bluuebunny/crossref_metadata_2025_split huggingface dataset:
Direct Synthesis of Ethylene Glycol from Carbon Monoxide and Hydrogen by Use of Rhodium Catalyst. The Effect of Amine Promoters and Their Roles
Authors: Masuda Takashi , Murata Kazuhisa , Matsuda Akio 
Published: July 2006

Abstract
The influence of addition of amines on the direct synthesis of ethylene glycol (EG) has been investigated using a rhodium catalyst under a high pressure (1800 kg cm−2). The addition of amines improved the catalyst activity and selectivity for the EG formation and the stability of the catalyst. The addition of amines further resulted in glycerol (GL) formation. Optimum amine/rhodium ratios for the EG formation were 50–100 in tetrahydrofuran solvent with a low polarity and 1–3 in γ-butyrolactone solvent with a high polarity. Optimum N/Rh ratios and IR spectra of reaction solutions suggested that amine promoters serve to accelerate the formation of mononuclear Rh species from the catalyst precursor. It was also suggested that amines promote formation of a Rh–CH2OH complex and insertion of CO. Bulky amines such as triisobutylamine, N-ethylcarbazole, triisopropanolamine, and tribenzylamine were especially effective promoters for the formation of EG and GL. The effectiveness of bulky amines as the promoter is discussed.
NMR Spectra of Organogermanium Compounds. VI. NMR Spectra and Molecular Mechanics Calculations of 3-Methyl- and 3,3-Dimethylgermacyclohexanes
Authors: Takeuchi Yoshito , Ichikawa Yasuko , Tanaka Katsumi , Kakimoto Norihiro 
Published: July 2006

Abstract
Several 3-methyl- or 3,3-dimethylgermacyclohexanes were prepared and their 13C and 73Ge NMR spectra were determined. Steric energies for all of stereoisomers of some of these germacyclohexanes were calculated by MM2 program. The effect of axial 3-methyl group of germacyclohexanes upon its C-5 is much the same with the corresponding effect in cyclohexanes, and is much smaller than the effect caused by axial methyl on germanium upon C-3,5. A large upfield shift is recorded for germanium nuclei when there is an axial methyl on C-3 of germacyclohexanes.
Formation of 4-Benzamidoisoxazole Derivatives
Authors: Zen Shonosuke , Harada Kazuho , Nakamura Hikaru , Iitaka Yoichi 
Published: July 2006

Abstract
The titled compounds (3) were synthesized by the reaction of nitrile oxides with 1-azirines and also the reaction of aliphatic nitro compounds with dibenzoylmethane derivatives in the presence of acetyl chloride and sodium methoxide. The structure of 3 was established by single crystal X-ray analysis. A mechanism of the formation for 3 is proposed.
The Reaction of 1-Amino-2,3-diphenylcyclopropenium Ions with 1,3-Diketones to Afford 2,4-Cyclopentadien-1-ols: The Regioselective Ring-Opening of 1-Aminocyclopropene Intermediates
Authors: Yoshida Hiroshi , Tamai Tomoji , Ogata Tsuyoshi , Matsumoto Kiyoshi 
Published: July 2006

Abstract
1-Amino-2,3-diphenylcyclopropenium tetrafluoroborates (4) reacted with cyclic or acyclic 1,3-dicarbonyl derivatives (5) such as 1,3-diketones, β-keto esters, or gem-diesters in the presence of triethylamine to give 2,4-cyclopentadien-1-ols in moderate to good yields. Some isolated cyclopropene intermediates were, upon heating, converted to the corresponding cyclopentadienols. The factors that influence on the reactivities of 4 and 5 (basicities of the amino groups of 4 and bulkiness of the substituents of 4 and 5) are discussed qualitatively.
Radical Transport Reaction. Concurrent Transfer of Electron and Proton
Authors: Ichikawa Junji , Sonoda Takaaki , Kobayashi Hiroshi 
Published: July 2006

Abstract
Concurrent transport of electron and proton on the same molecule; formal hydrogen-transfer reaction, is successfully realized in aprotic media by using 1-butyl-4,4′-bipyridinium cation radical (BuPPH\underset.+), which is prepared from 1-butyl-4-(4-pyridyl)pyridinium ion. Hydrogen reduction with BuPPH\underset.+ was discriminated from electron reduction with octylviologen cation radical by the chemoselective reduction preferring enedione to vic-dibromide in aprotic media.
Effects of Crown-Type Host–Guest Complexation on Electrochemical Profiles of Pb2+ Ion
Authors: Tsukube Hiroshi , Takagi Kentaro , Higashiyama Tatsuo , Iwachido Tadashi , Hayama Naomi 
Published: July 2006

Abstract
Crown ethers, cryptands, and related synthetic host molecules modified electrochemical profiles of Pb2+ ion by host–guest complexations. The reduction potentials of the Pb2+ complexes were significantly correlated with their complex stabilities.
Electron Spin Resonance Studies of Anion Radicals of Benzoylsilanes
Authors: Mochida Kunio , Yamamoto Keiji 
Published: July 2006

Abstract
ESR studies of anion radicals of seven substituted benzoylsilanes were investigated. ESR data of these anion radicals are discussed in comparison with those of aryl alkyl ketones. ESR spectra of secondary product derived from the anion radical of benzoylsilanes were also examined.
Partial Oxidation of Isobutene to Methacrylic Acid on V2O5–P2O5 Catalysts
Authors: Ai Mamoru 
Published: July 2006

Abstract
The vapor-phase air oxidation of isobutene was studied with V2O5, V2O5–TiO2, V2O5–MoO3, V2O5–P2O5, V2O5–P2O5–TeO2, and heteropoly compound catalysts, such as H3PMo12O40, Cs2HPMo12O40, H5PMo10V2O40, and Cs2.5H2.5PMo10V2O40, in the presence of water vapor. On pure V2O5, the oxidation products were acetic acid and carbon oxides, plus small amounts of acetone and methacrylaldehyde. With the addition of TiO2 to V2O5, the selectivity to acetic acid increased a little, but the formation of methacrylaldehyde disappeared. The addition of MoO3 to V2O5 enhanced the formations of acetone and methacrylaldehyde, to a certain extent, but methacrylic acid was not obtained. With the V2O5–P2O5 catalysts, the yield of methacrylic acid attained 21 mol%, the sum of the yields of methacrylaldehyde and methacrylic acid attained 30 mol%, and the yield of acetic acid attained also 30 mol%. The P/V atomic ratio=1.6 catalyst was better than the P/V=1.06 catalyst in the formation of methacrylic acid. Further, the performance of the P/V=1.6 catalyst was better than that of the heteropoly compound catalysts. The results were discussed in the light of the acid–base properties of the catalysts.
The CH-Surface Area of Sugar Molecules as a Measure of Their Potential Hydrophobicity
Authors: Yano Yuki , Tanaka Keiko , Doi Yukio , Janado Masanobu 
Published: July 2006

Abstract
Differential affinity of three groups of sugars (monosaccharides, glucodisaccharides and methyl glycosides) can reasonably be interpreted in terms of a molecular surface parameter, the ratio of the surface area of hydrophobic groups (CH, CH2, and CH3) to that of hydrophilic groups (OH and –O–) computed from the crystallographic data.
Solvatochromism of the Co(III) Complexes with Macrocyclic N3O3-Type Ligands
Authors: Fujiwara Mika , Yoshitake Michiko , Fukuda Yutaka , Sone Kozo 
Published: July 2006

Abstract
The color and visible spectrum of [Co(tacnta)] and [Co(tacntp)]·3H2O depend remarkably on the acceptor number of the solvent, as also do those of K[Co(edta)]·2H2O and related chelates. The changes are especially large in the case of [Co(tacntp)]·3H2O, extending to solvents of high acidity. A plausible explanation is given for this solvatochromism.
Pheophytinization of Chlorophyll a and Chlorophyll a′ in Aqueous Acetone
Authors: Mazaki Hitoshi , Watanabe Tadashi 
Published: July 2006

Abstract
Chlorophyll (Chl) a and its C-10 epimer, Chl a′, are compared for pheophytinization (demetallation) kinetics in aqueous acetone containing HCl. For each pigment the pheophytinization rate is of second order with respect to proton, and under identical conditions Chl a′ is pheophytinized by roughly 50% faster than Chl a, due probably to weaker Mg–N bonds in Chl a′.
1,3,4-Thiadiazolines by a 1,5-Dipolar Ring Reconstruction of Mesoionic (2,3-Diphenyltetrazolio)thio Ylides
Authors: Araki Shuki , Goto Tetsuya , Butsugan Yasuo 
Published: July 2006

Abstract
4-Phenyl-2-phenylazo-2,3-dihydro-1,3,4-thiadiazoles were synthesized from 2,3-diphenyltetrazolium-5-thiolate by two methods. The formation of the thiadiazolines is rationalized by 1,5-dipolar ring closure of the intermediate mesoionic (tetrazolio)thio ylides.
Preparation and Resolution of Bis[tris(2-aminoethaneselenolato)cobalt(III)-μ-Se, μ-Se′, μ-Se″]cobalt(III) Complex
Authors: Miyanowaki Shin , Konno Takumi , Okamoto Ken-ichi , Hidaka Jinsai 
Published: July 2006

Abstract
The title Se-bridged complex, [CoIII{CoIII(aese)3}2]3+ (aese=2-aminoethaneselenolate), was newly prepared by the reaction of fac-[Co(aese)3] with Co2+ and separated into three isomers, ΔΔ, ΔΛ, and ΛΛ, by the ion-exchange chromatographic method. The isomers were characterized from their absorption, CD, and 13C NMR spectra.
Ylide-Metal Complexes. XIV. An X-Ray Photoelectron Spectroscopic Study on Tellurium Complexes of Methylenetriphenylphosphorane
Authors: Konno Hidetaka , Yamamoto Yoshihisa 
Published: July 2006

Abstract
A series of new tellurium complexes of methylenetriphenylphosphorane, (C6H5)3P=CH2 (L), namely, dichlorobis(methylenetriphenylphosphorane)tellurium dichloride, [L2TeCl2]Cl2, chlorotris(methylenetriphenylphosphorane)tellurium trichloride, [L3TeCl]Cl3, and tetrakis(methylenetriphenylphosphorane)tellurium tetrachloride, [L4Te]Cl4, were examined by XPS. Binding energies of Te 3d electrons for the complexes are considerably lower than those for common Te(IV) compounds such as (C6H5)2TeCl2, TeCl4 (correctly Te4Cl16) and others, and they diminished with increasing number of L’s and decreasing number of bonded chlorine atoms, indicating that L is an electron donor. Bonded chlorine atoms and free chloride ions were clearly distinguished from the binding energy of Cl 2p3⁄2 electrons.
Determination of Iodide Ion Using Alkali-Free Lead Phosphate Glasses as Potentiometric Detector Sensors in Nonsuppressed Ion Chromatography
Authors: Nomura Tsuyoshi , Hikichi Yasuo , Nakagawa Genkichi 
Published: July 2006

Abstract
Alkali-free lead phosphate glasses containing silver oxide show a linear relationship with the Nernstian slope for iodide concentration. By using these glass membranes as potentiometric detector sensors for ion chromatography, the limit of detection for iodide ion was extended down to 0.05 μg cm−3. The high sensitivity can be interpreted in terms of the strong interaction between iodide ion and the silver ion incorporated in the membrane material.
Yeast-Mediated Reduction of N-Substituted Acetoacetamides. Improvement of Conversion by Immobilization
Authors: Kawai Masao , Tajima Kenji , Mizuno Satoko , Niimi Koichi , Sugioka Hiroaki , Butsugan Yasuo , Kozawa Akimasa , Asano Tsuneo , Imai Yoshio 
Published: July 2006

Abstract
N-Ethylacetoacetamide and acetoacetanilide were enantioselectively converted into the corresponding (S)-3-hydroxy compounds by alginate- or polyurethaneimmobilized bakers’ yeasts, while without immobilization the yield of the yeast-mediated reaction was very low.
Catalytic Oxygenation of Cholesterol with a Platinum Catalyst under Moderate Pressure of Oxygen
Authors: Sakamaki Hiroshi , Take Masa-aki , Akihisa Toshihiro , Matsumoto Taro , Ichinohe Yoshiyuki 
Published: July 2006

Abstract
The catalytic oxygenation of cholesterol 1 with a platinum black catalyst under moderate pressure (20–25 atm) of oxygen yielded eleven oxidation products, 3–13a. The reaction pathway of the catalytic oxygenation is discussed on the basis of the results for several reaction conditions.
Synthesis of 1,4-Benzoquinone Derivatives Having Two Side-Armed Polyethers and Crown Ethers, and Their Electrochemical Study in the Presence of Alkali Metal Cations (Na+ and K+)
Authors: Togo Hideo , Hashimoto Kiichi , Morihashi Kenji , Kikuchi Osamu 
Published: July 2006

Abstract
Several crown ethers and two side-armed polyethers which have reducible quinonoid groups were prepared. Some of them, 7a, 7b, and 7d, showed highly enhanced cation-binding properties for the Na+ cation upon electrochemical reduction.
A Facile Syntehsis of 2-Substituted Azetidines
Authors: Shono Tatsuya , Matsumura Yoshihiro , Uchida Kenshi , Nakatani Fumihiko 
Published: July 2006

Abstract
A new method for the synthesis of 2-substituted azetidines has been exploited. The method consists of (1) anodic acetoxylation of 1-(p-tolylsulfonyl)azetidine at the 2-position and (2) subsequent nucleophilic substitution of the acetoxyl group with nucleophiles such as trimethylsilyl cyanide, allyltrimethylsilane, 2-acetoxyfuran, and trimethyl phosphite.
Molecular Structure of Trimethylphosphine–Borane as Determined from Electron Diffraction and Microwave Spectroscopic Data
Authors: Iijima Kinya , Hakamata Yumi , Nishikawa Takashi , Shibata Shuzo 
Published: July 2006

Abstract
The molecular structure of trimethylphosphine–borane has been determined from gas electron diffraction and spectroscopic data. The molecular parameters and their uncertainties are rg(B–H)=1.225±0.011 Å, rg(P–B)=1.899±0.006 Å, rg(C–P)=1.815±0.003 Å, rg(C–H)=1.103±0.002 Å, ∠HBH=108.6±0.6°, and ∠CPC=104.6±0.3°. The P–B distance of this complex is about 0.04 Å shorter than those of trimethylphosphine–boron trihalides.
17O NMR Study of Metal Carbonyl Cluster Compounds. III. 17O NMR Spectra of Mixed Metal Carbonyl Cluster Compounds, R2Sn[M(CO)x][M′(CO)y], R2Sn[M(CO)x][M′(CO)yCp], and ClSn[Mn(CO)5][Fe(CO)2Cp]2
Authors: Onaka Satoru , Kato Yoshio 
Published: July 2006

Abstract
A series of mixed metal carbonyl cluster compounds of R2Sn[M(CO)x][M′(CO)y] and R2Sn[M(CO)x][M′(CO)yCp] were synthesized and their 17O NMR spectra were measured to demonstrate how 17O NMR spectroscopy is superior to IR spectroscopy to study the electronic nature of the oxygen atoms in CO groups. For these mixed metal clusters, 17O NMR spectral assignments were easily made and the electron distribution around the O atoms was concluded to be only slightly changed compared with those of homo-dinuclear R2Sn[M(CO)x]2 and R2Sn[M′(CO)yCp]2.
New Mesomorphic Compounds: N,N′-Dialkanoyl-2,4-bis(alkanoyloxy)-1,3-benzenediamines
Authors: Kawada Hiromitsu , Matsunaga Yoshio 
Published: July 2006

Abstract
A series of N,N′-dialkanoyl-2,4-bis(alkanoyloxy)-1,3-benzenediamines has been synthesized. The high temperature phases appearing in the heptanoyl to hexadecanoyl derivatives are viscous and are transformed into isotropic liquids with enthalpy changes of 20 kJ mol−1 or less. Their X-ray diffraction patterns are characteristic of the hexagonal disordered columnar phase. The second moment of the broad-line proton NMR spectrum measured in the mesophase region is 0.8 to 0.9 G2 in the case of the octanoyl derivative and 0.04 G2 in the case of the tetradecanoyl derivative, indicating the rather large difference in the motional behavior between these half-disk-shaped molecules.
Electrode Kinetics of Metal Complexes Confined in Perfluoro Polycarboxylate and Polysulfonate Coatings on Graphite Electrodes
Authors: Oyama Noboru , Ohsaka Takeo , Ushirogouchi Tooru , Sanpei Sachiko , Nakamura Sadako 
Published: July 2006

Abstract
A heterogeneous electron-transfer process of [Os(bpy)3]2+⁄3+ (bpy: 2,2′-bipyridine) and [(trimethylammonio)methyl]ferrocene/ferricinium (TAF+⁄2+) redox couples, which were confined in perfluoro polycarboxylate and polysulfonate polyelectrolyte coatings on graphite electrodes, at the electrode/film interfaces as well as a homogeneous charge-transport process within the coating films were examined by means of potential-step chronoamperometry and chronocoulometry, normal pulse voltammetry and ac impedance measurements. The relevant kinetic parameters (i.e., the standard rate constant k° and the transfer coefficient of the heterogeneous electron-transfer process and the apparent diffusion coefficient Dapp for the homogeneous charge-transport process) were determined at various concentrations of the redox species in the films at various pH’s. The temperature dependences of Dapp, k° and the formal potentials of the [Os(bpy)3]2+⁄3+ and TAF+⁄2+ couples confined in the films were also examined and the relevant activation parameters for the heterogeneous electron-transfer and homogeneous charge-transport processes and the reaction entropies of these redox couples were evaluated. On the basis of the kinetic and thermodynamic data obtained, the mechanism of the charge-transport process within the films, the effects of polymer domain and pH on the rates of the heterogeneous electron-transfer and homogeneous charge-transport processes and on the incorporation of the redox species into the films, etc. are discussed.
The α-Helical Conformation of the Aib-Containing Oligopeptide, Boc–(Leu3–Aib)2–OBzl
Authors: Okuyama Kenji , Tanaka Nobuo , Doi Masamitsu , Narita Mitsuaki 
Published: July 2006

Abstract
The octapeptide Boc–(Leu3–Aib)2–OBzl crystallizes in the space group P21, with a=11.450(2), b=27.915(7), c=11.255(2) Å, β=116.95(1)°, and Z=2. The crystal structure has been solved by direct methods and refined to an R value of 0.08. The peptide back-bone, except for the C-terminal Aib residue, folds into a right-handed α-helical conformation, stabilized by four intramolecular (5→1) hydrogen bonds and two intermolecular hydrogen bonds between molecules related by the 21 symmetry along the b direction. In order to determine the helical conformation definitively, the helical parameters (unit height h and unit twist θ) at each amino-acid residue were derived from the bond lengths, bond angles, and torsional angles of the peptide main chain. The average values of these parameters for seven residues (h=1.57 Å and θ=99.0°) showed much better agreement with those for an α-helix (h=1.5 Å and θ=100°) rather than with those for a 310-helix (h=2.0 Å and θ=120°). Peptide helices are arranged in columns in head-to-tail fashion. These columns are packed in parallel with respect to their helical direction. Between neighbouring chains of helices only hydrophobic contacts are found.
Biomolecules Conform to the Rule of Topological Charge Stabilization
Authors: Aihara Jun-ichi 
Published: July 2006

Abstract
Almost all biomolecules conform to the rule of topological charge stabilization. Heteroatoms are placed at the right sites in proteins, nucleoside bases, porphyrins, and related metabolites. It is noteworthy that typical redox-mediating coenzymes obey this rule both in the oxidized and reduced states. Thus, it is very likely that the rule of topological charge stabilization has been one of the most important guiding principles not only in chemical evolution but also in general biosynthesis.
The Infrared Spectrum of Dioxygen Bound to the Synthetic Porphinatoiron in an Aqueous Medium
Authors: Yuasa Makoto , Yamamoto Kimiko , Nishide Hiroyuki , Tsuchida Eishun 
Published: July 2006

Abstract
A highly concentrated aqueous solution of heme ([heme]=25 mM) was prepared by embedding the 5,10,15,20-tetrakis(α,α,α,α-o-(2′,2′-dimethyl-20′-(2″-trimethylammonio)ethylphosphonatoxy)eicosanamido)phenyl)porphinatoiron(II) complex of 1-dodecylimidazole in bilayer of polymerized 1,2-bis(2,4-octadecadienoyl)-sn-glycero-3-phosphocholine liposome (poly-lipid liposome/heme). The dioxygen-binding mode of the poly-lipid liposome/oxyheme in the aqueous medium was then measured by means of infrared difference spectroscopy: The νo–o value at 1161 cm−1 was found to correspond to those of the oxy picket-fence heme in Nujol mulls, oxy myoglobin, and oxy hemoglobin in an aqueous medium.
Ab Initio Calculation for the Interaction Energy of He–H
Authors: Ichihara Akira , Sasagane Kohtoku , Itoh Reikichi 
Published: July 2006

Abstract
Using the help of an ab initio calculation with a configuration interaction (CI) treatment, the potential energies of a HeH system in the ground (X2Σ+) and the first three (A2Σ+, B2Π, C2Σ+) excited electronic states were calculated, making due correction for the basis set superposition effect.
Geometrical Isomers of Anionic Complexes Favorable to Chiral Discriminatory Ion-Pairing with Λ-[Co(en)3]3+ Ion and the Diastereomeric Ion-Pair Formation Constants in Solution
Authors: Tatehata Akira , Asaba Yasuyuki 
Published: July 2006

Abstract
The stereoselectivities in the ion pairing of the geometrical isomers of anionic complexes, [Co(ox)(gly)2]− and [Co(ox)(edda)]− (ox=oxalate dianion, gly=glycinate anion, and edda=ethylenediamine-N,N′-diacetate dianion) with [Co(en)3]3+ have been investigated by a chromatographic method. Only the C1-cis(N) isomer of three geometrical isomers of [Co(ox)(gly)2]− and the β-cis isomer of two of [Co(ox)(edda)]−, in which three coordinated oxygen atoms are disposed triangularly along the pseudo C3 axis, have been observed to interact more strongly with [Co(en)3]3+ than the other geometrical isomers. The diastereomeric ion-pair formation constants of C1-cis(N)-[Co(ox)(gly)2]− and β-cis-[Co(ox)(edda)]− with [Co(en)3]3+ in solution have been determined by a conductance method at 25 °C. The results were consistent with those of the chromatographic studies. An enhancement of the circular dichroism (CD) intensity of the A2 component at the first d–d transition region of [Co(en)3]3+ has been observed upon the formation of ion pairing between the complex ions. Therefore, a favorable ion pair is considered to involve the hydrogen bonds between the coordinated oxygen atoms of the anionic complexes and the three N–H protons of [Co(en)3]3+ along the C3 axis.
Cobalt(III) Complexes with Quadridentate Ligands. VII. The Preparation and Properties of the Salicylato or Dichloro[tris(2-aminoethyl)amine]cobalt(III) Complexes and the Related Complexes
Authors: Toyota Eiko , Yamamoto Yutaka , Yamamoto Yoshihisa 
Published: July 2006

Abstract
Salicylato- or 3-methyl(or 4-methyl)salicylato[tris(2-aminoethyl)amine]cobalt(III) complexes, [Co(R-sal)tren]Cl·nH2O (R: H, CH3) have been prepared from a reaction mixture of dichloro[tris(2-aminoethyl)amine]cobalt(III) chloride hydrate, [CoCl2(tren)]Cl·H2O, Ag2O, and salicylic acid or 3-methyl- or 4-methylsalicylic acid. Two geometrical isomers (t- and p-) of their complexes were separated by Dowex 50W-X2 column chromatography. Their t- and p-isomers have been established by their 1H NMR and absorption spectra. The formation ratio of t- and p-isomers is ca. 3:1. The isomerization between t-isomer and p-isomer was not observed in water and methanol. In the absorption spectra, the first absorption band for the t- and p-isomers was observed at 535 nm and 515 nm, respectively. In the 1H and 13C NMR spectra of [CoCl2(tren)]Cl·H2O, the signals of the tertiary amine, (Remark: Graphics omitted.), side methylene protons and methylene carbons have been assigned to the individual methylene protons and methylene carbons of the coordinated tris(2-aminoethyl)amine ligand.
Voltammetric Study of Organic Metals. I. The Determination of the Electrochemical Conditions for Crystal Growth
Authors: Sakura Sachiko , Imai Hideo , Anzai Hiroyuki , Moriya Tetsuo 
Published: July 2006

Abstract
The metallic crystals of organic charge-transfer complexes are grown by means of the electrolytic oxidation of tetrathiafulvalene (TTF) derivatives in the presence of trihalide anions in organic solvents. In order to obtain a crystal of good quality, the optimal conditions for the growth have been searched for based on the data on the cyclic voltammetry. In this paper, the electrochemical conditions, such as the oxidation potential, the stability of the donor monocation radicals, and the redox behavior of the anions under the oxidation potential of the donors, are discussed in relation to the chemical reactions proceeding in the solution during the crystal growth.