Quantitative determination of carboxylate by infrared spectroscopy: application to humic acids

The carboxylate content has been determined by infrared (IR) spectroscopy in different commercial salts of carboxylic acids and also in commercial and isolated samples of soil humic acids. A linear standard curve using anhydrous sodium salicylate has been obtained from the plot of carboxylate (COO^–) concentration vs. the weight of the IR band area, using the COO^– antisymmetric stretch vibration at 1580 cm^–1. Parallel determinations of carboxy groups by the commonly used Ca(OAc)₂ method with related carboxylic acids and humic acids in the H⁺ form has been carried out for comparison. A much better sensitivity and a similar accuracy was obtained. This method is furthermore much faster, simpler and more economical, and offers in some cases a better applicability.     

Oxidation of brown coal of Angren deposit with a mixture of nitric and sulfuric acids

Oxidation of brown coal of Angren deposits by a mixture of nitric and sulfuric acids was studied in respect of dependence on the concentration of nitric acid (5–30%), concentration of sulfuric acid in nitric acid solution (2.5–20%), and temperature (40–80°C) at the process duration 2 h and the ratio of coal: HNO₃ = 1: 2. Optimal conditions of the process in terms of maximum yield of humic acids and the minimum loss of nitrogen oxides were found.     

An X-ray diffraction study of alkylammonium humate complexes

By exchange of cations of different humates (synthetic, brown coal and compost humates) with an equivalent amount of long-chain organic cations, derivatives with the following alkylammonium ions were prepared: n-decyl, n-dodecyl, n-tetradecyl, n-hexadecyl and n-octadecyl ammonium ions. X-ray diffraction of the humic acids and the alkylammonium humates revealed a behaviour similar to that of smectite-type clay minerals. The results seem to support the layer structure of humic substances. The layers of synthetic, brown coal and compost humate are about 0.60, 0.45 and 0.84 nm thick, and the bilayers of alkylammonium cations are bound to the carboxyl and phenolic hydroxyl groups. The chain tilt is 41–45 .     

内蒙胜利褐煤腐殖酸对煤平衡复吸水的影响

研究了褐煤中重要的成分腐殖酸对褐煤水分的影响。测定了内蒙胜利褐煤中腐殖酸含氧官能团的含量,并分析了褐煤、棕黑腐殖酸和残余煤的等温吸附和脱附曲线。通过Dent吸附等温模型研究了褐煤和棕黑腐殖酸第一层吸附和第二层吸附。结果表明,胜利褐煤2/5羧基和1/5羟基是由腐殖酸提供的。棕黑腐殖酸相对褐煤孔径和孔容较小,不利于水簇的形成。腐殖酸对褐煤的复吸水是不利的     

Adsorption interactions of humic acids with biocides

The chemical composition of humic acids from brown coal (Aldrich) was determined by element analysis, ¹³C NMR spectroscopy, and potentiometric titration. The adsorption ability of humic acids with different biocides (cyproconasol, propiconasol, tebuconasol, irgarol 1051, and DCOIT) was studied. The adsorption ability of a mixture of biocides in aqueous solutions was higher than that of the individual components. The limiting concentration of humic acids at which adsorption of biocides was maximum was determined. Adsorption constants were calculated by the Freundlich equation for each biocide in aqueous solution.     

经济实用的Boc保护氨基酸键合氯甲基树脂的方法研究

在固相多肽合成中, 探索一种经济有效的Boc保护氨基酸键合氯甲基树脂的方法. 采用K₂CO₃/KI作为键合试剂, 一步合成产物, 反应条件为: Boc保护氨基酸2.5倍量, K₂CO₃ 2.5倍量, KI 0.01倍量, 氯甲基树脂1.0倍量, 普通DMF作反应溶剂, 70 ℃空气浴中旋转反应25 h. 考察了28种不同结构的氨基酸底物在此条件下与氯甲基树脂的键合收率, 大多数氨基酸都能得到几乎定量的酯化产率. 并选取了不同空间位阻的4种Boc保护氨基酸, 比较了KOH, Cs₂CO₃, TEA/KI, DCHA/KI, DIPA/KI, Cs₂CO₃/KI和K₂CO₃/KI等不同键合条件对收率的影响. 结果表明, 除Boc-Asn-OH外, K₂CO₃/KI条件与Cs₂CO₃/KI的效果大体相同, 但K₂CO₃/KI更为经济、可行.     

Complexation of Eu3+ and Am3+ with soil humic acid extracted from Okchon Basin of Korean Peninsula

The complexation of Eu³⁺ and Am³⁺ ions with the humic acids has been investigated at various pH (4.0, 4.5, 5.0, 5.4) in 0.1M NaClO₄ solution using solvent extraction technique. Two humic acids are used in this study: humic acid extracted from the soil of Taejon on the Okchon Basin of Korea (TJHA) and commercially available one from Aldrich Chemical Co. (AHA). The total carboxylate group concentrations were determined to be 3.58 meq/g and 4.59 meq/g for Taejon and Aldrich humic acids, respectively. The conditional stability constants (log ₁ and log ₂), dependent on the pH of the solution, of the complexes of Eu³⁺ and Am³⁺ ions with the humic acids have been determined at the ionic medium of 0.1M NaClO₄. The values of stability constants with the degree of ionization of TJHA for Eu and Am complexes are quite well agreed with those of Lake Bradford humic acid (LBHA), indicating that structural characteristics of TJHA and LBHA may be quite similar to one another.     

Synthesis, structure, and antimicrobial activity of copper(II) chelates containing imidazole and condensation products of α-amino acids with salicylaldehyde and its derivatives

Salicylaldehyde, 5-bromo- and 5-nitrosalicylaldehydes, 2-hydroxynaphthalene-1-carbaldehyde, and 2,3-, 2,4-, and 2,5-dihydroxybenzaldehydes reacted with glycine, alanine, and phenylalanine in ethanol in the presence of imidazole (Im) and copper(II) acetate hydrate to give copper(II) chelates with the composition Cu(Im)(L) · nH₂O (H₂L is the condensation product of the above aldehydes with α-amino acids; n = 0–2). The structure of the complex Cu(Im)(L¹) [H₂L¹ = 2-(2-hydroxybenzylideneamino)acetic acid] was determined by X-ray analysis. The crystalline structure of [2-(2-hydroxybenzylideneamino)acetato](imidazole)copper is formed by polymeric chains of the Cu(Im)(L¹) molecules linked through bridging oxygen atoms in the carboxy groups of the Schiff base ligand. The coordination unit has a distorted tetragonal pyramid configuration, where the pyramid base is composed of the phenol and carboxy oxygen atoms, CH=N nitrogen atom in the ligand H₂L¹ and imidazole nitrogen atom. The oxygen atom in the carboxy group in the neighboring molecule occupies the apical position of the coordination pyramid. The other coordination compounds also have polynuclear structure with the Schiff base H₂L acting as doubly deprotonated tridentate O,N,O-ligand and bridging carboxy groups. Thermal decomposition of the complexes includes their dehydration (70–95°C), while complete thermal decomposition occurs at 360–530°C. The synthesized complexes showed selective antimicrobial activity in the concentration range from 75 to 300 μg/ml against a number of standard strains of Staphylococcus aureus and Escherichia coli.     

13C NMR spectra of a number of penta- and hexacyclic triterpenoids derived from glycyrrhetic acid

The¹³C NMR spectra of 22 derivatives of 18α- and 18β-glycyrrhetic acids that have been investigated and an assignment of the signals has been made. It has been shown that a modification of the carboxy group of glycyrrhetic acid leads mainly to a change in the chemical shifts of the α-, β-, and γ-carbon atoms of ring E. The assignment of a number of signals has been confirmed by the use of the shift reagent Eu(fod)_s. It has been established that the C₂₈ and C₁₆ signals are the most sensitive to a change in the C₁₈ configuration in the spectra of glycyrrhetic acid derivatives.

     

The additivity principle in pyrolysis—gas chromatography of brown coal

Pyrolysis—gas chromatography of brown coal exhibits additive properties and it is therefore possible to construct the pyrogram of the original coal from the individual pyrograms of the bitumen, humic acids, lignin and humin fractions. The contents of phenols in the pyrograms are typical for all of the above classes except bitumen and are in agreement with the contents of the individual groups in the original coal. The results suggest that the separation does not bring about significant chemical changes in individual brown coal fractions.     

Fe对胜利褐煤焦结构和气化反应性能的影响

酸洗褐煤负载不同含量的Fe催化剂在固定床反应器上进行热解,然后采用FT-IR、Raman spectra、TPD和TG研究Fe催化剂对煤焦官能团、碳微晶结构、表面活性位和气化反应性的影响。FT-IR结果表明,催化热解作用下煤焦中-OH、-CH₃、-CH₂活性官能团数量增加。Raman光谱测试结果显示,随着Fe含量的增加,I_G/I_all由0.095减少到0.087,I_D3/I_all由0.090增加至0.097,表明在Fe催化作用下部分大芳香环结构转变为小芳香环结构。TPD实验结果表明,活性位数量随着煤焦中Fe含量升高而不断增加。在3%含Fe量时煤焦活性位数量随着吸附温度的升高而增加,800 ℃后煤焦表面活性位数量开始降低。750 ℃条件下CO₂吸附量随着吸附时间的延长而增加,45 min后煤焦达到饱和吸附状态。煤焦-水蒸气等温气化实验表明,煤焦气化反应性与活性位数量有密切的关系,Fe催化剂主要通过增加煤焦表面活性位数量提高煤焦气化反应性。     

Tertiary-Amine-Initiated Synthesis of Acyl Fluorides from Carboxylic Acids and CF3SO2OCF3

A convenient method for deoxyfluorination of aromatic and aliphatic carboxylic acids with CF₃SO₂OCF₃ in the presence of a suitable base at room temperature has been developed. The reaction allows a straightforward access to a variety of acyl fluorides and proves that CF₃SO₂OCF₃ is an effective deoxyfluorination reagent for carboxylic acids. The method features simplicity, expeditiousness, high efficiency, ease of handling, good functional group tolerance, a wide range of substrates, excellent yields of products, compatibility of many amine initiators, use of environmentally friendly reagents, and effortless removal of byproducts. This reaction represents the first utilization of trifluoromethyl trifluoromethanesulfonate as a fluorination reagent.     

Comparative characteristic studies on soil and commercial humic acids

Summary Two commercial and eight soil humic acids were characterized to evaluate the use of commercial humic materials in soil and environmental studies. Significant differences between commercial and soil humic acids were observed in ash content, major and micro-element constituents, E₄/E₆ ratio, total acidity and ¹³C-NMR spectroscopy; but data from stability constant and IR-spectroscopy were almost identical. The commercial materials appeared to be significantly less aromatic and more aliphatic in nature as compared with representative soil humic acids. The above discrepancies were interpreted as indicating an origin of the respective commercial product other than soil. The two commercial humic acids investigated may not originate from the same source material as evidenced by clear-cut differences in the intensity of the ¹³C-NMR spectra in almost all chemical shift regions. Due to the observed structural, compositional and characteristic dissimilarities, both between soil and commercial humic acids and between different commercial ones, the commercial humic products are not recommended to be used as analogues of real soil humic acids in soil and environmental studies.     

A Novel Reagent for Radioiodine Labeling of New Chemical Entities (NCEs) and Biomolecules

Radioiodine labeling of peptides and proteins is routinely performed by using various oxidizing agents such as Chloramine T, Iodobeads, and Iodogen reagent and radioactive iodide (I⁻), although some other oxidizing agents were also investigated. The main objective of the present study was to develop and test a novel reagent, inorganic monochloramine (NH₂Cl), for radioiodine labeling of new chemical entities and biomolecules which is cost-effective, easy to make and handle, and is selective to label amino acids, peptides, and proteins. The data presented in this report demonstrate that the yields of the non-radioactive iodine labeling reactions using monochloramine are >70% for an amino acid (tyrosine) and a cyclic peptide (cyclo Arg-Gly-Asp-d-Tyr-Lys, cRGDyK). No evidence of the formation of N-chloro derivatives in cRGDyK was observed, suggesting that the reagent is selective in iodinating the tyrosine residue in the biomolecules. The method was successfully translated into radioiodine labeling of amino acid, a peptide, and a protein, Bovine Serum Albumin (BSA).     

Effect of HF Modification on the Catalytic Properties of Ferrospheres in the Oxidative Coupling of Methane

The effect of the HF modification of ferrospheres separated from fly ash after the combustion of brown coal on their chemical, phase compositions and catalytic properties in the oxidative coupling of methane was studied. The modification led to a change in the phase composition in comparison with that of the initial ferrospheres: a CaF₂ phase appeared, the hematite phase content increased, and the ferrospinel content decreased. The yield of C₂ hydrocarbons at 750°C increased by a factor of 1.5–2.0, and the fraction of ethylene in them increased to 30 or 65% at 750 or 850°C, respectively. It was assumed that an increase in the efficiency of HF-modified ferrospheres in the formation of ethane and its dehydrogenation into ethylene was due to the formation of oxyfluoride-type active sites. The pyrohydrolysis of fluorine-containing catalyst components at 850°C due to interaction with water vapor in a reaction atmosphere led to the formation of systems active in deep oxidation; this manifested itself in a sharp decrease in selectivity for the formation of C₂ hydrocarbons and an increase in selectivity for CO₂.

     

Facile and effective approach for oxidation of boronic acids

This present work illustrates facile and effective approach for oxidation of boronic acids using environmentally benign dimethyl carbonate (DMC) as a solvent with H₂O₂ as an oxidant at room temperature. In contrast to previous reaction reports, which make use of metal catalyst, hazardous reagent and oxidants that creates environmental concern. This method provides good to excellent yield of products and showed better tolerance towards various functional groups present on boronic acids. Moreover, this developed process is an alternative in terms of inexpensive, non toxic and easy reaction conditions.     

Capillary zone electrophoresis to study the humic fraction in organic soils and its relationship with radiocaesium mobility

Humic acids and associated radionuclides were extracted from several soil samples with a significant organic matter content, such as peaty soils and forest soil layers. Extractions were made using two alkaline solutions (Na₄P₂O₇ 0.1 mol·1^–1 and NaOH 0.1 mol·1^–1 under N₂). The humic acid content in the extract was determined by the capillary zone electrophoresis technique (CZE) and associated radiocaseium was determined by gamma spectrometry. After analizing a large number of samples and studying the relationship between humic acid and organic matter content it was possible to conclude that the CZE technique may be a good alternative to classical techniques in humic acid determinations, with NaOH extractions leading to higher results than Na₄P₂O₇. Furthermore, the quantification of the radiocaseium desorbed by applying different extractant reagents (NaOH, Na₄P₂O₇, NH₄AcO and CaCl₂) showed that there may be some organic matter-radionuclide interations, other than those originated by humic acids. which may govern radionuclide retention in soils with a high content of organic matter.     

Active sites of the functionalized coals and carbons for oxygen reduction reaction in a fuel cell

The active sites of the coals and carbons functionalized with added nitrogen, oxygen and iron were studied for the oxygen reduction reaction (ORR) in a fuel cell. The catalysts were characterized based on the XPS, Raman, TEM, XRD and N₂ adsorption measurements. The ORR activity was promoted by the addition of iron and aluminum as the inorganic components of the ash to the ash-free brown coal. The ORR activity of the ash-components added to the ash-free brown coal was correlated to the I _D/I _G ratio (deficient carbon degree) and the pyridinic nitrogen based on the Raman and XPS analyses, respectively. The active sites of the brown coal were formed at the pyridinic nitrogen on parts of the defective carbons associated with iron on the alumina. On the other hand, for the nitrogen-doped carbons without iron, the ORR activity was related to the pyrrolic-NH, pyridinic nitrogen species and the defective carbon degree. Based on these results, the active sites of the iron-added and nitrogen-doped coals and carbons were the iron sites coordinated with the pyridinic nitrogen, while the active sites of the iron-free and nitrogen-doped carbons without iron were the pyrrolic-NH and pyridinic-NH⁺ sites of parts of the defective carbons. The difference between the active sites of the nitrogen-doped coals and carbons in the presence of iron and those in the absence of iron was discussed. These results suggested that the pyridinic N as a base site transformed into pyridinic-NH⁺ as an acid site by attack of the proton from the anode.     

A Safe,Simple and Rapid Synthesis of t-Butyl Chromate

Di-t-butyl chromate -(t-BuO)₂CrO₂, DTBC- has proven to be a potent and versatile oxidizing reagent, suitable for the direct introduction of a carbonyl group in an allylic position¹. The compound was prepared for the first time by Wienhaus² but Oppenauer³ introduced it as a new oxidizing reagent. DTBC is a crystalline compound with a melting point of 0°C^3,4 and is never used as such but always in a solution of a non polar solvent.     

Structure Selectivity of Alkaline Periodate Oxidation on Lignocellulose for Facile Isolation of Cellulose Nanocrystals

Reported here for the first time is the alkaline periodate oxidation of lignocelluloses for the selective isolation of cellulose nanocrystals (CNCs). With the high concentrations as a potassium salt at pH 10, periodate ions predominantly exist as dimeric orthoperiodate ions (H₂I₂O₁₀^4?). With reduced oxidizing activity in alkaline solutions, dimeric orthoperiodate ions preferentially oxidized non‐ordered cellulose regions. The alkaline surroundings promoted the degradation of these oxidized cellulose chains by β‐alkoxy fragmentation and generated CNCs. The obtained CNCs were uniform in size and generally contained carboxy groups. Furthermore, the reaction solution could be reused after regeneration of the periodate with ozone gas. This method allows direct production of CNCs from diverse sources, in particular lignocellulosic raw materials including sawdust (European beech and Scots pine), flax, and kenaf, in addition to microcrystalline cellulose and pulp.