Synthesis of a New Polyoxometalate Loaded Stearic Acid Nanoparticles

The stearic acid nanoparticles loaded polyoxometalate K6[γ-(CpTi)2SiW10O38][(CpTi)2SiW10] have been prepared and structurally characterized by elemental analysis, IR spectra.The particle size was estimated by transition electron microscope and zatesizer instrument. The result showed that the polyoxometalate retained the parent structure after encapsulation by stearic acid nanoparticles.     

Corrosion Inhibition of a Green Scale Inhibitor Polyepoxysuccinic Acid

The corrosion inhibition of a green scale inhibitor, polyepoxysuccinic acid (PESA) was studied based on dynamic tests. It is found that when PESA is used alone, it had good corrosion inhibition. So, PESA should be included in the category of corrosion inhibitors. It is not only a kind of green scale inhibitor, but also a green corrosion inhibitor. The synergistic effect betweenPESA and Zn2 or sodium gluconate is poor. However, the synergistic effect among PESA, Zn2 and sodium gluconate is excellent, and the corrosion inhibition efficiency for carbon steel is higher than 99%. Further study of corrosion inhibition mechanism reveals that corrosion inhibition of PESA is not affected by carboxyl group, but by the oxygen atom inserted. The existence of oxygen atom in PESA molecular structure makes it easy to form stable chelate with pentacyclic     

Can an Amine Be a Stronger Acid than a Carboxylic Acid? The Surprisingly High Acidity of Amine–Borane Complexes

The gas‐phase acidity of a series of amine–borane complexes has been investigated through the use of electrospray mass spectrometry (ESI‐MS), with the application of the extended Cooks kinetic method, and high‐level G4 ab initio calculations. The most significant finding is that typical nitrogen bases, such as aniline, react with BH₃ to give amine–borane complexes, which, in the gas phase, have acidities as high as those of either phosphoric, oxalic, or salicylic acid; their acidity is higher than many carboxylic acids, such as formic, acetic, and propanoic acid. Indeed the complexation of different amines with BH₃ leads to a substantial increase (from 167 to 195 kJ mol^?1) in the intrinsic acidity of the system; in terms of ionization constants, this increase implies an increase as large as fifteen orders of magnitude. Interestingly, this increase in acidity is almost twice as large as that observed for the corresponding phosphine–borane analogues. The agreement between the experimental and the G4‐based calculated values is excellent. The analysis of the electron‐density rearrangements of the amine and the borane moieties indicates that the dative bond is significantly stronger in the N‐deprotonated anion than in the corresponding neutral amine–borane complex, because the deprotonated amine is a much better electron donor than the neutral amine. On the top of that, the newly created lone pair on the nitrogen atom in the deprotonated species, conjugates with the BN bonding pair. The dispersion of the extra electron density into the BH₃ group also contributes to the increased stability of the deprotonated species.     

Lewis Acid Modulation in a Amido-functional Diarylethene and Its Hypsochromism Effect

A photochromic diarylethene,1,2-bis(2-methyl-5-(4-N,N-dimethylaminophenyl)thien-3-yl)perfluorocyclopen-tene in proton-donating media was studied.The ammonium salt came into being in the presence of acetic acidfollowing localization of lone pair electrons of the amino group.The maximum absorption of the salt had a 36 nmhypsochromic shift,and its molar extinction coefficient increased to 3.494×10~4 L·mol~(-1)·cm~(-1).The conjugationaland delocalizational energy levels were calculated by Gaussian 98,and its hypsochromic shift mechanism was alsodiscussed.     

L-α-Aminoadipic Acid from L-Glutamic Acid

A convenient procedure for the preparation of L-α-aminoadipic acid from L-glutamic acid is described.     

Sulfamic Acid as a Cost-effective Catalyst for Acetolysis of Cyclic Ethers

Sulfamic acid has been used as an efficient catalyst and green alternative for conventional acidic materials to promote the acetolysis reaction of THF to produce 1,4-diacetoxybutane. This method is also applicable in the acetolysis of other cyclic ethers, such as methyl substituted THF and tetrahydropyran and 1,4-dioxane which is less reactivity.     

Structure of an Extracellular Polysaccharide from a Strain of Lactic Acid Bacteria

A new extracellular polysaccharide (EPS-I) isolated and purified from Z222, a strain of Lactic acid bacteria has been investigated. Sugar composition analysis, methylation analysis and ^1H NMR and ^13C NMR spectroscopy reveal that the EPS-I is composed of a pentasaccharide repeating unit. The sequence of sugar residue was determined by using two-dlmensional NMR spectroscopy, including heteronudear multiple-bond correlation(HMBC) and nuclear overhauser effect spectroscopy (NOESY).     

O-Benzenedisulfonimide as a Reusable Brønsted Acid Catalyst for Hetero-Michael Reactions

The hetero-Michael reactions among various oxygen, sulfur, and nitrogen nucleophiles and α,β-unsaturated compounds were carried out in the presence of catalytic amounts of o-benzenedisulfonimide as Brønsted acid organocatalyst. The reaction conditions were very mild, and the yields of target products were good. The catalyst was easily recovered and purified, ready to be used in further reactions. This ability grants economic and ecological advantages.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Catalytic Conversion of Isopropanol on a Heteropoly Acid–η-Aluminum Oxide System

Russian Journal of Physical Chemistry A - The results from catalytic conversion of isopropanol on a heteropoly acid–η-aluminum oxide system are discussed. It is established that...     

Terminalic Acid, a New Tannin from the Fruit of Terminalia chebula

AsatheraPeuticherbusedintraditionalChinesemedicine,TerminaliachebulaisconventionallygrowninGuangdong,Guangxi,andtheYunnanprovinceofChina.Itsripefruitisefficaciouslycurativewhenusedintreatingdiarrheaandhoarsenessofthethroatandcanalsobeusedasanastringenttobringabouthemostasisortoremovesomepathogenic"internalheat"ortoxicelementsfromwithinhumanphysique'.SeveralstudiesonhydroIysabletanninswithchebuloylgrouphavebeenreportedsofar2.AspartofaprogramforasystematicstudyofTchebula,wehavesuccessfullyis…     

Thermochemical Study of Acid—Base Reactions in a Glycyl-Tyrosine Aqueous Solution

Thermal effects of the interaction between a glycyl-tyrosine solution and solutions of HNO₃ and KOH in different pH ranges at a temperature of 298.15 K and ionic strengths of 0.25, 0.5, and 0.75 (KNO₃) are measured via calorimetry. Thermal effects of the stepwise dissociation of the dipeptide are determined. Standard thermodynamic characteristics Δ_rH°, Δ_rG°, and Δ_rS° of acid—base reactions in aqueous solutions of glycyl-tyrosine are calculated. The relationship between the thermodynamic characteristics of dipeptide dissociation and the structure of this compound is examined.     

Synthesis and Crystal Structure of a Hexameric Organooxotin Cluster from Benzilic Acid

1 INTRODUCTION There is great interest in the study of organotin carboxylic ester compounds due to their consider- able biological activities and structural diversities[1~3]. Since Holmes, R. R.[4] first reported the hexameric drum organotin compound, many organotin carboxy- lic ester compounds with drum-shape have been syn- thesized in recent years[5, 6]. It has been revealed that organotin compounds containing carboxylate ligands with additional donor atoms that are available for coord…     

Preparation and Kinetics of a Novel Glutathione Peroxidase Mimic- Selenium-modified Hyaluronic Acid

A selenium-modified hyaluronic acid（HA） compound（SeHA） was synthesized as a mimic of glutathione peroxidase（GPX）. IR and NMR spectra of SeHA predict that the --CH2OH group of the N-acetyl-D-glucosamine in HA was modified by group --Sell. There are averagely 152 --Sell groups in one SeHA molecule. The GPX activities are 103.88, 32. 15 and 152. 71 U/μmol, respectively, when the substrates were H2O2, BuOOH and CuOOH. Ping-pong mechanism was observed in the steady-state kinetic studies of the reactive oxygen species（ROS） consuming reaction. Result of reactions of SeHA with free radical capturer 2,6-di-tert-butyl-4-methylphenol（BHT） shows that the catalysis is based on a non-free radical-mechanism and the SeHA can not be inhibited by iodoacetate, an enzyme inhibitor.     

One-Pot Synthesis of 2,5-Furandicarboxylic Acid from 2-Furoic Acid by a Pd-catalyzed Bromination–Hydroxycarbonylation Tandem Reaction in Acetate Buffer

The one-pot synthesis of 2,5-furandicarboxylic acid from 2-furoic acid with a yield of 57 % was achieved for the first time using a Pd-catalyzed bromination-hydroxycarbonylation tandem reaction in HOAc-NaOAc buffer. This synthetic protocol shows major improvements compared to previously reported methods, such as using biomass-based 2-furoic acid as low-cost raw material, one-pot synthesis without isolation of intermediate products, and no need for an acidification procedure. Experiments indicate that the involved Xantphos-modified Pd-catalyst and the buffer solution play significant promoting roles for each individual reaction whereas Br₂ (as the brominating reagent) had a negative effect on the second hydroxycarbonylation step, while CO was deleterious for the first bromination step. Hence, in this practical one-pot synthesis, Br₂ should be consumed in the first bromination step as fully as possible, and CO is introduced after the first bromination step has been completed.     

2-Hydroxyphenylphosphinic Acid: P-Analogue of Salicylic Acid?

Abstract

Substitution of the carboxyl group -C(O)OH by -P(O)(OH)₂ and -P(O)R(OH) leads to compounds of interest to agriculture, technics and pharmacology. Under these aspects the P-analogon 1 of salicylic acid was prepared, because the monobasic -P(O)H(OH) group resembles more the carboxyl function than the dibasic moiety -P(O)(OH)₂.     

An Efficient Procedure for Esterification of Aryloxyacetic Acid and Arylthioacetic Acid Catalyzed by Silica Sulfuric Acid

Aryloxyacetate and arylthioacetate are wildly used in herbicides, plant regulator and insecticides. Recently, Wille et al. have reported that methyl aryloxyacetate is an efficient agent to prevent and treat allergic contact dermatitis.[1] The most popular synthesis is by heating sodium phenoxide (mercaptide) with ethyl chloroacetate in DMF,[2] or by the esterification of acid with alcohol using concentrated H2SO4 as catalyst.[3] In this paper, synthesis of aryloxyacetate and aryl thioacetate from aryloxyacetic acid and arylthioacetic acid respectively in ether catalyzed by silica sulfuric acid in 83%～94% yields is described. The catalyst is reused for 3 times without significant loss of activity (Entry 4). Compared with common procedures, the present procedure possesses the advantages of the operational simplicity, short reaction time,less-corrosion, high yield and reusable catalyst.     

The Electrochemical Behavior of p-Aminophenol at a ω-Mercaptopropionic Acid Self-Assembled Gold Electrode

A -mercaptopropionic acid (MPA) self-assembled monolayer modified electrode (MPA/SAM/Au) on a gold electrode has been fabricated. The characterization of the MPA/SAM/Au was investigated using attenuated total reflection-fourier transform infrared (ATR-FTIR) and A.C. impedance. The electrochemical behaviors of p-aminophenol (p-AP) were studied at the MPA/SAM/Au by cyclic voltammetry and semi-derivative voltammetry (SDV) in BR buffer solution. The modified electrode shows excellent electrocatalytic activity for the redox of p-AP and accelerates the electron transfer rate. The diffusion coefficient (D) is 4.55×10^–6cm²s^–1. The oxidative peak current increases linearly with the concentration of p-AP in the range of 4.0×10^–88×10^–6molL^–1 and 1.0×10^–52×10^–4molL^–1 by square wave voltammetry response, respectively. The detection limit (three times the signal blank/slope) is up to 1.2×10^–8molL^–1. The modified electrode is able to eliminate the interference of p-benzenediol, o-benzenediol and o-AP at a 40-, 90- or 70-fold concentration of p-AP, and it has been satisfactorily used for the determination of the real sample.     

Propanephosphonic Acid Anhydride–Mediated Cyclodehydration of Maleic Acid Monoamides

Propanephosphonic acid anhydride (T3P) has been proposed as a novel reagent for the preparation of maleic acid isoimides from the corresponding monoamides. A series of substituted aromatic and aliphatic isoimides have been prepared in good yields. The main advantage of this synthetic method is the use of environmentally benign, cost-efficient reagents and solvents, which are also safer to handle than the ones employed previously.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Improving the Selectivity of the Phosphoric Acid β-Elimination on a Biotinylated Phosphopeptide

This study aims at improving the MALDI-TOF detection of a phosphorylated peptide containing a cysteine residue by ??-elimination of H₃PO₄ hardly enriched by classical methods. The experimental conditions were optimized on this phosphopeptide (biot-pAdd) and its nonphosphorylated counterpart (biot-Add). The major side-reactions were H₂S elimination on the cysteine residues and H₂O elimination on the non phosphorylated serine residue of biot-Add. The former dilutes the MALDI-TOF signal for the desired species. The latter gives a product similar to what is obtained by H₃PO₄ elimination and should prompt to caution when working with a mixture between phosphorylated and non phosphorylated peptides. Modifications on the solvent, the reaction temperature and time, the nature, and concentration of the base were made. Major improvement of the selectivity of the reaction was observed in 30?% ACN, at room temperature for 4?h. However, these optimizations are specific to these sequences and should be performed anew for different peptides. The selectivity of the reaction towards H₃PO₄ elimination is improved, but the persistence of side-reactions renders a previous sample fractionation necessary. In these optimized conditions, the ionization enhancement is 3-fold and the detection limits for biot-pAdd are similar to biot-Add (100?fmol).     

Synthesis of a Novel Perfluorinated Vinyl Ether Containing Sulfonimide and Phosphonic Acid Functionalities

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