Boric Acid Esters Research Articles

Synthesis of oligomeric boron-containing phosphopolyols

Transesterification of phosphorus-containing esters of boric acid with glycols leads to formation of polyols, the promising antipyrenes. Structure and reactivity of the oligomeric boron-containing polyols are studied.

Boric acid esters as thermal stabilizers and fungicidal additives for elastomers from natural rubber

New and previously synthesized boric acid esters were studied as thermal stabilizing and fungicidal additives to elastomers based on natural rubbers.

An experiment study of hard coating and cutting fluid effect in milling aluminum alloy

This paper investigates the cutting performance of a tungsten carbide end mill with hard coating and a sulfurous boric acid ester cutting fluid in milling A6061P-T651 aluminum alloy. The experiments were conducted to compare the milling force responses and flank wear under various cutting conditions. The results indicate that adding sulfurous boric acid ester cutting fluid decreases tool wear by 12.5% for hard coating tungsten carbide end mills and decreases the milling force by 10%. Besides, the average values of side and end flank wear of TiAlN-surface multilayer end mills can be decreased 38.7% and 68.7% respectively compared with uncoated and dry end mills.

Effects of Novel Boric Acid Esters on Ion Transport Properties of Lithium Salts in Nonaqueous Electrolyte Solutions and Polymer Electrolytes

Three novel polymerizable anion receptors based on boric acid esters have been synthesized. The addition of these monomers appreciably enhanced the ionic conductivity of certain electrolyte solutions comprised of an aprotic organic solvent of low polarity and a lithium salt of low dissociation ability. Analysis of the viscosity and pulse-field-gradient spin−echo (PGSE) NMR results in association with the ionic conductivity data revealed that the conductivity enhancement originated from the increase in the degree of dissociation, resulting from the addition of these anion receptors. The 11B NMR spectra of dimethoxyethane electrolyte solutions with added boric acid ester monomers substantiated the finding that the ionic dissociation was facilitated by strong interaction between the Lewis-acidic anion receptor and Lewis-basic anions. The polymerizable anion receptor of the catechol borate derivative was cross-linked with a polyether macromonomer containing different lithium salts. The ionic conductivity could be correlated with glass transition temperatures of the polymer electrolytes by the WLF equation. The ionic conduction behavior of the boron polymer electrolytes was compared with that of the reference polymer electrolytes, and the lithium cation transference number was clarified to be higher for the former. The polymer electrolytes showed similar conduction behavior to that of the electrolyte solutions containing the anion receptor monomers.

Synthesis of a Lewis-acidic boric acid ester monomer and effect of its addition to electrolyte solutions and polymer gel electrolytes on their ion transport properties

A polymerizable anion receptor based on a boric acid ester was synthesized. When the anion receptor was added to different electrolyte solutions consisting of an aprotic solvent and a lithium salt, the ionic conductivity of certain electrolyte solutions, composed of low polar solvents or salts with low dissociation abilities, was enhanced appreciably. Viscosity measurements for the electrolyte solutions, with and without the added anion receptor, indicated that the conductivity enhancement was caused by an increase in the ionic dissociation due to the addition of the anion receptor. Pulse-field-gradient spin-echo (PGSE) NMR and 11B-NMR spectra supported that the ionic dissociation was facilitated by interaction between the Lewis-acidic anion receptor and Lewis-basic anions. The polymerizable anion receptor was crosslinked with a polyether macromonomer in different electrolyte solutions. Ionic conductivity of the resulting polymer gel electrolytes was also altered like that of the electrolyte solutions containing the anion receptor monomer.

Reaction of Stereoisomers of 5‐Isopropyl‐4‐methyl‐1,3‐dioxane with Esters of Monosubstituted Boric Acid.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Boric acid ester as an adhesion promoter for rubber compounds to brass-plated steel cord

The adhesion between a boric acid ester (BAE) containing rubber compound and a brassplated steel cord was investigated to understand the role of BAE as an adhesion promoter. An improvement in adhesion was shown with the low loading of BAE in the range 0.5-1 phr, while significant decline of adhesion was not observed with high loading at 2 phr and a long aging time of 15 days. The interphase between the brass plated steel cord and the rubber compound studied using Auger electron spectroscopy (AES) showed a stabilized adhesion interphase by BAE incorporation, resulting in the enhancement of the adhesion retention.

Application of Mechanochemical Catalysis to the Synthesis of Boric Acid Esters

The syntheses of triisopropyl borate and other boric acid esters under conditions of mechanochemical activation with the use of zeolite catalysts were found to be highly efficient. The proposed method exhibits the following advantages over known methods: short synthesis times, low energy consumption, higher yields of target products, and the absence of byproducts. The mechanism of the catalytic esterification of boric acid under conditions of mechanochemical activation is discussed.

Reaction of stereoisomers of 5-isopropyl-4-methyl-1,3-dioxane with esters of monosubstituted boric acid

Gas-liquid chromatography was used to establish that the reactivity of the cis isomer in the reaction of 5-isopropyl-4-methyl-1,3-dioxane with the diisobutyl ester of isobutylboric acid leading to the corresponding 1,3,2-dioxaborinane is greater than for the trans isomer. An AM1 calculation for the energy of the intermediate ions in this reaction with model derivatives of boric acids: dioxyborane and the dimethyl ester of methylboric acid showed that one of the probable reasons for the observed behavior is the lower barrier for conversion of the intermediate bipolar structure of the cis derivative in the step involving formation of the endocyclic B-O bond.

Effects of addition of a boric acid ester monomer to electrolyte solutions and gel electrolytes on their ionic transport properties

A novel boric acid ester monomer with polymerizable acryloyl group has been designed and synthesized. It is expected that the Lewis acidic nature of this monomer prefers interaction with salts in electrolyte solutions and in polymer gel electrolytes. When the boric acid ester monomer was added to various electrolyte solutions, both of the solubility of salts and ionic conductivity of the solutions were increased considerably. The boric acid ester monomer was polymerized to fix it to the matrix polymer of gel electrolytes. The ionic conductivities of the gel electrolytes increased as compared to those without the boric acid ester monomer. The conductivity enhancement effect was greater for the polymer gel electrolytes than for the electrolyte solutions.

Boric Acid Esters as Fungicide Additives and Heat Stabilizers of Elastomers Based on Siloxane Rubber

New boric acid esters with an azomethine bond were prepared. These compounds exhibit an efficient fungicide and heat-stabilizing effect on elastomers based on SKTV-1 rubber.

A Preparative Method for Perfluoroalkyltrifluoroborates and Perfluoroalkyldifluoroboranes

A convenient new preparative method for the unknown class of perfluoroalkyltrifluoroborates K[CnF2n+1BF3] and perfluoroalkyldifluoroboranes CnF2n+1BF2 (n > 1) is elaborated. The perfluoroalkyl group is introduced into the boric acid ester by using CnF2n+1MgBr. Treatment with K[HF2] and HFaq results in K[CnF2n+1BF3] which can be defluoridated by AsF5 to the corresponding boranes CnF2n+1BF2.

Conformational analysis of 5-methyl-4-phenyl-1,3,2-dioxaborinane stereoisomers

It is known that molecular conformation of cyclic boric acid esters largely depends on the nature of B-O bonds; thus for 1,3,2-dioxaborinane, the chair conformer, characterized by the maximum p--r~ interaction of the n-electron pairs of oxygen and the vacant orbital of boron, is the most stable form [1]. However, in the asymmetrically substituted derivatives, as shown for 4,5-dimethyl-l,3,2-dioxaborinane, this conformation may be distorted, giving rise to a family of half-chair forms [2]. This work is a continuation of our studies on stereochemistry of cyclic boric esters with several chiral centers in the carbon section of the cycle. Here we examine in detail the conformational composition of 2-isobutyl-5-methyl-4-phenyl1,3,2-dioxaborinane (I) stereoisomers using 1H NMR spectroscopy as well as empirical (MM2) and semi-empirical (AMI) calculations of the optimal geometry. Experimental. The IH NMR spectrum of a mixture of stereoisomers of I was measured on a Bruker AM-300 spectrometer (operating frequency 300 MHz) for a 5% CDCI 3 solution of the sample (TMS as internal standard). Synthesis of I was described in [3, 4]. The energies of the cis and trans conformations of model 5-methyl-4-phenyl-l,3,2-dioxaborinane (Ia) were calculated with full geometry optimization by the empirical (MM+) [5] and semi-empirical (AMI) [6, 7] methods using the HyperChem 5.02 package [8]. Results and Discussion. The parameters of the 1H NMR spectrum of a 80:20 mixture of stereoisomers I as well as the corresponding data for 2-isopropyl-4,5-dimethyl-l,3,2-dioxaborinane (II) [9] are shown in Table 1. The protons at the ring carbon atoms form a spin system AA'BX. All components of the system are isolated and informative for both isomers. The multiplet of the methylene protons of the ring at the C 6 atom of the minor isomer as well as the spin-spin coupling constants (SSCC) 3JAx and 3JBx are similar to the corresponding characteristics observed in the spectra of 5-methyl-l,3,2-dioxaborinane [1] and trans II and suggest that the orientation of the methyl group at the C 5 atom is

Properties of vapor-deposited borophosphorosilicate glass layers employed in technology of silicon integrated circuits

The data of investigations on the physicochemical and electrophysical properties of borophosphosilicate glass layers deposited from mixtures of tetraethoxysilane and esters of boric and phosphoric acids in an oxygen-ozone medium (temperature, 400–440°C; atmospheric and subatmospheric pressures) have been generalized. The empirical relationships are obtained for determining the boundaries of the optimum dopant concentration region when the glass is used as a reflow interlayer dielectric in integrated circuit technology. The assumption is made that the structure of borophosphosilicate glass layers is formed by a porous network involving dopant clusters.

Synthesis of 3-perfluoroalkyl-propyl esters of L-(+)-tartaric acid

A convenient and effective method for the preparation of perfluoroalkyl-propanols (F–(CF 2) n –(CH 2) 3–OH, n = 6,8,10) via boric acid esters is described. The radical addition of F-alkyl iodides to the CC double bonds of triallyl borate is followed by the reduction step using tributylstannane hydride under one-pot conditions. Finally, the mild aqueous deprotection of the alcoholic function completes the reaction with an overall yield of 75–79%. The fluorophilicity ( f) values of these and some other fluoroalcohols, which describe their phase preference, were determined by gas chromatography. F-alkyl-propanols are useful synthetic precursors of fluorinated esters of L-tartaric acid—potential chelating agents in fluorous biphase transformations.

Stereochemistry of the formation of 2-alkyl-4,5-dimethyl-1,3,2-dioxaborinanes

It is demonstrated with the help of1H and13C NMR spectroscopy and GLC that the formation of the stereoisomers of 2-alkyl-4,5-dimethyl-1,3,2-dioxaborinanes from 2-methyl-1,3-butanediol and acyclic boric acid esters occurs stereospecifically. This conclusion was confirmed by calculations of the optimal geometries and relative energies of the molecules of thecis-andtrans-isomers of model 4,5-dimethyl-1,3,2-dioxaborinanes and the proposed intermediate with a tetravalent boron atom using the method of molecular mechanics.

A Novel Electrolyte Solvent for Rechargeable Lithium and Lithium‐Ion Batteries

We describe a new type of electrolyte solvent which provides remarkable improvement in properties of electrolyte systems containing it. These solvents contain acidic boron atoms, in most cases linked into heterocycles by reaction of boric acid, or oxide, with glycols. Nicknamed BEG solvents (for boric acid esters of glycol), these show great propensity for dissolving salts, stabilizing alkali metals against corrosion, and in some cases, stabilizing other solvents (particularly alkene carbonates), against anodic decomposition. In the most favorable case so far, the 1,3 propylene glycol boric acid ester (BEG‐1) which contains two linked borate groups, the mixed solvent formed by mixing 1 part BEG‐1 with two parts ethylene carbonate provides an electrochemical stability window in excess of 5.8 V (cf. 4.5 V for ethylene carbonate alone with the same salt), an ambient temperature conductivity of with 1 m , and enduring stability against metallic Li, which remains shiny on prolonged (days) immersion at 100°C. We present data on various electrolyte solutions containing these components and then show their utility in devices by rubberizing them with polymers and constructing voltaic cells Li/, which show excellent charge/discharge characteristics and cyclability.

Asymmetric synthesis of highly functionalized tetracyclic indole bases embodying the basic skeleton of yohimbine- and reserpine type alkaloids

Schiff bases derived from tryptophan methyl ester react with differently substituted electron-rich siloxy dienes in the presence of achiral or chiral boric acid esters to give enaminones 5 and 6 with high diastereomer ratios (up to >98:2). These intermediates are converted into highly functionalized indoloquinolizines 14 and 15 by means of a new method which employs the transformation of vinylogous amides to vinylogous chloromethyl amines and their subsequent conversion to vinylogous imidoyl chlorides as the key step.

Novel model system to study the influence of rubber compound formulation on the structure and composition of the rubber–brass interphase

AbstractA model system was developed to study the influence of the rubber formulation and/or the aging conditions on the adhesion between brass and rubber. The bonding compounds were vulcanized on thin, homogeneous brass layers that had been prepared by sputtering onto special polymeric substrates; some of these compounds were steam‐aged under controlled conditions subsequently. After the separation of the polymeric film, combined analytical electron microscopy (transmission electron microscopy/energy dispersive spectroscopy; TEM/EDS) and sputter neutral mass spectrometry (SNMS) analyses were performed. While the TEM/EDS studies offer a detailed insight into the morphological structure of the interphase, the SNMS depth profiles allow a rapid and reliable differentiation between various rubber formulations. With these model samples the beneficial effect of boric acid esters on the adhesion of cobalt‐containing bonding compounds, which is observed in a typical short‐term adhesion test after steam‐aging, can be explained: boric acid esters act with cobalt salts as corrosion inhibitors for brass, preventing the growth of a thick intermediate ZnO/Zn (OH)2 layer that is the starting point for delaminations.

Fractional analysis of technical polyoxaalkyl borates by TG

Results of preliminary thermoanalytical investigations (DSC/TG) of polyoxaalkyl esters of boric acid are presented. One aim of these investigations was the development of a method of characterization of the technical esterificate. The optimum parameters of quantitative thermogravimetric analysis of boric acid esters and the excess of polyoxaalkanols were assumed. The precision and accuracy of the developed method are discussed.