Preparation and evaluation of a series of α‐hydroxy ethers from 9,10‐epoxystearates

Several novel α‐hydroxy ethers were prepared by treatment of isobutyl 9,10‐epoxystearate with a number of aliphatic alcohols in the presence of acid catalyst in good overall yield from oleic acid. The low‐temperature behavior of each material was analyzed through cloud point (CP) and pour point (PP) determination. The most desirable α‐hydroxy ether prepared in this study was isobutyl 9(10)‐(2‐ethylhexoxy)‐10(9)‐hydroxystearate. Therefore, additional α‐hydroxy‐2‐ethylhexyl ethers were produced from alkyl 9,10‐epoxystearates (alkyl: butyl, hexyl, 2‐methylpentyl, 2‐ethylbutyl, 2‐ethylhexyl) to explore the effect of ester variability on CP and PP of the optimized 2‐ethylhexyl ether moiety. The most bulky ester group, 2‐ethylhexyl, exhibited the most favorable low‐temperature performance, which in the case of 2‐ethylhexyl 9(10)‐(2‐ethylhexoxy)‐10(9)‐hydroxystearate yielded a CP of –26 °C and a PP of –29 °C. An improved synthesis of 2‐ethylhexyl 9(10)‐(2‐ethylhexoxy)‐10(9)‐hydroxystearate was then developed from oleic acid. Lastly, in an effort to optimize yield, sulfuric acid at 10 mol‐% was found to be the most effective acid catalyst in the conversion of epoxides to α‐hydroxy ethers.     

Study of Antioxidative Properties of Some Mono Amino‐Acid‐Type and Dipeptide‐Type Surfactants

Surfactants of tryptophan, tyrosine, and histidine were successfully synthesized. They were then modified to obtain dipeptide‐type surfactants with better solubility in both polar and nonpolar solvents, giving more emphasis to the development of water‐soluble amino‐acid‐type surfactants. All developed materials were designed to have functionality as antioxidants (AOX). The investigation of free radical scavenging capacity at pre‐micellar concentrations revealed greater Trolox equivalent (TE, relative scavenging capacity to Trolox) results for Trp‐type surfactants followed by Tyr‐type and His‐type. As expected, the synthesized surfactants exhibited comparable AOX properties to their parent amino acids. The AOX behavior of these surfactants was also checked in micellar concentrations, and the trend was found to be analogous: Trp‐type > Tyr‐type > His‐type surfactants. However, all of them were acting as better AOX in the micellar state than in the monomeric state. Investigating the synergistic effect found no interaction between the “amino acid–surfactant” pairs or the “surfactant–surfactant” pairs with varying ratios. They showed total AOX activity with respect to that of each material. This work opens up the door to the application of some new oil and water‐soluble amino‐acid‐type surfactants having auspicious AOX activity.     

Formation of 4‐Hydroxy‐2‐Trans‐Nonenal,a Toxic Aldehyde,in Thermally Treated Olive and Sunflower Oils

4‐Hydroxy‐2‐trans‐nonenal (HNE) is a toxic aldehyde produced mostly in oils containing polyunsaturated fatty acid due to heat‐induced lipid peroxidation. The present study examined the effects of the heating time, the degree of unsaturation, and the antioxidant potential on the formation of HNE in two light olive oils (LOO) and two sunflower oils (one high oleic and one regular) at frying temperature. HNE concentrations in these oil samples heated for 0, 1, 3, and 5 hours at 185 °C were measured using high‐performance liquid chromatography. The fatty‐acid distribution and the antioxidant capacity of these four oils were also analyzed. The results showed that all oils had very low HNE concentrations (<0.5 μg g^?1 oil) before heating. After 5 hours of heating at 185 °C, HNE concentrations were increased to 17.98, 25.00, 12.51, and 40.00 μg g^?1 in the two LOO, high‐oleic sunflower oil (HOSO), and regular sunflower oil (RSO), respectively. Extending the heating time increased HNE formation in all oils tested. It is related to their fatty‐acid distributions and antioxidant capacities. RSO, which contained high levels of linoleic acid (59.60%), a precursor for HNE, was more susceptible to degradation and HNE formation than HOSO and LOO, which contained only 6–8% linoleic acid.     

Undecanoic and 10-Undecenoic Acid-Based Amidobetaines and Amidoamine Oxides

Three types of undecanoic and 10-undecenoic acid-based surfactants were synthesized in the present work: amphoteric amidobetaines, cationic amidobetaine chlorides and nonionic amidoamine oxides. Structural characterizations of synthesized compounds were based on nuclear magnetic resonance (NMR) (¹H and ¹³C) and mass spectrometry. Surface properties, such as critical micelle concentration (CMC), surface tension at cmc (γ _cmc), efficiency of surface adsorption (pC20), surface excess (Γ_max) and minimum area per molecule (A _min) at the air–water interface, were determined by surface tension methods. Fluorescence probing techniques were also employed for the measurement of CMC, as well as steady state anisotropy (r) at the micellar core. The CMC of the studied surfactants follow the order: amidobetaine > amidobetaine chloride > amidoamine oxide. The influence of the terminal double bond in the hydrophobic alkyl chain on CMC was also assessed, and a significant increase in CMC was found due to the introduction of the double bond in the cases of amidobetaine chlorides and amidoamine oxides. These two types of surfactants showed higher rigidity at the micellar core compared to their corresponding unsaturated counterparts. However, such influence of unsaturation on the hydrophobic moiety was not observed in the case of amidobetaines. In all three types of surfactants, the saturated surfactant exhibited a lower γ _cmc and A _min, but higher Γ_max, r and pC20 compared to its unsaturated counterpart.     

Chemo‐enzymatic synthesis of lipophilic ferulates and their evaluation for antioxidant and antimicrobial activities

An efficient chemo‐enzymatic synthesis of ferulic acid‐based structured lipids mimicking triacylglycerol with a pendant phenolic moiety was carried out for the first time. Initially, ferulic acid was reduced to coniferyl alcohol, followed by its esterification with fatty acids. The key step in the synthesis was dihydroxylation of the olefinic side chain of coniferyl ester, which was eventually esterified with fatty acids to generate phenolic structured lipids. Two such compounds of varying fatty acid chain lengths were synthesized in good yield. Structural confirmation of both compounds is based on IR, ¹H and ¹³C NMR, and MS techniques. The synthesized compounds were tested for in vitro antioxidant and antimicrobial activities. Both compounds exhibited moderate to good antioxidant activity. The phenolic structured lipid with only shorter‐chain fatty acids showed antibacterial activity. Both compounds did not show any antifungal activity.     

1-C_(10)/1-C_(14)混合烯烃齐聚制备高性能润滑油基础油

1-C_(10)烯和1-C_(14)烯混合烯烃在AlCl_3催化剂作用下发生齐聚反应合成了高性能的聚α-烯烃基础油(PAO)。对齐聚产物进行了核磁共振氢谱表征,讨论1-C_(10)烯和1-C_(14)烯齐聚产物的分子结构。考察了反应温度(25℃、50℃)、原料不同混合比对齐聚产物性能(υ100℃、VI、凝点)的影响,产物粘度、凝点的测定均按照国家标准的石油和石油产品试验方法。结果表明:该混合物具有中等粘度(υ100℃=12.02~28.01 mm~2/s)、较高粘度指数(VI=123~175)、较低凝点(PP=-25~-58℃),可作为高性能润滑油基础油。     

Preparation,Crystal Structure and Explosive Properties of Copper(II) Perchlorate Complex with 4‐Amino‐1,2,4‐Triazole and Water

A complex from copper(II) perchlorate with 4‐amino‐1,2,4‐triazole (4‐AT, C₂H₄N₄) was synthesized, and elemental composition, molecular structure, and explosive properties were determined. To this end, elemental and X‐ray analyses were carried out, sensitivity to mechanical and thermal stimuli was measured, mechanism of thermal decomposition was investigated, and kinetic parameters of decomposition were determined. In the next step measurements of heat of combustion and detonation velocity were performed. Detonation parameters were also calculated. It was stated that the complex has slightly distorted square bipyramidal (4+2) coordination. The four basal bonds are formed by nitrogen atoms of four 4‐AT molecules. The coordination of the metal is completed by two axial oxygen atoms, one of the perchlorate ion, and one of the water molecule. With respect to explosive properties, tetrakis(4‐AT)copper(II) perchlorate monohydrate belongs to the group of sensitive secondary explosives.     

Kinetics of antioxidant action of α‐ and γ‐toco‐pherols in sunflower and soybean triacylglycerols

A kinetic analysis was performed to evaluate the antioxidant behavior of α‐ and γ‐to‐copherols (5—2000 ppm) in purified triacylglycerols obtained from sunflower oil (TGSO) and soybean oil (TGSBO) at 100 °C. Different kinetic parameters were determined, viz. the stabilization factor as a measure of effectiveness, the oxidation rate ratio as a measure of strength, and the antioxidant activity which combines the other two parameters. In the low concentration range (up to 400 ppm in TGSBO and up to 700 ppm in TGSO) α‐tocopherol was a more active antioxidant than γ‐tocopherol whereas the latter was more active at higher concentrations. It has been found that the different activity of the tocopherols is not due to their participation in chain initiation reactions, but that the loss of antioxidant activity at high tocopherol concentrations is due to their consumption in side reactions. The rates of these reactions are higher in TGSBO than in TGSO. Both α‐tocopherol itself and its radicals participated more readily in side reactions than γ‐tocopherol and its radicals. Both α‐ and γ‐tocopherol reduce lipid hydroperoxides, thus generating alkoxyl radicals which are able to amplify the rate of lipid oxidation by participating in chain propagation reactions.     

Electropreparation of (±)‐10‐camphorsulfonate‐doped poly(o‐phenylenediamine) in acetonitrile and its use in determination of glucose

Poly(o‐phenylenediamine) (PoPD) film has been electrochemically prepared on Pt electrode in an acetonitrile–water medium containing o‐phenylenediamine (oPD) monomer and (±)‐10‐camphorsulfonic acid (HCSA) by using the cyclic voltammetry (CV). The PoPD film (PoPD–CSA) has been characterized by FTIR, CV, EIS, FESEM, and conductivity measurement. The glucose biosensor (Pt/PoPD–CSA/GOx) has been prepared from the PoPD coated electrode by immobilizing glucose oxidase (GOx) enzyme using glutaraldehyde. The biosensor shows a low detection limit and wide linear working range, a good reusability, long‐term stability, and anti‐interference ability. The Pt/PoPD–CSA/GOx has possesses higher sensitivity (2.05 μA/mmol L^?1) and affinity to glucose due to the use of CSA ion as dopant. The linear concentration ranges of Pt/PoPD–CSA/GOx have been found to be 9.6 × 10^?3 to 8.2 mmol L^?1 from calibration curve and 4.6 × 10^?2 to 100 mmol L^?1 from the relationship between the (1/glucose concentration) and (1/current difference). © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39864.     

Surface Tensions of Carbonated 2‐Amino‐2‐methyl‐1‐propanol and Piperazine Aqueous Solutions

Surface tensions of carbonated 2‐amino‐2‐methyl‐1‐propanol (AMP) and piperazine (PZ) aqueous solutions were measured by a surface tension meter which employs the Wilhemy plate principle. A thermodynamic model was proposed to correlate the surface tensions of both CO₂‐unloaded and CO₂‐loaded aqueous solutions by introducing the contribution of CO₂ loading into the formulation of surface tension. Based on experiments and calculations, the effects of temperature, mass fractions of amines, and CO₂ loading on surface tensions of carbonated aqueous solutions were demonstrated.     

Synthesis of the Ammonium Salt of 6‐Amino‐2‐hydroxy‐ 3,5‐dinitropyrazine and a Comparison of its Properties with those of Ammonium 3,5‐Diaminopicrate (ADAP)

The ammonium salt of 6‐amino‐2‐hydroxy‐3,5‐dinitropyrazine has been synthesised from 2,6‐dimethoxy‐3,5‐dinitropyrazine and its properties (DSC, crystal structure, impact sensitiveness and thermochemical properties) are compared with the analogous benzene derivative, ammonium 3,5‐diaminopicrate.     

13‐Hydroxy‐9Z,11E‐Octadecadienoic Acid Production by Recombinant Cells Expressing Burkholderia thailandensis 13‐Lipoxygenase

Linoleate 13‐lipoxygenase from Burkholderia thailandensis was expressed in Escherichia coli for the production of 13‐hydroxyoctadecadienoic acid (13‐HODE), an antiseptic emulsifier. Linoleate 13‐lipoxygenase in cells had higher thermal stability than the purified enzyme. To increase 13‐HODE production, recombinant cells were permeabilized by solvents, detergents, salts, and other chemicals. The enzymatic activity in cells was the highest for permeabilized cells treated with 0.5 M NaCl among the permeabilizers tested. The optimal reaction conditions for the production of 13‐HODE from linoleic acid by permeabilized cells treated with 0.5 M NaCl were at pH 7.5, 25 °C, 20 g/l linoleic acid, 15 g/l cells, 0.15 mM Cu²⁺, and 6 % (v/v) methanol in a 100‐ml baffled flask containing a 5‐ml working volume with agitation at 200 rpm. Under these conditions, permeabilized cells produced 15.8 g/l 13‐HODE after 30 min with a conversion yield of 79 % (w/w) and a productivity of 31.6 g/l/h. The conversion yield and productivity of permeabilized cells for 13‐HODE production were higher than those of purified and crude enzymes as well as nonpermeabilized cells. Therefore, permeabilized cells were efficient biocatalysts for 13‐HODE production. To the best of our knowledge, this is the first report of the production of 13‐HODE using cells.     

Phenolic antioxidants – radical‐scavenging and chain‐breaking activity: A comparative study

Fifty phenolic antioxidants (AH) (42 individual compounds and 8 binary mixtures of two antioxidants) were chosen for a comparative analysis of their radical‐scavenging (H‐donating) and chain‐breaking (antioxidant) activity. Correlations between experimental (antiradical and antioxidant) and predictable (theoretical) activities of 15 flavonoids, 15 hydroxy cinnamic acid derivatives, 5 hydroxy chalcones, 4 dihydroxy coumarins and 3 standard antioxidants (butylated hydroxytoluene, hydroquinone, DL ‐α‐tocopherol) were summarized and discussed. The following models were applied to explain the structure‐activity relationships of phenolic antioxidants of natural origin: (a) model 1, a DPPH assay used for the determination of the radical‐scavenging capacity (AH + DPPH? → A? + DPPH‐H); (b) model 2, chemiluminescence of a model substrate RH (cumene or diphenylmethane) used for the determination of the rate constant of a reaction with model peroxyl radicals (AH + RO₂? → ROOH + A?); (c) model 3, lipid autoxidation used for the determination of the chain‐breaking antioxidant efficiency and reactivity (AH + LO₂? → LOOH + A?; A? + LH (+O₂) → AH + LO₂?); and (d) model 4, theoretical methods used for predicting the activity (predictable activity). The highest lipid oxidation stability was found for antioxidants with a catecholic structure and for their binary mixtures with DL ‐α‐tocopherol, as a result of synergism between them.     

Crystallization and melting behavior of blends comprising poly(3‐hydroxy butyrate‐co‐3‐hydroxy valerate) and poly(ethylene oxide)

Blends of poly(3‐hydroxy butyrate‐co‐3‐hydroxy valerate) (PHBV) and poly(ethylene oxide) (PEO) were prepared by casting from chloroform solutions. Crystallization kinetics and melting behavior of blends have been studied by differential scanning calorimetry and optical polarizing microscopy. Experimental results reveal that the constituents are miscible in the amorphous state. They form separated crystal structures in the solid state. Crystallization behavior of the blends was studied under isothermal and nonisothermal conditions. Owing to the large difference in melting temperatures, the constituents crystallize consecutively in blends; however, the process is affected by the respective second component. PHBV crystallizes from the amorphous mixture of the constituents, at temperatures where the PEO remains in the molten state. PEO, on the other hand, is surrounded during its crystallization process by crystalline PHBV regions. The degree of crystallinity in the blends stays constant for PHBV and decreases slightly for PEO, with ascending PHBV content. The rate of crystallization of PHBV decreases in blends as compared to the neat polymer. The opposite behavior is observed for PEO. Nonisothermal crystallization is discussed in terms of a quasi‐isothermal approach. Qualitatively, the results show the same tendencies as under isothermal conditions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2776–2783, 2006