bluuebunny/crossref_metadata_2025_split huggingface dataset:
Generation of β-Keto Radicals from Cyclopropanol Derivatives by the Use of Manganese(III) 2-Pyridinecarboxylate as an Oxidant and Their Reactions with Olefins
Authors: Iwasawa Nobuharu , Hayakawa Satoshi , Isobe Koichi , Narasaka Koichi 
Published: May 2006

Abstract
Various β-keto radicals are generated from cyclopropanol derivatives such as 1- or 2-substituted cyclopropanols and a cyclopropanone hemiacetal by the use of manganese(III) 2-pyridinecarboxylate, and their reactions with electron-rich olefins give cross-addition products in good yields.
Tetrathio-Derivatives of p-Quinodimethanes Fused with 1,2,5-Thiadiazoles. A Novel Type of Organic Semiconductors
Authors: Yamashita Yoshiro , Tanaka Shoji , Imaeda Kenichi , Inokuchi Hiroo 
Published: May 2006

Abstract
Bis[1,2,5]thiadiazolo-p-quinobis(1,3-dithiole) (BTQBT) was prepared by a Wittig–Horner reaction of 2-dimethylphosphono-1,3-dithiole with the corresponding dione. BTQBT is a red-violet crystal with a high melting point and the conductivity is unusually high (10−3 S cm−1) as a single component. The X-ray structural analysis reveals that the molecule is completely planar and forms a sheet-like network by short S–S contacts.
Synthesis of Optically Pure 4-Hydroxymethyloxazolidinone as Chiral Serinol Synthon from Glycidol
Authors: Katsumura Shigeo , Kondo Akihiro , Han Qingjun 
Published: May 2006

Abstract
Optically pure 3-benzyl-4-hydroxymethyl-2-oxazolidinone and 4-benzoyloxymethyl-2-oxazolidinone as chiral serinol synthons were synthesized from optically active glycidol by intramolecular cyclization via 2,3-epoxycarbamates with strict SN2 behavior.
Monte Carlo Simulated Annealing Prediction for α-Helix Propensity of Amino Acid Homopolymers
Authors: Fukugita Masataka , Nakazawa Takashi , Kawai Hikaru , Okamoto Yuko 
Published: May 2006

Abstract
Monte Carlo simulated annealing calculation is carried out for various homopolymers of amino acid with 5–15 residues. Conspicuous α-helix propensity is found for poly-L-Met and poly-L-Lys. We also found that α-helices are hardly formed in poly-Gly and poly-L-Tyr. This α-helix propensity observed in the simulation is in excellent agreement with the empirical rule derived from synthetic homopolymers and from statistical analyses of peptide data bases.
Effect of Surface Treatment with CHClF2 on Catalytic Behavior of SiO2–Al2O3 and Al2O3
Authors: Kurosaki Akito , Okazaki Susumu 
Published: May 2006

Abstract
CHClF2 has been found to be effective as a surface treatment agent of SiO2–Al2O3 and Al2O3, as well as chlorofluorocarbons (CFCs) such as CCl2F2 and CClF3, to enhance its catalytic activity and/or activity maintenance for the alkylation of benzene with propene. The CHClF2-treatment may be performed at temperatures considerably lower than those required for CFC-treatments.
Bromine Addition to Rotameric 1-(9-Fluorenyl)-2-(1-methylvinyl)naphthalene. Fate of Intermediate Cations Produced by Bromine Cation Attack
Authors: Oki Michinori , Shionoiri Katsumi , Otake Katsumasa , Ono Masaru , Toyota Shinji 
Published: May 2006

Abstract
Treatment of the rotamers of the title compound with bromine afforded a normal addition compound in the case of ap, whereas the sp rotamer did bromo-olefins and a cyclic compound only. The results are discussed on the basis of the steric effects and π-participation of the fluorene ring in the case of sp that is not possible in the case of ap. Cation was produced from the bromine adduct of the sp form and the fate of the cation is disucssed by comparing with that of the ap.
Oxidative Addition of Chlorobenzene on an Iron-Cyclopentadienyl Cation to a Low-Valent Palladium Complex
Authors: Aoki Takanori , Ishii Youichi , Mizobe Yasushi , Hidai Masanobu 
Published: May 2006

Abstract
The oxidative addition of the coordinated chlorobenzene in [CpFe(C6H5Cl)][PF6] to Pd(PPh3)4 proceeds under THF-reflux conditions to give [CpFe{η6-[PdCl(PPh3)2]C6H5}][PF6]. X-Ray analysis of this complex revealed that the phenyl ring is σ-bound to Pd and π-bound to Fe, and that the palladium center takes the cis-configuration. This complex reacts with CO / MeOH, CO / HNEt2, styrene, and methyl acrylate to give methyl benzoate, N,N-diethylbenzamide, stilbene, and methyl cinnamate, respectively, after photolysis.
Rapid Self-Polycondensation of Amphiphilic Amino Acid Esters in Ordered Molecular Assemblies. An Morphological Evidence for Lateral Growth of Polypeptide at the Air–Water Interface
Authors: Miyasaka Tsutomu , Nishikawa Naoyuki , Hashimoto Kiyokazu , Ono Mitsunori 
Published: May 2006

Abstract
Monolayer-forming amphiphiles of amino acid esters, phenyl and 1,1-dichloroethyl esters of 2-aminoeicosanoic acid, underwent self-condensation to polypeptides in ordered monolayers with their reaction rates much higher than in non-ordered media. Scanning electron microscopy (SEM) revealed rapid progress of lateral polymerization at the air–water interface.
Trans Effect on the Rates of Rotation of the Axially Coordinated Imidazoles in Low Spin Iron(III) Porphyrin Complexes
Authors: Nakamura Mikio , Nakamura Nobuo 
Published: May 2006

Abstract
Rates of rotation of 2-methylimidazole, as studied by DNMR method, showed a drastic increase when the 6th ligand L′ in the porphyrin complex [(R-TPP)Fe(2-MeIm)(L′)]+Cl−was replaced by the less hindered ligands. The result was ascribed to the steric interactions between the 6th ligand and the ferric porphyrin part.
Fragmentation of Benzyl Esters with an Electron-Withdrawing Group by Photo-Induced Electron Transfer. Analogy with Fragmentation in Secondary Ion Mass Spectrometry
Authors: Ohashi Mamoru , Otani Shinju , Kyushin Soichiro 
Published: May 2006

Abstract
The analogy between negative secondary ion mass spectrometry and photo-induced electron transfer reactions has been seen in the fragmentation of radical anions of esters. The photochemical reaction may provide a new method of the protection of carboxylic acids.
The Effects of Diamine Skeleton and Its Substituents on Mesogenicity of Polyamides
Authors: Moriya Keiichi , Minagawa Tohru , Yano Shinichi 
Published: May 2006

Abstract
In the series of p-phenylene derivatives the monotropic nematic state was observed in poly(B-ODDA), poly(DMB-ODDA) and poly(CB-ODDA). No mesomorphic state was observed in poly(DCB-ODDA). The nematic state was observed in the series of diphenylmethane derivatives and the bulky alkyl substituent in the ortho position of the diphenylmethane heightens mesogenicity of the series of polyamides.
Methylene Bis(diisobutyldithiocarbamate) Neutral Carrier as Lead Sensing Material
Authors: Kamata Satsuo , Onoyama Kazuhiro 
Published: May 2006

Abstract
The sensitive and selective electrodes for lead(II) ion were developed by using the membrane based on methylene bis(diisobutyldithiocarbamate). The membrane electrode exhibited good response for Nernstian slope(28 mV/decade), linearity range(10−2–10−6 M) and selectivity factor of different metal ions, except for copper(II) ion.
Hydroxy Acid-Aided Synthesis of Perovskite-Type Oxides of Cobalt and Manganese
Authors: Teraoka Yasutake , Kakebayashi Hirofumi , Moriguchi Isamu , Kagawa Shuichi 
Published: May 2006

Abstract
The hydroxy acid-aided process using citric or malic acid produced a perovskite phase at relatively low calcination temperatures. The adjustment of the starting solution to an appropriate pH value in the malic acid-aided process resulted in reducing the temperature for the formation of single-phase perovskite-type oxides and in producing large surface-area oxides.
Palladium-Catalyzed Germylation of Organic Halides with a Digermane. Unexpected Formation of Germylene-Insertion Type Products
Authors: Reddy N Prabhakar , Hayashi Teruyuki , Tanaka Masato 
Published: May 2006

Abstract
Organic halides (RX) underwent dehalogenative germylation and germylene insertion type reactions with ClMe2GeGeMe2Cl in the presence of Pd(PPh3)4 as catalyst to give RGeMe2Cl and RGeMe2X respectively.
Molecular Recognition of Barbiturates by Diaminotriazine Functionalized Monolayers
Authors: Honda Yoshihiro , Kurihara Kazue , Kunitake Toyoki 
Published: May 2006

Abstract
Diaminotriazine functionalized amphiphiles were synthesized to form stable monolayers at the air-water interface. Combined examination of FT-IR, ESCA, and reflection absorption spectroscopies confirmed specific binding of barbituric acid and thiobarbituric acid to the monolayer, due to hydrogen bonding between the diaminotriazine head of amphiphiles and the imide moiety of barbiturates.
Reaction of [Mo3S4(H2O)9]4+ with Cobalt and Mercury. Syntheses and X-Ray Structures of Double Cubane-Type Cluster, [(H2O)9Mo3S4CoCoS4Mo3(H2O)9](CH3·C6H4·SO3)8·18H2O and Sandwich Cubane-Type Cluster, [(H2O)9Mo3S4HgS4Mo3(H2O)9](CH3·C6H4·SO3)8·2OH2O
Authors: Shibahara Takashi , Akashi Haruo , Yamasaki Mikio , Hashimoto Kohichi 
Published: May 2006

Abstract
Two new clusters, [(H2O)9Mo3S4CoCoS4Mo3(H2O)9](CH3·C6H4·SO3)8·18H2O (1) and [(H2O)9Mo3S4HgS4Mo3(H2O)9](CH3·C6H4·SO3)8·20H2O (2), have been synthesized by the reaction of [Mo3S4(H2O)9]4+ (3′) with metallic cobalt and mercury, respectively. The X-ray structure analyses revealed that in 1 two Mo3S4Co(H2O)9 moieties are joined through two cobalt-sulfur bonds, and in 2 a mercury atom was sandwiched by two 3′ s.
Biologically Active Novel Clerodane-type Diterpene Glycosides from the Root-stalks of Gleichenia japonica
Authors: Siddiqui Hamid L , Munesada Kiyotaka , Suga Takayuki 
Published: May 2006

Abstract
Two glycosides of a novel clerodane-type diterpene alcohol were isolated from the root-stalks of Gleichenia japonica (a fern; Urajiro in Japanese). Their structures were determined to be α-vinyl-1,2,3,4,4a,7,8,8a-octahydro-α,1,2,4a,5-pentamethyl-1-naphthalenepropanol 4-O-β-glucopyranoside and α-vinyl-1,2,3,4,4a,7,8,8a-octahydro-α,1,2,4a,5-pentamethyl-1-naphthalenepropanol 4-O-α-rhamnopyranosyl-(1→2)-β-glucopyranoside, respectively, by physicochemical methods. The former glycoside inhibited the growth of lettuce, while the latter one accelerated the growth.
New Approach to Chiral Conductive Materials. A Polymer Composite from Polypyrrole and an Optically Active Polyamide
Authors: Kato Takashi , Gondaira Masayuki , Amemiya Takashi , Fujishima Akira 
Published: May 2006

Abstract
A new conductive polymer composite retaining an asymmetric structure in the solid state has been prepared by electropolymerization of pyrrole in the presence of a chiral aromatic polyamide containing a sulfonic acid group. The composite exhibits conductivity of 0.5 S/cm.
Optical Humidity Sensor Using Nafion-Dye Composite Thin Films
Authors: Sadaoka Yoshihiko , Matsuguchi Masanobu , Sakai Yoshiro , Murata Yu-uki 
Published: May 2006

Abstract
By using NafionR film with crystal violet or pink FGHR, the optical humidity sensor has been fabricated. In the reflection mode, the optical intensity of the peak at 630 nm for crystal violet and at 540 nm for pink FGH decreases with relative humidity. The raising and recovery times are less than 1 min.
Microbial Transformation of sec-Hydroxyl Group of Polyols into Carbonyl Derivatives by Specific Oxidation Using Methanol Yeast
Authors: Matsumura Shuichi , Kawamori Tomoko , Yoshikawa Sadao 
Published: May 2006

Abstract
sec-Hydroxyl group of polyol was oxidized to the corresponding carbonyl derivative using methanol yeast, Candida boidinii KK912. Thus 1,2,4-butanetriol was oxidized for 2 days to give 1,4-dihydroxy-2-butanone in 78.1% yield. The microbial oxidation for analogous polyols was also discussed.
Asymmetric Hydrocyanation of 3-Phenoxybenzaldehyde Catalyzed by Poly(cinchona alkaloid-co-acrylonitrile)s
Authors: Danda Hidenori , Chino Kunitake , Wake Shigeo 
Published: May 2006

Abstract
Asymmetric addition of hydrogen cyanide to 3-phenoxybenzaldehyde catalyzed by poly(quinidine-co-acrylonitrile) affords (S)-2-hydroxy-2-(3′-phenoxyphenyl)acetonitrile in a moderate optical yield.
Highly Diastereoselective 1,4-Addition of Amines to Chiral α,β-Unsaturated δ-Lactone
Authors: Yoda Hidemi , Shirai Tsuyoshi , Kawasaki Tomoyasu , Katagiri Takao , Takabe Kunihiko , Kimata Kazuhiro , Hosoya Ken 
Published: May 2006

Abstract
Michael addition of amines to (S)-γ-amino-α,β-unsaturated δ-lactone was accomplished in extremely high diastereoselectivity with the ring-opening reactions and was disclosed to furnish (3R,4S)-diamino-hydroxyamides in high yields.
Potential-Time Profiles in the Initially Homogeneous Unstirred Belousov–Zhabotinskii Reaction with 2,3-Pentanedione
Authors: Tsukada Masao , Inamoto Naoki 
Published: May 2006

Abstract
Heterogeneities for concentration in the titled reaction have been studied using both platinum macro- and microelectrodes, and bromide ion selective macroelectrode.
Preparation of Highly Active Palladium Catalyst Supported on Silica by Ion Exchange Method
Authors: Fujitani Tadahiro , Echigoya Etsuro 
Published: May 2006

Abstract
Palladium catalyst supported on silica prepared by an ion exchange method using a low concentration of ammonia solution of PdCl2 exhibited high and stable activity in the hydrogenation of benzene. It was found that the activity and stability of the catalyst were strongly dependent on concentration of ammonia of the ion exchange solution.
Heterocyclic Betaines. Methylenepyridinium and Methyleneimidazolium Azolate Inner Salts. Synthesis and Structure
Authors: Alcalde Ermitas , Pérez Luisa , Fayet Jean Pierre , Vertut Marie Claire 
Published: May 2006

Abstract
A convenient synthesis of the hitherto unknown methylenepyridinium and methyleneimidazolium azolate inner salts is reported. Their structural characterization on the basis of the spectroscopic 1H and 13C NMR data and experimental dipole moments in the range of 12.34 to 15.34 Debye is discussed.
Radical Substitution on the Sulfur of Thioester Group. A Substituent Effect on the Reactivity of Thioesters to Methyl Radical
Authors: Tada Masaru , Hirokawa Toshiyuki , Tohma Tsutomu 
Published: May 2006

Abstract
Methyl radical reacts with thioesters (–S–CO–) to give methyl sulfide (CH3–S–), substitution products on sulfur. The mechanism is proposed in which the methyl radical attacks the sulfur in an nucleophilic manner in the rate determining step to give a sulfuranyl radical intermediate.
Diastereoselective Allylation of ω-Hydroxy Carbonyl Compounds by Allylic Alcohols with Pd–SnCl2
Authors: Takahara Jun P , Masuyama Yoshiro , Kurusu Yasuhiko 
Published: May 2006

Abstract
Allylation of ω-hydroxy carbonyl compounds by allylic alcohols with Pd–SnCl2 proceeded smoothly in neutral polar medium with high regio- and diastereocontrol via chelated bicyclic transition state.
Formation and X-Ray Crystal Structure of Charge-Transfer Complexes of Silacyclopentadiene Derivatives with Quinones
Authors: Kyushin Soichiro , Ohkura Yoshiyuki , Nakadaira Yasuhiro , Ohashi Mamoru , Yasui Masanori , Matsui Masaru , Iwasaki Fujiko 
Published: May 2006

Abstract
Silacyclopentadiene derivatives form charge-transfer complexes with various quinones which have been characterized by spectroscopic data and X-ray crystallographic determination.
Approach to De-NOx-ing Photocatalysis. Photocatalytic Decomposition of NO on Cu+/SiO2 Catalyst Prepared via Ion-exchange Method
Authors: Anpo Masakazu , Nomura Takaiki , Kitao Teijiro , Giamello Elio , Che Michel , Fox Marye Anne 
Published: May 2006

Abstract
Cu2+ ions supported onto SiO2 (Cu2+/SiO2) prepared by an ion-exchange method are reduced to Cu+ ions when the Cu2+/SiO2 sample is evacuated above 573 K. Cu+/SiO2 catalyst decomposes NO photocatalytically and stoichiometrically at 275 K. The excited state of the Cu+ ions plays a significant role in the photocatalytic decomposition of NO on the Cu+/SiO2 catalyst.
Acid-Catalyzed Photoreduction of Dialkyl Sulfoxides by an Acid-Stable NADH Analogue
Authors: Fukuzumi Shunichi , Tokuda Yoshihiro 
Published: May 2006

Abstract
Photoreduction of dialkyl sulfoxides by an acid-stable NADH analogue, 9,10-dihydro-10-methylacridine (AcrH2), proceeds in the presence of perchloric acid in acetonitrile via photoinduced electron transfer from the singlet excited state of AcrH2 to protonated sulfoxides to yield the corresponding dialkyl sulfides.
Enzymatic Synthesis of ω-Hydroxyalkyl and n-Alkyl β-D-Galactopyranosides by the Transglycosylation Reaction of β-Galactosidase
Authors: Matsumura Shuichi , Kubokawa Hiroo , Yoshikawa Sadao 
Published: May 2006

Abstract
ω-Hydroxyalkyl and n-alkyl β-D-galactopyranosides were directly prepared in high yield from 1,8-octanediol, 1,10-decanediol, 1-octanol and 1-decanol by the transglycosylation reaction of o-nitrophenyl β-D-galactopyranoside (ONPG) or lactose using β-galactosidase.
Synthesis and Structure of 1,10-o-Benzeno[2.2]orthocyclophane-o-quinones. Evaluation of Attractive Energy between Donor and Acceptor
Authors: Fukazawa Yoshimasa , Nakamura Tsuneyuki , Haino Takeharu , Usui Shuji 
Published: May 2006

Abstract
The title compounds were synthesized to evaluate the intramolecular charge transfer interaction between the donor (dimethoxybenzene) and the acceptor(o-benzoquinone) of defined arrangement.
A Novel Synthesis of Disubstituted 1,1-Difluoro-1-alkenes by Using 2,2,2-Trifluoroethyl p-Toluenesulfonate as a Difluorovinylidene Unit
Authors: Ichikawa Junji , Moriya Tsukasa , Sonoda Takaaki , Kobayashi Hiroshi 
Published: May 2006

Abstract
2,2,2-Trifluoroethyl p-toluenesulfonate is treated with lithium diisopropylamide and trialkylboranes successively to generate 1-alkyl-2,2-difluorovinylboranes, which in turn couple with aryl iodides in the presence of palladium catalyst and tetrabutylammonium fluoride to afford disubstituted 1,1-difluoro-1-alkenes in good yields.
Functional Derivatives of a New Ring System, 1H,4H-Azeto[2,1-b]thiazolo[3′,2′:1,5]pyrrolo[3,4-d][1,3]thiazine
Authors: Miskolczi István , Kövér Katalin E , Györgydeák Zoltán 
Published: May 2006

Abstract
The reaction of 7-β-phenylacetamido-3-formylceph-3-em-4-carboxylic acid benzhydryl ester with D-penicillamine gives rise to a new fused tetracyclic system.
Adsorption of AUCL4- by Kaolinites: Effect of pH, Temperature and Kaolinite Crystallinity
Authors: Hong Hanlie , Sun Zhenya , Fu Zhengyi , Min Xinmin 
Published: May 2006

AbstractAdsorption of the AuCl4− complex by kaolinites of different crystallinities (Kao-1 and Kao-2) from 100 mL of AuCl3·HCl·4H2O solutions containing 10,000, 500 and 50 µg/L Au and 1 g of kaolinite was measured at pH 3 to 9 at ambient temperature and 120°C. Adsorption from the 50, 500 and 10,000 µg Au/L solutions ranged from 64 to 100% at ambient temperature and from 68 to 100% at 120°C for both kaolinites. Adsorption was pH dependent with a maximum at pH <5 and a minimum at neutral and alkaline pHs. Up to 1 mg Au/g kaolinite was adsorbed by the kaolinites at both ambient temperature and 120°C. In a separate Au adsorption experiment using 100 mL of 4000 µg Au/L solutions and 0.02 to 1.0 g of Kao-1, up to 8.55 mg Au/ g of kaolinite was adsorbed. The pH dependence of Au adsorption suggests that surface complexation of Au to alumina sites at the edges of kaolinite particles might be involved. Protonation of kaolinite surface sites might facilitate adsorption of the anionic Au complex. Both kaolinites adsorbed ~100% of added Au at low pH values, but the less crystalline kaolinite (Kao-2) adsorbed more Au at high pH. Greater Au adsorption would be expected for the less crystalline Kao-2 sample if adsorption occurred at the edges of kaolinite particles.
Alteration of Kaolinite to Cancrinite and Sodalite by Simulated Hanford Tank Waste and its Impact on Cesium Retention
Authors: Zhao Hongting , Deng Youjun , Harsh James B. , Flury Markus , Boyle Jeffrey S. 
Published: May 2006

AbstractCaustic nuclear wastes have leaked from tanks at the US Department of Energy’s Hanford site in Washington State (USA) causing hundreds of thousands of gallons of waste fluids to migrate into the underlying sediments. In this study, four simulant tank waste (STW) solutions, which are high in NaOH (1.4 and 2.8 mol/kg), NaNO3 (3.7 mol/kg) and NaAlO2 (0.125 and 0.25 mol/kg), were prepared and reacted with reference kaolinite KGa-1 and KGa-2 at 50 and 80°C for up to 2 months. The structure and morphology of the resulting products were characterized using X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. The products were also examined for cation exchange and Cs+ sorption as a function of ionic strength and types of cations in the background solutions. Cancrinite and sodalite were the only new minerals observed in all of the conditions tested in this experiment. Two major chemical processes were involved in the reactions: dissolution of kaolinite and precipitation of cancrinite and sodalite. Increasing NaOH concentration and temperature, and decreasing NaAlO2 concentration increased the transformation rate. Both cancrinite and sodalite appeared stable thermodynamically under the experimental conditions. The newly formed feldspathoids were vulnerable to acid attack and pronounced dissolution occurred at pH below 5.5. Cancrinite and sodalite can incorporate NaNO3 ion pairs in their cages or channels. Sodium in cancrinite and sodalite was readily exchangeable by K+, but less easily by Cs+ or Ca2+. The feldspathoid products sorb nearly an order of magnitude more Cs+ than the unaltered kaolinite. The Cs adsorption is reduced by competing cations in the background solutions. At low ionic strength (0.01 M NaNO3 or 0.005 M Ca(NO3)2), Ca2+ was more competitive than Na+. When the concentration of the background solution was increased 10 times, Na+ was more competitive than Ca2+.
Preparation and Characterization of L-Aspartic Acid-Intercalated Layered Double Hydroxide
Authors: Yuan Qi , Wei Min , Wang Zhiqiang , Wang Ge , Duan Xue 
Published: May 2006

AbstractL-aspartic acid was intercalated into layered double hydroxides by coprecipitation. Two types of well crystallized material were obtained and were characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetry, differential thermal analysis and polarimetry. Schematic models of two intercalation structures with different basal spacings are given. It is proved that the optical activity of L-aspartic acid is retained during and after the intercalation process.
Si-Associated Goethite in Hydrothermal Sediments of the Atlantis II and Thetis Deeps, Red Sea
Authors: Taitel-Goldman Nurit , Bender Koch Christian , Singer Arieh 
Published: May 2006

AbstractThe properties of Si-associated goethite from sediments in the Atlantis II and Thetis Deeps in the Red Sea have been investigated in order to determine the effect of Si on the mineral. Two types of morphologies dominate in most samples: multi-domain crystallites, probably due to elevated Na concentration in the initial brine from which the mineral had crystallized, and mono-domain, acicular crystals. Goethite crystals with elevated Si/Fe elemental ratios are usually smaller and poorly crystalline, exhibiting numerous crystal defects, whereas larger crystals with higher crystallinity have lower Si/Fe elemental ratios. The higher Si/Fe ratios in Atlantis II Deep goethites and the lower ratio in Thetis Deep goethites probably reflect the levels of Si concentration in the hydrothermal fluids from which goethite precipitated. At relatively low Si/Fe ratios, the major effect of Si is to retard growth of the crystallites, but only a small number of defects are formed. At high Si/Fe ratios the defect concentration affects the properties of the crystals, as observed with Mössbauer spectroscopy. The Si association with goethite affects crystallinity and crystal size as indicated by X-ray diffraction, infrared spectroscopy and high-resolution transmission electron microscopy.