Molar Ratio Of Base Research Articles

Molecularly engineered lignin to polyphenol via organocatalysis as an active sunscreen ingredient

Phenolation is one of the effective strategies to synthesize lignin-based polyphenols, improve lignin's properties, and extend its value-added applications in biological, medicinal and cosmetic fields. Herein, by taking the structural feature advantage of lignin, an effective and green strategy was developed to molecularly engineer lignin into a robust lignin-3-(2-hydroxyphenyl)propionate ester (LPPE) derivative via a transesterification reaction between 3,4-dihydrocoumarin (DHC) and the aliphatic hydroxyls in lignin under organocatalysis. The strategy is optimized and the novel derivative was systematically characterized by 1H, 13C and 31P nuclear magnetic resonance (NMR) and Fourier transform infrared (FT-IR) spectroscopy. The findings indicated that the successful introduction of 3-(2-hydroxyphenyl)propionate groups using a OH groups/DHC/organic base molar ratio of 1꞉1꞉0.3 at 120 °C for 6 h increased the content of phenolic hydroxyl groups from 1.793 1 to 3.017 9 mmol/g, and the LPPE exhibited excellent ultraviolet-absorbing and antioxidant performance with up to 90% free radical scavenging activity within 20 min using 5 mg/mL of LPPE. In addition, good biocompatibility and a high Sun protection factor (SPF) value of 40.9 were achieved at 5% (w) dosage of LPPE in the cream, indicating its significant application potential in sunscreen.

Recycling of multilayer packaging waste with switchable anionic surfactants

Switchable Anionic Surfactants (SAS) were used for delaminating flexible packaging waste composed of various plastic layers and aluminium, thereby promoting the recycling of such waste streams from a circular economy perspective. The delamination protocol was optimized on de-pulped food and beverage cartons containing low-density polyethylene (LDPE) and aluminium, varying the carboxylic acid and its counterion constituting the SAS (C8C18 carboxylic acids as the anionic part; inorganic bases and primary, secondary and tertiary amines as the cationic one) their molar ratio (carboxylic acid: base molar ratio from 1:1 to 1:3), SAS concentration (0.15, 0.3 and 0.5 wt%), time (0.5–3 h) and material weight in input (1–10 wt%). High-quality LDPE and aluminium were separated and recovered by using a diluted solution of a surfactant based on lauric acid and triethanolamine (C12-TEA), with performances not achievable with other anionic or cationic surfactants available on the market. The C12-TEA solution was then applied to a large variety of multilayer waste materials composed of polypropylene and aluminium, polyolefins/polyethylene terephthalate/aluminium, giving a material separation dependant on the structure and composition of the material in input. At the end of the process, lauric acid was recovered from the aqueous solution used for washing the separated materials by tuning its water solubility with CO2.

Thermo-switchable hydrophobic solvents formulated with weak acid and base for greener separation processes

Switchable solvents are changing properties when exposed to an external stimulus. As example, for thermomorphic multiphasic system (TMS), temperature changes can induce phase separations. Aqueous systems presented here are formulated with a carboxylic acid (weak acid) and an amphiphilic tertiary amine (weak base). They show thermo-switchable hydrophobicity and after separation, the weak acid and base are mainly found in the organic phase while the aqueous phase is mostly composed of water, up to 99 wt%. The phase separation temperature (cloud point) can be tuned from 20 to 80 °C depending on the choice of the carboxylic acid and on the acid: base molar ratio. A collection of saturated aliphatic carboxylic acids and benzoic acid derivatives have been investigated to evaluate the impact of different physico-chemical properties on the cloud point. The octanol/water partition coefficient (log P) and acidic constant (pKa) were identified as key physico-chemical properties to adjust the phase separation temperature. Finally, as illustration of the efficiency of these systems to remove a chemical from water, it has been shown that 99 % extraction of an anionic dye, methyl orange, could be achieved with most of the tested TMS.

A closer look at the synthesis of 2-[18F]fluoroethyl tosylate to minimize the formation of volatile side-products

Background2-[18F]Fluoroethyltosylate ([18F]FEtOTs) is a well-known 18F-fluoroalkylating agent widely used to synthesize radiotracers for positron emission tomography. The widespread use of [18F]FEtOTs is due in part to its low volatility when compared to other halide and sulfonate building blocks. In this work, the radioactive volatile side-products formed during the synthesis of [18F]FEtOTs were identified and characterized for the first time, and an optimization of the reaction conditions to minimize their formation was proposed.ResultsIn order to characterize the volatiles produced during [18F]FEtOTs synthesis, the reaction mixtures of both cold FEtOTs and [18F]FEtOTs were co-injected onto the HPLC system. The radioactive peaks corresponding to the volatile compounds were collected, analyzed through headspace gas chromatography mass spectrometry sampler (HS-GC–MS) and identified as vinyl fluoride ([19F]VF) and 2-fluoroethanol ([19F]FEOH). By using a rotatable central composite design with a two-level full factorial core of two factors (22), it was determined that temperature and time are independent variables which affect the generation of [18F]VF and [18F]FEOH during the radiosynthesis of [18F]FEtOTs. In addition, in order to reduce the formation of the volatiles ([18F]VF and [18F]FEOH) and increase the yield of [18F]FEtOTs, it was demonstrated that the molar ratio of base to precursor must also be considered.Conclusion[18F]VF and [18F]FEOH are volatile side-products formed during the radiosynthesis of [18F]FEtOTs, whose yields depend on the reaction time, temperature, and the molar ratio of base to precursor. Therefore, special care should be taken during the radiosynthesis and subsequent reactions using [18F]FEOTs in order to avoid environmental contamination and to improve the yield of the desired products.

Maastrichtian atmosphericpCO2 and climatic reconstruction from carbonate paleosols of the Marília Formation (southeastern Brazil)

AbstractPaleosols are the product of ancient physical, chemical, and biological processes on the Earth's surface and, as such, may record information that can be used to reconstruct the paleoatmospheric and paleoenvironmental conditions under which they formed. In Brazilian continental sedimentary successions, few studies using ancient soils have focused on the relationship between paleopedogenesis and paleoclimate. The Marilia Formation is a 160-m-thick section of the Bauru Basin in which ∼ 66% of the deposits show some evidence of pedogenic modification as paleosols. In this paper, paleosol profiles in the Marilia Formation containing thick calcrete intervals are described and attributed to three pedotypes: Avencas, Monte Alto, and Garça. Macro and microscopic pedogenic features of each pedotype are described in detail. Moreover, the analysis of clay mineralogy, whole-rock geochemistry, and stable-isotope composition are used to define pedogenic processes, paleoclimate proxies, and atmospheric pCO2 estimates. The Avencas pedotype is composed of six polygenetic profiles with different phases of carbonate precipitation, clay illuviation, and biogenic actions. The Monte Alto pedotype is moderately developed and composed of calcic horizons formed mainly by rhizoliths, with higher degrees of calcification and oxidation compared to Avencas profiles. The Garça pedotype is well developed with five polygenetic profiles presenting high carbonate content and low accumulation of clay minerals (CIA-K) and leaching. Estimates of paleoprecipitation and paleotemperature from the studied paleosols using climofunctions of molar ratio of base to alumina, depth of carbonate accumulation, salinization, oxygen composition, and paleosol weathering index proxy (PWI) show values ranging from 242 to 718 mm/yr and 11° to 14°, respectively. Climofunction values suggest a paleoclimate of semiarid to subhumid during deposition of the Marília Formation. The climate data also suggests that during the Maastrichtian, the Bauru Basin was geographically within the Southern Hot Arid Belt zone, though showing strong influence of the lower latitudinal Equatorial Humid belt. Furthermore, atmospheric pCO2 values calculated from pedogenic carbonates may correlate with a cooling interval during the latest Maastrichtian (68.5–66.25 My).

Influence of micellar size on the structure of surfactant-DNA complexes.

We have studied the structure of complexes of the cationic surfactant dodecyltrimethylammonium bromide (DTAB) with DNA as a function of surfactant to DNA base molar ratio (R) and salt concentration. Small-angle x-ray scattering data show the formation of nematic gels at lower and higher salt concentrations, irrespective of the value of R. Two crystalline phases are observed over intermediate salt concentrations; a square (S) phase for R>3 and a hexagonal (H_{S}) phase for lower R. Electron density maps of these phases show intercalated structures, with DTAB micelles sandwiched between long DNA strands. The composition of these complexes, estimated using elemental analysis, indicates that the micelles are not very long, and they occupy only about half of the interstitial volume between the DNA strands. This phase behavior is strikingly different from that of complexes of DNA with longer chain surfactants cetyltrimethylammonium bromide (CTAB) and tetradecyltrimethylammonium bromide (TTAB), which show only a hexagonal (H) phase over similar ranges of R and salt concentration, the H_{S} structure observed in the present study being a sqrt[3]×sqrt[3] superlattice of the H structure. Madelung energies of the S and H structures, calculated from the electrostatic interaction between their cylindrical constituents, suggest that the former is preferred in DTAB-DNA complexes due to the smaller micellar radius of DTAB. The propensity of DTAB to form short micelles seems also to favor the H_{S} phase at lower R. These results illustrate the important role of micellar size in determining the structure of these two-dimensional macro-ion crystals.

AlCl3‐Saturated Ionic Liquid Anolyte with an Excess of AlCl3 for Al–Graphite Dual‐Ion Batteries

AbstractAl–graphite dual‐ion batteries (AGDIBs) represent a compelling battery concept for large‐scale stationary storage of electricity in view of their safety, low cost, long cycling life, and high energy efficiency (80–90 %). However, at present, the deployment of AGDIBs is intrinsically limited by their low cell‐level energy density as a result of the non‐rocking‐chair operation principle and, consequently, the need for large quantities of acidic chloroaluminate ionic liquid (IL) anolytes as a reservoir of Al2Cl7− ions required for AGDIB operation. Thus far, AGDIBs have commonly employed IL anolytes with moderate acidity (AlCl3/Lewis base molar ratio of 1.3), which corresponds to charge‐storage anolyte capacity of ca. 19 mAh g−1, eventually resulting in low cell‐level energy densities of 20–30 Wh kg−1. In this work, we present an AGDIB utilizing an AlCl3‐saturated IL anolyte, containing an excess of AlCl3 powder for maintaining constant acidity during operation, leading to a theoretical capacity of 52 mAh g−1. The resultant AGDIB possesses an energy density of 59.1 Wh kg−1, along with a high energy efficiency of 85 % and an average discharge voltage of 1.71 V.

Nano-graphene oxide carboxylation for efficient bioconjugation applications: a quantitative optimization approach

A method for carboxylation of graphene oxide (GO) with chloroacetic acid that precisely optimizes and controls the efficacy of the process for bioconjugation applications is proposed. Quantification of COOH groups on nano-graphene oxide sheets (NGOS) is performed by novel colorimetric methylene blue (MB) assay. The GO is synthesized and carboxylated by chloroacetic acid treatment under strong basic condition. The size and morphology of the as-prepared NGOS are characterized by scanning electron microscopy, transmission electron microscopy (TEM), and atomic force microscopy (AFM). The effect of acid to base molar ratio on the physical, chemical, and morphological properties of NGOS is analyzed by Fourier-transformed infrared spectrometry (FTIR), UV–Vis spectroscopy, X-ray diffraction (XRD), AFM, and zeta potential. For evaluation of bioconjugation efficacy, the synthesized nano-carriers with different carboxylation ratios are functionalized by octaarginine peptide sequence (R8) as a biomolecule model containing amine groups. The quantification of attached R8 peptides to graphene nano-sheets’ surface is performed with a colorimetric-based assay which includes the application of 2,4,6-Trinitrobenzene sulfonic acid (TNBS). The results show that the thickness and lateral size of nano-sheets are dramatically decreased to 0.8 nm and 50–100 nm after carboxylation process, respectively. X-ray analysis shows the nano-sheets interlaying space is affected by the alteration of chloroacetic acid to base ratio. The MB assay reveals that the COOH groups on the surface of NGOS are maximized at the acid to base ratio of 2 which is confirmed by FTIR, XRD, and zeta potential. The TNBS assay also shows that bioconjugation of the optimized carboxylated NGOS sample with octaarginine peptide is 2.5 times more efficient compared to bare NGOS. The present work provides evidence that treatment of GO by chloroacetic acid under an optimized condition would create a functionalized high surface area nano-substrate which can be used for subsequent efficient bioconjugation applications.

Comparison of the hydrogen-bond patterns in 2-amino-1,3,4-thiadiazolium hydrogen oxalate, 2-amino-1,3,4-thiadiazole-succinic acid (1/2), 2-amino-1,3,4-thiadiazole-glutaric acid (1/1) and 2-amino-1,3,4-thiadiazole-adipic acid (1/1).

The X-ray single-crystal structure determinations of the chemically related compounds 2-amino-1,3,4-thiadiazolium hydrogen oxalate, C2H4N3S(+)·C2HO4(-), (I), 2-amino-1,3,4-thiadiazole-succinic acid (1/2), C2H3N3S·2C4H6O4, (II), 2-amino-1,3,4-thiadiazole-glutaric acid (1/1), C2H3N3S·C5H8O4, (III), and 2-amino-1,3,4-thiadiazole-adipic acid (1/1), C2H3N3S·C6H10O4, (IV), are reported and their hydrogen-bonding patterns are compared. The hydrogen bonds are of the types N-H···O or O-H···N and are of moderate strength. In some cases, weak C-H···O interactions are also present. Compound (II) differs from the others not only in the molar ratio of base and acid (1:2), but also in its hydrogen-bonding pattern, which is based on chain motifs. In (I), (III) and (IV), the most prominent feature is the presence of an R2(2)(8) graph-set motif formed by N-H···O and O-H···N hydrogen bonds, which are present in all structures except for (I), where only a pair of N-H···O hydrogen bonds is present, in agreement with the greater acidity of oxalic acid. There are nonbonding S···O interactions present in all four structures. The difference electron-density maps show a lack of electron density about the S atom along the S···O vector. In all four structures, the carboxylic acid H atoms are present in a rare configuration with a C-C-O-H torsion angle of ∼0°. In the structures of (II)-(IV), the C-C-O-H torsion angle of the second carboxylic acid group has the more common value of ∼|180|°. The dicarboxylic acid molecules are situated on crystallographic inversion centres in (II). The Raman and IR spectra of the title compounds are presented and analysed.

Specific features of nonstoichiometric interpolymer complexes of poly(acrylic acid) and poly(ethylene glycol) as protectors of copper nanoparticles in aqueous sols

Advantages of interpolymer complexes for use as amphiphilic protectors of nanoparticles during the formation and stabilization of sols are considered. The effects of the ratio of poly(acrylic acid) and poly(ethylene glycol) and the molecular mass of poly(ethylene glycol) on the mean size and size distribution of copper nanoparticles in sols formed via the reduction of divalent copper ions in mixed aqueous solutions of these polymers are investigated. It is shown that sols of metal nanoparticles with small sizes and narrow size distributions are formed even when poly(ethylene glycols) with chain lengths below the “critical” chain length and a small PEG-to-PAA base-molar ratio are used. This is evidence for efficient protection of the formed copper nanoparticles by the interpolymer complex PEG-PAA under conditions of its instability and for self-organization of oligomeric PEG chains in complex macromolecular shields of nanoparticles.

Polymorphous ZnO complex architectures: selective synthesis, mechanism, surface area and Zn-polar plane-codetermining antibacterial activity.

Complex ZnO architectures with tunable morphologies and structures were obtained by modulating only the base type and molar ratio of base to Zn2+ (α) using an easy one-pot hydrothermal approach without any template or organic additive. Characterizations by X-ray diffraction, Fourier-transform infrared spectrometry, scanning electron microscopy, transmission electron microscopy, and surface area analysis were performed. The effect of the base type and base/Zn2+ molar ratio on the morphology and corresponding mechanism were determined. The correlations between the microstructure and properties were established. The antibacterial effect of the ZnO samples was probably due to a combination of variable factors. Better antibacterial activity is derived from more effective antibacterial surfaces, which are mainly associated with the specific surface area and Zn-polar plane. Thus, flower-like architectures with larger specific surface areas and more highly exposed (0001) Zn-polar surfaces outwards are promising structures for ZnO antibacterial agents. This work provides a guide for devising and synthesizing highly efficient antibacterial materials.

Acid–Base‐Catalysed Condensation Reaction in Water: Isoxazolines and Isoxazoles from Nitroacetates and Dipolarophiles

Base-catalysed condensation reactions of nitroacetic esters with dipolarophiles to give isoxazole derivatives proceed faster, and often with higher yields, in the presence of water than in organic solvents such as chloroform. Kinetic profiles show that induction times are greatly reduced when the reaction is performed "in water" or "on water". Any specificity of the base related to H-bonding ability observed in chloroform is lost in water: all bases either organic or inorganic give the same result that is simply depending on concentration. A 0.1 molar ratio of base to nucleophile gives the best conversion, whereas addition of one equivalent of base or strong acid prevents the reaction from occurring. These results fit into a reaction sequence in which reversible addition to a dipolarophile is followed by acid-catalysed irreversible dehydration of the cycloadduct. This is a remarkable example of a condensation reaction occurring in water because of irreversible acid-catalysed water elimination. The reaction has been successfully applied to dipolarophiles containing a wide variety of functional groups, including carboxylic acids and ammonium salts, under mild conditions. This new click-style reaction is expected to be compatible with biological environments.

4,4'-Bipyridine-5-fluoro-isophthalic acid (1/1).

Co-crystallization of 5-fluoro­isophthalic acid (H2fip) with 4,4′-bipyridine (bipy) leads to the formation of the title compound [(H2fip)(bipy)], C8H5FO4·C10H8N2, with an acid–base molar ratio of 1:1. The acid and base subunits are arrange alternately in the crystal structure, displaying a wave-like tape motif via inter­molecular O—H⋯N and C—H⋯O hydrogen bonds [carbox­yl–pyridine synthon of R 2 2(7) hydrogen-bond notation], which are further combined into a two-dimensional architecture through C—H⋯F inter­actions involving the bipy and H2fip mol­ecules.

Interpolyelectrolyte Complexation in Chloroform

Interpolyelectrolyte complexes (IPECs) were formed in chloroform from complementary polyelectrolyte-surfactant complexes (PESCs), i.e., linear polyelectrolytes whose counterions were substituted by surfactants to dissolve them in the low-polarity organic solvent. The interaction between such complementary PESCs was followed by turbidimetry, (1)H NMR, and dynamic light scattering. The experimental results, together with those from transmission electron microscopy and scanning force microscopy, provide evidence on the formation IPECs in the system. This process is apparently driven by the entropically favorable release of the pairs of the oppositely charged surfactant ions. If the mixing base-molar ratio between the complementary PESCs, Z, is below a certain threshold value, their chloroform mixtures are colloidally stable, containing relatively large aggregates. These aggregates are attributed to particles of the formed IPECs stabilized by the fragments of the excess polymeric component. Otherwise, the mixtures of the PESCs undergo phase separation (most pronounced at Z = 1) with the formation of an insoluble top phase (attributed to insoluble IPEC) and a clear bottom phase enriched with the surfactant counterions. Electron and scanning force micrographs indicate a rather broad size distribution of the soluble macromolecular coassemblies with a close to spherical shape.

Nano-patterned structures in cylindrical polyelectrolyte brushes assembled with oppositely charged polyions

We demonstrate that the electrostatically driven association of cylindrical polyelectrolyte brushes (CPBs) with oppositely charged linear polyelectrolytes (PEs) in dilute aqueous solution gives rise to well-defined and colloidaly stable (not undergoing secondary aggregation with time) polymeric nano-assemblies representing novel water-soluble interpolyelectrolyte complexes (IPECs). Each complex particle comprises a single “host” CPB whose charge is undercompensated by the “guest” PE chains. Molecular dynamics (MD) simulations were used to probe the structural organization of these nano-assemblies. We find that they spontaneously adopt the shape of a necklace of complex coacervate pearls which comprise charged monomer units of CPB and those of the guest PEs in approximately stoichiometric (1:1) ratio. Each complex coacervate pearl is decorated by a star-like PE corona formed by the branches of the CPB not involved in the interpolyelectrolyte complexation. Repulsive interactions between these coronas stabilize the periodic intra-molecular structure and assure aggregative stability of the IPEC derived from the single CPB. AFM images of the complex particles deposited on mica unambiguously support their pearl-necklace structural organization. Our work theoretically predicts and experimentally confirms a possibility to tune the periodicity of one-dimensional intramolecular nano-patterned structures at will by a variation of the base-molar ratio between the oppositely charged macromolecular building blocks incorporated in the polymeric nano-assembly, that is, by a variation of the stoichiometry of the IPECs.

Dynamic Properties of Block Ionomer Complexes with Polyion Complex Cores

Reactions of polyion coupling and interchange were investigated using fluorescence quenching techniques in three systems: (1) soluble nonstoichiometric interpolyelectrolyte complex (IPEC) of poly(methacrylic acid) (PMA) and poly(N-ethyl-4-vinylpyridinium bromide) (PEVP), (2) block ionomer complex (BIC) of poly(ethylene oxide)-b-poly(methacrylic acid) copolymer (PEO-b-PMA) and PEVP, and (3) BIC of cross-linked ionic core PEO-b-PMA (#PEO-b-PMA) and PEVP. All measurements were done at the excess of the polyanion (base-molar ratio [PEVP]/[PMA] = 0.2). Rapid polyion coupling was observed following mixing the components in all three systems. However, unexpectedly, the rate of the polyion exchange and substitution reactions increased in the following order: IPEC < BIC < core cross-linked BIC. We posit that the free polyanion chain approaching and interpenetrating the polyion complex experiences greater electrostatic repulsion of the excess PMA units exposed at the IPEC surface compared to the PMA units hidden in the core of BIC. This may slow down the transfer of the PEVP chain from the IPEC to the free polyanion. Evidently, the steric repulsion of PEO chains in the BIC shell does not hinder the association of the reacting species or interpenetration and electrostatic coupling of the polyion chains.

Water-Soluble Complexes of Star-Shaped Poly(acrylic acid) with Quaternized Poly(4-vinylpyridine)

The interaction of star-shaped poly(acrylic acid) having various numbers of arms (5, 8, and 21) and a strong cationic polyelectrolyte, viz., poly( N-ethyl-4-vinylpyridinium bromide), was examined at pH 7 by means of turbidimetry and dynamic light scattering. Mixing aqueous solutions of the oppositely charged polymeric components was found to result in phase separation only if their base-molar ratio Z = [N+]/[COO (-) + COOH] exceeds a certain critical value ZM ( ZM < 1); this threshold value is determined by the number of arms of the star-shaped polyelectrolyte and the ionic strength of the surrounding solution. At Z < ZM, the homogeneous aqueous mixtures of the oppositely charged polymeric components contain two types of complex species clearly differing in their sizes, with the fractions of these species appearing to depend distinctly on the number of arms of the star-shaped poly(acrylic acid), the base-molar ratio of the oppositely charged polymeric components in their mixtures, and the ionic strength of the surrounding solution. The small complex species (major fraction) are assumed to represent the particles of the water-soluble interpolyelectrolyte complex whereas the large complex species (minor fraction) are considered to be complex aggregates.

Isoxazoles and Isoxazolines by 1,3‐Dipolar Cycloaddition: Base‐Catalysed Condensation of Primary Nitro Compounds with Dipolarophiles

Abstract1,4‐Diazabicyclo[2.2.2]octane (DABCO) or other suitable N‐bases cause primary activated nitro compounds to condense with alkenes to yield isoxazolines or with alkynes to give isoxazoles. As the molar ratio of the base with respect to the dipolarophile decreased, the reaction became slower, but the nitro compound became more resistant to hydrolytic cleavage. The best results were achieved with a molar ratio of base in the range of 0.05–0.1. The reactions were carried out in chloroform at 60 °C; for ethyl nitroacetate and phenylnitromethane, ethanol at 80 °C can be employed with better results and shorter reaction times. A catalytic cycle is proposed: in chloroform the hydrogen‐bonded ion pair formed between the nitronate and the protonated base undergoes reversible cycloaddition with the dipolarophile and then the hydrogen‐bonded intermediate adduct releases water by reaction with a second nitro molecule to give the product and the hydrogen‐bonded nitronate.(© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2007)

Role of Catalyst on Refractive Index Tunability of Porous Silica Antireflective Coatings by Sol−Gel Technique

Porous silica coatings were prepared by acid- and base-catalyzed sol−gel method. Surface morphology studies by atomic force microscopy showed smooth surface for acid-catalyzed coatings while base catalysis resulted in coarse particle morphology. On increasing the tetraethyl orthosilicate to base molar ratio from 1:1 to 1:3, the mean particle size of the coating shifted from 30 to 100 nm while the pore size varied from 4.7 to 14 nm. Infrared spectral analysis exhibited a change in the ratio of integrated peak intensities of Si−O−Si to Si−OH in acid-and base-catalyzed silica coatings. Textural studies showed an increase in particle size and porosity with base concentration. Optical transmission and surface roughness of base-catalyzed samples were found to be higher than that of acid-catalyzed silica coatings.

Asymmetric Hydrogenation of Acetonaphthone Catalyzed by RuCl2[P(C6H5)3]2-(R, R)-DPEN

Abstract A novel ruthenium complex RuCl 2 [P(C 6 H 5 ) 3 ] 2 -( R, R )-DPEN (DPEN = 1,2-diphenylethylenediamine) was synthesized, characterized by 1 H and 31 P NMR, and applied to the asymmetric hydrogenation of acetonaphthone. The effects of reaction temperature, hydrogen pressure, and molar ratio of base to catalyst on the activity and enantioselectivity were investigated in an isopropanol solution of (CH 3 ) 3 COK. The results showed that the increase in the temperature and pressure accelerated the reaction but slightly decreased the enantioselectivity for ( S )-α-naphthylethanol. Under the conditions of acetonaphthone:(CH 3 ) 3 COK:Ru = 50000:450:1 (molar ratio), 4 MPa, 25°C, and 16 h, 83% ee and 100% yield of α-naphthylethanol were achieved.