6-Hydroxy-5βH-abieta-6,8,11,13-tetraen-18-oic Acid 18,6-Lactones
Authors: Matsumoto Takashi , Imai Sachihiko , Ondo Kenji , Takeyama Nobuaki , Kataoka Hideo , Yamamoto Yasuhiro , Fukui Kenji
Published: July 2006

Fusion of 6-hydroxy-5βH-abieta-6,8,11,13-tetraen-18-oic acid 18,6-lactone (2) with potassium hydrogensulfate at 220 °C afforded bis[3-(2,3-dihydro-7-isopropyl-3,4-dimethyl-2-oxonaphtho[2,3-b]furan-3-yl)propyl] ether (12) in 37% yield, together with two minor products in 12% yield: 2,3-dihydro-7-isopropyl-3,4-dimethyl-3-propylnaphtho[2,3-b]furan-2-one and 3-allyl-2,3-dihydro-7-isopropyl-3,4-dimethylnaphtho[2,3-b]furan-2-one. Treatment of 12 with p-toluenesulfonic acid at 160 °C gave 2,3-dihydro-7-isopropyl-3,4-dimethyl-3-(3-tosyloxypropyl)naphtho[2,3-b]furan-2-one, which was converted into 2,3-dihydro-3-(3-hydroxypropyl)-7-isopropyl-3,4-dimethylnaphtho[2,3-b]furan-2-one (16). The alcohol 16 was further characterized as its acetate (17). After several attempts, the above C(1)–C(10) bond cleavage and B ring aromatization reaction were improved by use of concentrated sulfuric acid in refluxing acetic acid. Under these conditions, 2 gave 17 in 47% yield. Hydrolysis of 17 with hydrochloric acid afforded 16. Subsequently, 12-hydroxy-, 12-methoxy-, 12-acetoxy-, and 12-nitro-6-hydroxy-5βH-abieta-6,8,11,13-tetraen-18-oic acid 18,6-lactones were each refluxed with concentrated sulfuric acid in acetic acid to give 6-hydroxy-, 6-methoxy-, 6-acetoxy-, and 6-nitro-3-(3-acetoxypropyl)-2,3-dihydro-7-isopropyl-3,4-dimethylnaphtho[2,3-b]furan-2-ones, respectively. From the present study, the 12-acetoxy derivative seems to be a suitable intermediate for the synthesis of coleon A.
Microwave Spectra of cis- and trans-1-Chloro-1,2-difluoroethylene
Authors: Ogata Teruhiko
Published: July 2006

The microwave spectra of the 35Cl and 37Cl isotope species of cis- and trans-HFC=CFCl have been studied in the 8–50 GHz region. The rotational constants and the Cl quadrupole coupling constants in MHz are obtained and listed. The quadrupole coupling constants and the structures obtained for cis- and trans-HFC=CFCl are consistent with the results of other haloethylenes.

(Remark: Graphics omitted.)
Solvent Effects in the Conversion of Phenyldiazomethane into Stilbene and Spirooxetane in the Reaction with Chloranil
Authors: Oshima Takumi , Nishioka Ryoji , Nagai Toshikazu
Published: July 2006

A stereochemical study was made of the reaction of phenyldiazomethane(1) with chloranil(2) at 20 °C in 28 aprotic solvents. The products were trans-spirooxetane(4) and cis-trans mixtures of stilbene(3) (ca. 2–5 times cis-rich). The molar ratios of cis-3 to the sum of the trans-3 and 4 tended to increase, whereas the 4 to trans-3 ratios decrease with the increase in the solvent basicity and polarity. These effects of solvents on the product distributions were interpreted in terms of the effects of the solvent basicity and polarity on the stereoselective formation of the diazonium betaine intermediate and on the conformational isomerism. Moderately successful linear-free-energy(LFE) relationships were established for these product ratios with the aid of the combination of the empirical solvent basicity parameter, Dπ, and the Kirkwood function, f(ε), or ET values as the solvent polarity parameters.
Liquid Crystals as Reaction Media. I. Photochemical Dimerization of Acenaphthylene in Cholesteric Liquid Crystal
Authors: Nakano Tomoko , Hirata Hirotaka
Published: July 2006

The photodimerization of acenaphthylene in liquid crystalline media exhibiting cholesteric or nematic phase was studied from the view point of the stereoselectivity of the products. In the cholesteric phase trans-isomer formation increased remarkably and the ratio of the trans-isomer to cis-isomer depended significantly upon the acenaphthylene concentration. These results suggest a steric effect of the cholesteric phase structure on stereoselectivity on photodimerization compared with the predominant cis-isomer formation in the nematic phase.
Syntheses of Six-membered Cyclopalladated Complexes of 2-Benzoylpyridine
Authors: Fuchita Yoshio , Hiraki Katsuma , Kage Yasunori
Published: July 2006

2-Benzoylpyridine reacts with Pd(OAc)2 to give a new six-membered cyclopalladated complex, [{Pd(pcph)(OAc)}2]·0.25CH2Cl2 [pcph=2-(2-pyridylcarbonyl)phenyl-C1,N] (1). A chloro-bridged analogue, [{Pd(pcph)Cl}2], prepared by the metathetical reaction of 1 with LiCl, undergoes bridge-splitting reactions with 3,5-lutidine and Tl(acac) to yield the corresponding mononuclear cyclopalladated complexes.
On the Effect of the Finite Size of the Solvent Molecule in Dielectric Friction Theory
Authors: Hyodo Shi-aki , Nagashima Unpei , Fujiyama Tsunetake
Published: July 2006

By considering the charge distribution function around the ion, the effect of the finite size of the solvent molecule can be introduced in the homogeneous dielectric continuum model. A very simple and useful model is presented. The results of this model are compared quantitatively with the experimental Walden products of some simple cations in water, methanol, ethanol, acetone, and acetonitrile solutions, and found to be satisfactory.
A Nuclear Magnetic Resonance Study of the Kinetics of Ligand Exchange Reactions in Uranyl Complexes. III. Dimethyl Sulfoxide Exchange in Bis(β-diketonato)(dimethyl sulfoxide)dioxouranium(VI)
Authors: Ikeda Yasuhisa , Tomiyasu Hiroshi , Fukutomi Hiroshi
Published: July 2006

The exchange reactions of dimethyl sulfoxide (DMSO) with UO2(acac)2dmso and UO2(dbm)2dmso (acac=acetylacetonate, dbm=dibenzoylmethanate) have been studied by the NMR method in CD3COCD3 and CD2Cl2. In CD3COCD3, rates of DMSO exchange for these complexes are independent of the free DMSO concentrations. Rate constants (s−1) at 25 °C and activation parameters ΔH\eweq (kJ mol−1) and ΔS\eweq (J K−1 mol−1) are 2.36×102, 45.8±0.8, −46.6±2.9 for UO2(acac)2dmso, and 3.92×102, 44.5±0.4, −46.2±2.1 for UO2(dbm)2dmso, respectively. In CD2Cl2, the exchange rates are dependent on the free DMSO concentration. For UO2(acac)2dmso, rate=(kd+kIKOS[DMSO])[UO2(acac)2dmso]/(1+KOS[DMSO]), where kd(25 °C=1.02×102 s−1, ΔH\eweq=47.9±5.2 kJ mol−1, and ΔS\eweq=−46.6±11.2 J K−1 mol−1, and kI(25 °C)=1.01×103 s−1, ΔH\eweq=35.4±12.4 kJ mol−1, and ΔS\eweq=−69.7±20.5 J K−1 mol−1, and KOS(10 °C)=4.6±2.1 M−1 (M=mol dm−3). For UO2(dbm)2dmso, rate=(k1+k2[DMSO]) [UO2(dbm)2dmso], where k1(25 °C)=1.74×102 s−1, ΔH\eweq=29.6±2.2 kJ mol−1, ΔS\eweq=−104±9 J K−1 mol−1, and k2(25 °C)=1.62×103 M−1 s−1, ΔH\eweq=34.9±0.6 kJ mol−1, and ΔS\eweq=−67.2±2.4 J K−1. The D and I mechanisms are proposed for the DMSO exchange in these complexes.
Phase Equilibria in the Tm2O3–V2O3–V2O5 System at 1200 °C
Authors: Kitayama Kenzo , Katsura Takashi
Published: July 2006

Phase equilibria in the Tm2O3–V2O3–V2O5 system were established at 1200 °C; the oxygen partial pressure was varied −0.68 (air) to −12.50 atm in terms of log Po2. In this system, VnO2n−1 (n=2–7), VO2, Tm2O3, TmVO3, TmVO4, Tm8V2O17 (4Tm2O3·V2O5), Tm7V3O16 were stable under the present experimental conditions. The pattern of the phase diagram is different from those of other Ln2O3–V2O3–V2O5 systems (Ln=Sm, Lu, Er, Gd, La, and Nd) that were already established. Compounds TmVO3, TmVO4, Tm8V2O17, Tm7V3O16, V2O3, and VO2 have nonstoichiometric compositions. On the basis of the established phase diagram, the Gibbs energies of the reactions,

(1) 2Tm2O3+3TmVO3+1⁄2O2=Tm7V3O16

(2) TmVO3+1⁄2O2=TmVO4

(3) 5⁄3Tm2O3+2⁄3Tm7V3O16+2⁄3O2=Tm8V2O17

(4) Tm7V3O16+O2=5⁄3TmVO4+2⁄3Tm8V2O17

were determined to be −132, −119, −157, and −228 kJ, respectively. The relationship between the ionic radius and ΔG° of the reactions, LnVO3+1/2 O2=LnVO4, is linear, provided that lanthanum and the lanthanoid can be divided into two groups.
Retentive Friedel-Crafts Alkylation of Benzene with Optically Active 2-Chloro-1-phenylpropane and 1-Chloro-2-phenylpropane
Authors: Masuda Shinji , Nakajima Tadashi , Suga Sohei
Published: July 2006

Alkylations of benzene with both (−)-2-chloro-1-phenylpropane (1) and (+)-1-chloro-2-phenylpropane (2) in the presence of Lewis acid gave the same products: (−)-1,2-diphenylpropane (3), 1,1-diphenylpropane, and polymeric materials. In these reactions, (−)-3 was obtained in 45–100% optical yield and was not racemized under the conditions used. These results reveal that the reaction from 1 to 3 proceeds with retention of configuration and that from 2 to 3 with inversion. The stereochemistry of the alkylation with 1 is elucidated by the mechanism involving a neighboring phenyl π-assisted cation; benzene attacks only the β-carbon of 1 from the side on which the previously attached chloride anion is located. The result of the reaction with 2 can be explained by a process involving the 1,2-shift of phenyl group in the ionization step of 2, followed by the formation of the same intermediate as in the reaction with 1. The mechanism of the overall reaction is discussed.
Bitter Limonoids from the Fruit of Melia azedarach L. var. japonica Makino
Authors: Fukuyama Yoshiyasu , Miura Iwao , Ochi Masamitsu
Published: July 2006

Two new bitter limonoids, ohchinolal (1) and ohchinin (2), have been isolated from the fruit of Melia azedarach L. var. japonica Makino, and their structures have been established as 1 and 2 by spectroscopic and chemical methods. The complete assignments of the 1H and 13C NMR data are described.
Ditritylation of Methyl and Benzyl α-d-Gluco-, -Manno-, and -Galactopyranosides and Preparation of Their Partially Benzylated Derivatives
Authors: Koto Shinkiti , Morishima Naohiko , Yoshida Toyosaku , Uchino Masaharu , Zen Shonosuke
Published: July 2006

The ditritylation of methyl and benzyl α-d-gluco-, -manno-, and -galactopyranosides with trityl chloride in pyridine at 70 °C proceeds in a regioselective manner to give the 2,6-ditrityl ethers of the glucosides, the 3,6-ones of the mannosides, and both 2,6- and 3,6-ones of the galactosides. The rearrangement of the trityl group from O-3 to O-2 of the mannosides at 100 °C causes the selective formation of the 2,6-ditrityl ethers. From the 2,6- and the 3,6-ditrityl ethers, the 3,4- and 2,4-dibenzyl ethers of the hexopyranosides are prepared.
3-Chloro-2-chloromethyl-4-(4-chlorophenoxy)-1-butene as a Functionalized Isoprene Unit. An Electrochemical Preparation and Some Reactions
Authors: Uneyama Kenji , Hasegawa Nobu , Kawafuchi Hiroyuki , Torii Sigeru
Published: July 2006

3-Chloro-2-chloromethyl-4-(4-chlorophenoxy)-1-butene (1) was prepared in 72% yield by electrooxidative double ene-type chlorination of 1-(4-chlorophenoxy)-3-methyl-2-butene. The electrolysis was conducted at room temperature in a two layer solvent system of dichloromethane and water in the presence of acids (HCl, H2SO4, H3PO4, etc). Either 3-chloro-2-methyl-4-(4-chlorophenoxy)-1-butene or 1 was selectively prepared, respectively after 4 or 10 F/mol of electricity were passed using platinum foils as electrodes in an undivided cell. The similar electrolysis of the related 3-methyl-2-butenyl derivatives 2b and 2c provided the ene-type products, 3-chloro-2-methyl-4-benzyloxy-1-butene and 4-chloro-1-ethynyl-1,5-dimethyl-5-hexenyl acetate, respectively. In contrast, 3-methyl-2-butenyl derivatives 2d–f and 3-methyl-2-butenoic acid afforded a variety of products such as chlorohydrin, vinyl chloride, and sulfoxide other than ene-type products, suggesting that the functional group of R in 2 affects the reaction course. The elongation at 2-chloromethyl group and the subsequent dechlorophenoxylation convert 1 into 2-(phenylsulfonylmethyl)-1,3-butadiene and 2-(phenylthiomethyl)-1,3-butadiene.
Preparation of New Nitrogen-bridged Heterocycles. 6. First Synthesis of 2-Aroylfuro[2,3-b]indolizine Derivatives
Authors: Kakehi Akikazu , Ito Suketaka , Ohizumi Tsuyoshi , Ito Masayoshi
Published: July 2006

Alkaline treatment of 2-(aroylmethoxy)-3-(2,2-dicyanovinyl)indolizine derivatives, readily available from the step-by-step reactions of 1-(ethoxycarbonylmethyl)-2-picolinium salts with a base, (ethoxymethylene)malononitrile followed by some phenacyl bromides in ethanol, afforded smoothly the title compounds, 2-aroylfuro[2,3-b]indolizine derivatives, in good yields. These furoindolizines could be also obtained directly from the pyridinium salts without the isolation of intermediate 3-vinylindolizines. Formation mechanisms and some physical properties of these furoindolizines are also discussed.
Selective Oxidation of Sulfides to Sulfoxides by a Polymeric Reagent Electrochemically Generated and Recycled in Situ
Authors: Yoshida Jun-ichi , Sofuku Hiroshi , Kawabata Nariyoshi
Published: July 2006

A polymeric reagent electrochemically generated from crosslinked poly(4-vinylpyridine) hydrobromide was found to oxidize sulfides to give sulfoxides in high yields. The exhausted polymeric reagent was regenerated by continuous electrochemical oxidation in situ.
The Synthesis of Cyclohepta[4,5]pyrrolo[2,3-d]thiazoles
Authors: Fujimori Kunihide , Hirako Nobuhiro , Yamane Kameji
Published: July 2006

Cyclohepta[4,5]pyrrolo[2,3-d]thiazole and its amino derivatives were obtained in a few steps by starting with 2-amino-1-azaazulene.
Dimethyl and Diethyl 2-Oxo-1,3-propanedisulfonates as Practical Alkylating Reagents
Authors: Ogura Fumio , Yamaguchi Hachiro , Otsubo Tetsuo , Nakano Takao , Saito Takahiro
Published: July 2006

The title sulfonates, easily accessible from acetone, were found to be effective and practical alkylating agents.
Stereochemistry and Properties of unsym-fac-, sym-fac- and mer- (Iminodiacetato)n(N-alkyliminodiacetato)2−nCobaltate(III)(n=0, 1, or 2) Complexes
Authors: Yasui Takaji , Kawaguchi Hiroshi , Koine Norio , Ama Tomoharu
Published: July 2006

Unsymmetrical-facial (u-fac) and symmetrical-facial (s-fac) isomers of a mixed-ligand type complex, [Co(ida)(Rida)]− (Rida denotes N-methyl- or N-ethyliminodiacetate dianion), were prepared and characterized on the basis of their absorption, circular dichroism, 1H NMR, and 13C NMR spectral data. The isomerization and racemization reactions of these isomers were investigated in basic aqueous solution and compared with those of the bis type complexes, [Co(ida)2]− and [Co(Rida)2]−. The time-course changes in the absorption spectra of [Co(ida)(Rida)]− and [Co(ida)2]− indicated that the mer isomer exists as a transient labile intermediate in the isomerization reaction of u-fac to s-fac.
Crystal and Molecular Structure of [11,13-Dimethyl-12-(p-methylbenzoyl)-1,4,7,10-tetraaza-10,12-cyclotridecadienato]nickel(II) Hexafluorophosphate
Authors: Matsumoto Naohide , Ohyoshi Akira
Published: July 2006

The title complex prepared through an electrophilic substitution of (11,13-diemthyl-1,4,7,10-tetraaza-10,12-cyclotridecadienato)nickel(II) bromide with p-methylbenzoyl chloride was subjected to single-crystal X-ray diffraction analysis. The analysis has revealed completion of the substitution reaction, pseudo C2 symmetry of the macrocyclic complex minus the substituent, and an essentially square planar coordination environment with slight tetrahedral distortion. The substituted p-methylbenzoyl group is tilted with respect to the least-squares plane of the conjugated six-membered chelate ring, where the dihedral angle between them is 69.2°.
The Reaction of cyclo-Triphosphate with Ethylenediamine
Authors: Tsuhako Mitsutomo , Nakahama Akiko , Ohashi Shigeru , Nariai Hiroyuki , Motooka Itaru
Published: July 2006

The reaction of sodium cyclo-triphosphate (P3m) with ethylenediamine (en) was studied with special attention paid to the kinds and amounts of products under various conditions and to its reaction mechanism. 1) The reaction of P3m with ethylenediamine in the pH range of 8–12 gave six new compounds; three of them were identified as N,N-bis(2-aminoethyl)phosphorodiamidate (P1-en2), N-(2-aminoethyl)amidodiphosphate (P2-en), and N-(2-aminoethyl)-P-amidotriphosphate (P3-en). 2) The formation of P3-en and P2-en was most favored at a pH near 10(about 32 and 9% respectively), while that of P1-en2 proceeded extensively at pH 10–12(about 12%). 3) The amounts of products varied greatly depending on the mixing ratio of P3m and ethylenediamine. P1-en2 was the predominant product at en/P3m>1, while P3-en was at en/P3m≤1. 4) At a pH value below 10, tetra(P4) and pentaphosphate (P5) were formed in addition to the above products. The reaction between P3m and ethylenediamine scarcely proceeded under acidic conditions. 5) Ortho-(P1), pyro-(P2), and triphosphate (P3) did not react with ethylenediamine at all. 6) The reaction mechanism between P3m and ethylenediamine was discussed.
Pyrolytic Sulfurization Gas Chromatography. XIV. Simultaneous Determination of the Absolute Contents of C, H, O, and N in an Organic Compound by Means of a Calibration Method
Authors: Hara Tadashi , Okui Fujio
Published: July 2006

The absolute content of C, H, O, and N in an organic compund including a metal organic chelate was satisfactorily determined on the basis of pyrolytic sulfurization gas chromatography. A 1.0–1.3 mg sample was weighed on a microbalance, and was subjected to pyrolytic sulfurization. The gases evolved by the reaction were estimated by gas-chromatography. By using both the analytical result of each product and its calibration factor previously obtained by analyzing cyanoguanidine, 8-quinolinol, and sucrose as standard samples, the absolute content of C, H, O, and N was calculated satisfactorily for each substance.
Determination of a Small Amount of Biological Constituent by Use of Chemiluminescence. I. The Flow-injection Analysis of Protein
Authors: Hara Tadashi , Toriyama Motohiro , Tsukagoshi Kazuhiko
Published: July 2006

A new method in which luminol-hydrogen peroxide luminescent system is used has been proposed for the determination of the presence of protein. Since the catalytic activity of copper(II) for the chemiluminescent reaction between luminol and hydrogen peroxide decreased when copper(II) interacted with polypeptide linkage, this phenomenon was applied to the determination of protein. Determination of protein was carried out by a flow-injection method. The effects of reagent concentration, flow-rate, and reaction time on the analytical value were examined and the conditions for the determination of protein were established. Similar calibration curves were obtained for human serum albumin, bovine serum albumin, bovine serum α-globulin, and bovine serum γ-globulin. According to the present flow-injection method using chemiluminescent reaction, a small amount of protein could be conveniently and economically determined over a wide range of concentration, 7×10−4–7×10−2 g dm−3, with the detection limit of 0.2 μg and at the rate of about 30 samples per hour. The present method was applicable to the determination of protein in serum.
Magnetic Property and Crystal Structure of Alkoxo-bridged Bi- and Tetranuclear Copper(II) Complexes with Condensation Products of 3-Ethoxymethylene-2,4-pentanedione and Amino Alcohols
Authors: Matsumoto Naohide , Tsutsumi Toshihiro , Ohyoshi Akira , Okawa Hisashi
Published: July 2006

Alkoxo-bridged polynuclear copper(II) complexes with condensation products of 3-ethoxymethylene-2,4-pentanedione and each of three amino alcohols, 2-aminoethanol, 3-amino-1-propanol, and 1-amino-2-propanol, were prepared and characterized by elemental analyses, infrared spectra, electronic spectra, molecular weight measurements, magnetic susceptibility measurements, and crystal structure analysis, the complexes being abbreviated as Cu(L-2), Cu(L-3), and Cu(L-2m), respectively. Cu(L-3) is a dimer, but Cu(L-2m) and Cu(L-2) are tetramers. The magnetic susceptibility of violet Cu(L-3), whose electronic spectrum exhibits a d-d band maximum at 17.7×103 cm−1, is in conformity to the Bleaney-Bowers equation with exchange integral −2J=920 cm−1. Cu(L-3) consists of alkoxo-bridged centrosymmetric binuclear units, where the geometries around the copper ion and bridged oxygen atom are planar and the angle of Cu–O–Cu is 103.6(1)°. The magnetisms of blue complexes Cu(L-2) and Cu(L-2m) exhibiting a d-d band maximum at 15.7×103 cm−1 obey the Curie Weiss law with positive Weiss constants 17 and 20 K, respectively, and are in accord with the Heisenberg model based on a tetranuclear cubane-like structure.
Photoinduced Alcoholysis of α,α,α-Tribromoacetophenone to Benzoylformate
Authors: Izawa Yasuji , Ishiguro Katsuhiro , Tomioka Hideo
Published: July 2006

Irradiation of p-substituted α,α,α-tribromoacetophenones (1) in O2-saturated alcohols (MeOH, prim. and sec. alcohols) afforded a new alcoholysis product, benzoylformate (2), in good yield (75–85%) along with benzoate and radical (reduction) products. Sensitization experiments showed that 2 was derived from the triplet excited 1. Formation of 2 as well as the decomposition rate of 1 were greatly accelerated by oxygen, presumably as a result of the involvement of the normally forbidden S0→T1 transition of 1 due to the oxygen-1 charge transfer complex. Independent synthesis and reaction of possible intermediates in the photoalcoholysis of 1 leading to 2 suggested that 2 was formed from spontaneous (dark) reactions of initial photoalcoholysis product, α,α-dibromo-α-alkoxyacetophenone.
Preparation and Characterization of Poly(thienylene)s
Authors: Yamamoto Takakazu , Sanechika Ken-ichi , Yamamoto Akio
Published: July 2006

Nickel compounds (NiCl2 and NiCl2(2,2′-bipyridine)) catalyze polycondensation of dihalothiophenes (2,5-dihalothiophenes, 2,4-dibromothiophene, and 3-methyl-2,5-dibromothiophene) by dehalogenation with magnesium to give the corresponding poly(thienylene) type polymers (poly(2,5-thienylene), poly(2,4-thienylene), and poly(3-methyl-2,5-thienylene)). Copolymerization of 2,5-dibromothiophene and 2,4-dibromothiophene affords copolymers formulated as (\llap–2,5-C4H2S) \llap–m(\llap–2,4-C4H2S) \llap–n. About 15 wt% of poly(2,5-thienylene) prepared in THF at 66 °C is soluble in CHCl3 at room temperature and the CHCl3-soluble fraction has a molecular weight of 1370. The remaining fraction is considered to have a higher molecular weight as judged from its physical properties. IR and 1H-NMR spectra of the polymers are consistent with the structures described above. The electronic spectra of poly(2,5-thienylene) and poly(3-methyl-2,5-thienylene) show large bathochromic shifts of the π-π* absorption bands from those of thiophene and 3-methylthiophene, respectively, indicating that π-electrons in these polymers are extensively delocalized along the polymer chains. In contrast to the electronic spectra of these polymers, that of poly(2,4-thienylene) shows only a minor shift of the π-π* absorption band from that of thiophene reflecting the less extensive π-electron delocalization along the polymer chain in the poly(2,4-thienylene). All the polymers are nonsensitive to air and have high thermal stabilities.