The Influence of Tocopherols on the Oxidation Stability of Methyl Esters

Tocopherols were found to be the principal natural antioxidants in biodiesel grade fatty acid methyl esters. The stabilising effect of α-, γ- and δ- tocopherols from 250 to 2,000 mg/kg was evaluated by thermal and accelerated storage induction times based on rapid viscosity increase, in sunflower (SME), recycled vegetable oil (RVOME), rapeseed (RME) and tallow (TME) methyl esters. Both induction times showed that stabilising effect is of the order of δ- > γ- > α-tocopherol, and that the stabilising effect increased with concentration. The correlation between the two induction times however was poor, which is probably due to the fact that the time they correspond to two different stages of oxidation. Tocopherols were found to stabilise methyl esters by reducing the rate of peroxide formation while present. The deactivation rates of tocopherols increased with unsaturation of the particular methyl ester and in the present work they were of the order of SME > RME > RVOME > TME. While α-tocopherol was found to be a relatively weak antioxidants, both γ- and δ- tocopherols increased induction times significantly and should be added to methyl esters without natural antioxidants.     

Graft copolymerization of vinyl monomers onto modified cottons. VIII. Dimethylaniline–benzyl chloride-induced grafting of methyl methacrylate onto partially carboxymethylated cotton

The feasibility of dimethylaniline (DMA)–benzyl chloride (BC) mixture to initiate graft polymerization of methyl methacrylate (MMA) onto partially carboxymethylated cotton was examined. The graft yield depends on the nature of the solvent used along with water; ethanol proved to be the best at a water;ethanol ratio of 90:10. Considerable grafting occurred in the presence of acetic acid at a concentration of 200 mmol/l. Higher concentrations of this acid decrease grafting significantly. The graft yield obtained in the presence of formic acid was much lower than that obtained in the presence of acetic acid. Inclusion of hydrochloric or sulfuric acid in the graft polymerization system prevent grafting. A DMA–BC mixture at a concentration of 0.08:0.087 mole/l. constitutes the optimal concentration for grafting. This contrasts with 0.32:0.35 mole/l. for total conversion. The rate of grafting increases by raising the polymerization temperature; it follows the order 50°>60°>65°>70°>75°C. Furthermore, increasing the monomer concentration caused a significant enhancement in the graft yield and total conversion.     

Redox-initiated vinyl graft copolymerization onto wool with thiourea as the reductant. III. Di-tert.-butyl peroxide thiourea system

Graft copolymerization of wool with methyl methacrylate (MMA) induced by di-tert.-butyl peroxide (DTBP)/thiourea (TU) system in acid medium was studied. The rate of the copolymerization reaction depends on concentrations of DTBP, TU and MMA, temperature as well as kind of acid and solvent used. The graft yield increases by increasing the concentration of DTBP and MMA. Increasing the temperature enhances also the graft formation; 60°C produces higher grafting than 50°C. Carrying out the graft polymerization reaction in acid medium by using nitric acid has proved to be the best in comparison with sulphuric and formic acid. There is an optimal concentration of TU (0.4 M); lower grafting is achieved below and above this concentration. A mixture of isopropanol/water at a ratio of 10:90 constitutes the most favourable reaction medium since increasing the solvent content is accompanied by a reduction in the graft yield. The kind of solvent does affect the graft yield: for the solvent studied, the graft yield follows the order: isopropanol < acetone < dimethylsulphoxide. Incorporation of an acid dye in the polymerization system to affect concurrent dyeing and grafting was carried out and the properties of the products so obtained were examined. The changes in alkali solubility of wool by grafting was also investigated. In addition, a reaction mechanism based essentially on complexes formed between DTBP and wool and/or DTBP and TU and their subsequent dissociation to give wool macroradicals was suggested.     

Nonvolatile α-branched chain fatty acid derivatives: III. Addition of acid chlorides,anhydrides and amides to terminal olefins

At-butyl peroxide initiated free radical reaction was employed for the preparation of α-branched fatty acid chlorides, which were then converted in situ to methyl esters. Similarly prepared were an α-branched fatty acid amide and an α-branched acid anhydride. The latter was converted to the methyl ester. The use of the acid chloride and acid anhydride permitted reduction in the molar ratio of reactants to half or less than that used in the addition of esters to terminal olefins without affecting the yield. The resulting increase of α-branched product concentration in the reaction mixture also made isolation of the product easier. The direct addition of a variety of stearic acid derivatives to 1-decene under the same conditions (20:4:1.2 molar ratio of reactants at 160 C) gave the following olefin based yield order: stearoyl chloride > stearic anhydride > stearamide and methyl stearate > stearic acid. Presented at the AOCS Meeting, Chicago, October 1967. E. Utiliz. Res. Dev. Div., ARS, USDA.     

Long chain fatty acid methyl ester hydrolase activity in mammalian cells

Long chain fatty acid methyl esters were hydrolyzed by cell free homogenates and subcellular fractions prepared from Ehrlich ascites tumor cells. The highest enzyme specific activity was observed in the microsomal fraction. Maximum hydrolase activity occurred in the pH range of 6.5–7.0. The relative activities for the methyl ester substrates that we tested were: methyl palmitate > methyl laurate > methyl oleate > methyl stea-rate. Butyl palmitate also was hydrolyzed by this enzyme. Enzymatic activity increased when the methyl ester-albumin complex concentration or the methyl ester-albumin molar ratio was raised. In addition to Ehrlich cells, methyl ester hydrolase activity was observed in homogenates of rat heart and liver. The highest enzyme specific activities also occurred in the microsomal fractions prepared from these tissues. Research Career Development Awardee of the National Heart and Lung Institute (K4-HE-20,338).     

Substrate preferences for lipase-mediated acyl-exchange reactions with butteroil are concentration-dependent

Substrate preferences for pancreatic lipase-mediated acyl-exchange reactions with butteroil were concentration-dependent for the series of acyl donors and alcohol acceptors evaluated. For acidolysis reactions, the initial reaction rates and percent reaction yields after 18 h at 50 μmol acyl donor per gram substrate mixture were similar forn-fatty acids and their methyl and glycerol esters. At 400–500 μmol g⁻¹ (and greater), order of initial reaction rates and percent reaction yield was fatty acid glycerol esters > fatty acid methyl esters > fatty acids. At concentrations above 300–500 μmol g⁻¹, reaction inhibition was observed for fatty acid substrates, and inhibition took place at lower concentrations for the shorter-chainlength fatty acids of those evaluated (5–17 carbons). Inhibition was primarily attributed to acidification of the microaqueous environment of the lipase. Desorption of water by the fatty acid substrate may be a secondary mode of inhibition. The concentration dependence of initial reaction rates and percent reaction yield was similar for then-alcohol substrates evaluated (2–15 carbons) for alcoholysis reactions with butteroil. Optimum alcohol concentration was 375–500 μmol g⁻¹ (except for butanol, which was 1 mmol g⁻¹, above which reaction inhibition was observed. Inhibition was attributed to desorption of water from the enzyme by the alcohol substrate. Relative reactivity of classes of alcohols for this reaction system was primary alcohols > secondary alcohols > tertiary alcohols. Generally, alcoholysis reactions were faster than acidolysis reactions, and triacylglycerols were the best substrates for acidolysis reactions with butteroil at high levels (up to 2 mmol g⁻¹) of acyl donor substrate.     

Pentavalent vanadium ion-induced grafting of methyl methacrylate onto cotton cellulose

Graft polymerization of methyl methacrylate (MMA) onto cotton cellulose using vanadium pentanitrate as initiator was studied under a variety of conditions. The graft yield increased with increasing initiator concentration up to 8 mmole/l. and then decreased upon further increase in initiator concentration. Increasing MMA concentration from 1 to 5% was accompanied by a significant increase in the degree of grafting. The latter was also affected by the kind and concentration of the acid incorporated in the polymerization medium. Based on graft yields, the efficiency of the acids follows the order H₂SO₄ > HNO₃ > HClO₄. Replacement of the acid with isopropyl alcohol was also examined. An isopropyl alcohol concentration of 10% constitutes the optimal concentration for grafting. Maximum graft yield depends upon the polymerization temperature; it follows the order 50°C ≥ 60°C > 40°C > 30°C > 70°C. Reaction mechanisms for grafting in the presence of acid as well as in the presence of isopropyl alcohol are proposed.     

Peroxydiphosphate–metal ion–cellulose thiocarbonate redox system‐induced graft copolymerization of vinyl monomers onto cotton fabric

The grafting of methacrylic acid (MAA) and other vinyl monomers onto cotton cellulose in fabric form was investigated in an aqueous medium with a potassium peroxydiphosphate–metal ion–cellulose thiocarbonate redox initiation system. The graft copolymerization reaction was influenced by peroxydiphosphate (PP) concentration, the pH of the reaction medium, monomer concentration, the duration and temperature of polymerization, the nature of vinyl monomers, and the nature and concentration of metallic ions (activators). On the basis of a detailed investigation of these factors, the optimal conditions for the grafting of MAA onto cotton fabric with the said redox system were as follows: [Fe²⁺] = 0.1 mmol/L, [PP] = 2 mmol/L, [MAA] = 4%, pH‐2, grafting time = 2 h, grafting temperature = 70°C, and material/liquor ratio = 1 : 50. Under these optimal conditions, the graft yields of different monomers were in the following sequence: MAA ? acrylonitrile > acrylic acid > methyl acrylate > methyl methacrylate. The unmodified cellulosic fabric (the control) had no ability to be grafted with MAA with the PP–Fe²⁺ redox system. The percentage of grafting onto the thiocarbonated cellulosic fabric was more greatly enhanced in the presence of iron salts than in their absence. This held true when the lowest concentrations of these salts were used separately. A suitable mechanism for the grafting processes is suggested, in accordance with the experimental results. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1879–1889, 2003     

Influence of the chemical structure of dithiocarbamates with different R groups on the reversible addition‐fragmentation chain transfer polymerization

Four dithiocarbamates, carbazole‐9‐carbodithioic acid benzyl ester (R1), carbazole‐9‐carbodithioic acid naphthalen‐1‐ylmethyl ester (R2), 2‐(carbazole‐9‐carbothioylsulfanyl)‐2‐methyl‐propionic acid ethyl ester (R3), and (carbazole‐9‐carbothioylsulfanyl)‐phenyl‐acetic acid methyl ester (R4), were synthesized and used to the reversible addition‐fragmentation chain transfer (RAFT) polymerizations of styrene (St), methyl methacrylate (MMA), and methyl acrylate (MA), respectively. The influence of chemical structure of dithiocarbamates with different R groups on the RAFT polymerizations was investigated. The results showed that the four RAFT agents were effective RAFT agents for the polymerizations of styrene or MA, and that the polymerizations were well‐controlled with the characteristics of controlled/“living” polymerization. The polymerization rate of styrene with thermal initiation was markedly influenced by the chemical structures of the group R in dithiocarbamates, and decreased in the order of R3 > R2 > R4 > R1. For the polymerization of MA, the efficiency of RAFT agents was in the following order: R2–R3 > R1 > R4. However, they were not efficient enough to control the polymerization of MMA. The obtained polystyrene (PSt) with carbazole group labeled strongly absorbed UV light at 294 nm and emitted fluorescent light in N,N‐dimethyl formamide (DMF). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 982–988, 2007     

Pentavalent vanadium ion–cellulose thiocarbonate redox-system induced grafting of methyl methacrylate and other vinyl monomers onto cotton fabric

Cellulose thiocarbonate was prepared by reacting cotton cellulose fabric with carbon disulphide in the presence of sodium hydroxide. The treated fabric formed, with pentavalent vanadium ion, an effective redox system capable of initiating grafting of methyl methacrylate (MMA) and other monomers no+o the cotton fabric. The dependence of grafting on vanadium concentration, pH of the polymerization medium, temperature and duration of grafting, nature and concentration of monomer, and solvent/water ratio was studied. The results indicated that increasing the pentavalent vanadium (V^v) concentration up to 60 mmol/L was accompanied by enhancement in the rate of grafting; the latter was not affected by further increase in V^v concentration. Maximum grafting yield was achieved at pH 2; grafting fell greatly at higher pH. The rate of grafting followed the order: 70° > 60° > 50°C. The graft yield increased significantly by increasing the MMA concentration from 0.5 to 5%. Of the solvents studied, n-propanol and isopropanol enhanced the grafting rate provided that a solvent/water ratio of 5 : 95 was used; a higher solvent ratio decreased the magnitude of grafting. Other solvents, namely, methanol, ethanol, n-butanol, and acetone, in any proportion, decreased the rate of grafting. With the monomer used, the graft yield followed the order: methyl methacrylate > methyl acrylate > methacrylic acid > ethyl methacrylate > acrylic acid. Also reported was a tentative mechanism for vinyl-graft copolymerization onto cotton fabric using cellulose thiocarbonate-V^v. © 1993 John Wiley & Sons, Inc.     

Solution properties of polyacrylic esters. I. Light scattering and viscosity measurements in tetrahydrofuran

Dilute THF-solutions of different fractions of polymers of methyl, ethyl, n-propyl, n-, i- and t-butyl, n-hexyl, 2-ethylhexyl, and lauryl acrylate, prepared by solution polymerization in benzene, were studied by light scattering and viscosity methods. Poly(acrylic acid) was examined in dioxane. For the different polyacrylic esters the [η]-M_w-relations were established and the dependence of the radius of gyration <r²_w> on the molecular weight was determined.     

Liquid–Liquid Equilibrium for Systems Containing Epoxidized Oils,Formic Acid,and Water: Experimental and Modeling

Epoxidized oils are eco-friendly plasticizers, which are industrially produced through the epoxidation reaction in a formic acid-hydrogen peroxide autocatalyzed system. The fundamental knowledge to describe the phase equilibrium of systems after epoxidation reaction is lacking, which is crucial for the design of the purification facilities. This work reported experimental data for the liquid–liquid equilibrium of three systems, i.e., epoxidized fatty acid methyl esters + formic acid + water, epoxidized fatty acid 2-ethylhexyl esters + formic acid + water, and epoxidized soybean oil + formic acid + water, in the temperature range (303.15–348.15) K under atmospheric pressure. The results indicated that the liquid–liquid equilibrium constant of formic acid in the systems followed the order of epoxidized fatty acid 2-ethylhexyl esters > epoxidized fatty acid methyl esters > epoxidized soybean oil. Moreover, the obtained experimental data were correlated using nonrandom two liquid (NRTL) and universal quasi chemical (UNIQUAC) models. The maximum root mean square deviation (RMSD) values as low as 0.0052 and 0.0263 were estimated using the NRTL and UNIQUAC model, respectively. The NRTL model is more suitable than the UNIQUAC model to describe the liquid–liquid equilibrium behavior of these ternary systems.     

Graft copolymerization of methyl methacrylate and other vinyl monomers onto cotton fabric using ferrous cellulose thiocarbonate–N-bromosuccinimide redox initiation system

The cellulose thiocarbonate, in the fabric from, was treated first with a freshly prepared ferrous ammonium sulphate (FAS) solution. The sotreated fabric formed, with N-bromosuccinimide (NBS), an effective redox system capable of initiating grafting of methyl methacrylate (MMA) and other vinyl monomers onto the cotton fabric. The effect of the polymerization conditions the polymer criteria, namely, graft yeild, homopolymer, total conversion, and grafting efficiency, was studied. These polymer criteria were found to depend extensively upon concentrations of the Fe²⁺ ion (activator), NBS (initiator), and MMA; pH of the polymerization medium, and duration and temperature of polymerization. Based on detailed investigation of these factors, the optimal conditions for grafting were as follows: Fe²⁺, 1 × 10⁻³ mol/L; NBS, 1 × 10⁻² mol/L; MMA, 4%; pH, 2: polymerization time, 150 min; polymerization temperature, 60°C; material/liquor ratio, 1: 100. Under these optimal conditions, the rates of grafting of different vinyl monomers were in the following sequence: methyl methacrylate ≫ methyl acrylate > acrylonitrile. Other vinyl monomers namely, acrylic acid, and methacrylic acid have no ability to be grafted to the cellulosic fabric using the said redox system. A tentative mechanism for the polymerization reaction is suggested. © 1996 John Wiley & Sons, Inc.     

Redox-initiated vinyl graft polymerization onto wool with thiourea as the reductant. I. Grafting of methyl methacrylate with the hydrogen peroxide–thiourea catalyst system

The interaction of methyl methacrylate with wool under the catalytic influence of the hydrogen peroxide–thiourea redox system was studied under a variety of conditions. The degree of grafting depends upon the method empolyed; it is advantageous to first immerse wool in thiourea solution, monomer and hydrogen peroxide being then subsequently applied. Increasing the hydrogen peroxide concentration from 4 to 8 mmole/1. causes a significant enhancement in the graft yield. The latter remains practically unchanged upon further increment in hydrogen peroxide concentration within the range studied, i.e., up to 12 mmole/1. This was also observed with respect to thiourea concentration. On the other hand, increasing monomer concentration is accompanied by a significant increase in the graft yield. The polymerization reaction is temperature dependent; at the three temperatures examined, the graft yields follow the order 80° > 60° > 40°C. The rate of grafting is also dependent on the pH of the reaction medium over the range of 2 to 8, being decreased as the pH increased. Furthermore, the presence of traces of cupric ions in the polymerization system accentuates the graft formation. The alkali solubility as well as the urea bisulfite solubility of wool grafted with poly(methyl methacrylate) are much lower than those of physical mixtures of wool and poly(methyl methacrylate). This demonstrates that grafting of poly(methyl methacrylate) into wool has occurred.     

Grafting of Methacrylic Acid and Other Vinyl Monomers Onto Cotton Fabric Using Ce (IV) Ion–Cellulose Thiocarbonate Redox System

Graft copolymerization of methacrylic acid (MAA) onto cotton fabric using tetravalent ceric ion (Ce^IV)–cellulose thiocarbonate redox system was investigated under different conditions including pH of the polymerization medium (1–4), ceric sulphate (CS) concentration (4–20 m mole/l), MAA concentration (1%–6%), polymerization time (1/4–2 h) and polymerization temperature (0–70°C). Results obtained indicated that the optimal conditions for MAA grafting onto cotton fabric using the said redox system consisted of: [CS], 20 m mole/l; [MAA], 4%; pH of the medium, 2; time, 2 h; temperature, 60 °C keeping a material-to-liquor ratio at 1:0. Applying optimized conditions to different monomers, namely, acrylic acid (AA), methacrylic acid (MAA), acrylamide (Aam), acrylonitrile (AN), butyl acrylate (BuA), methyl methacrylate (MMA), ethyl methacrylate (EMA) and glycidyl methacrylate (GMA) onto the same substrate, the rates of grafting followed the order:

Photopolymerization of methyl methacrylate using benzoin isopropyl ether as photoinitiator: Effect of thiophenol compounds

Effects of a series of thiophenols R? ArSH with substituting groups R in the para-position and 2-mercaptobenzoic acid on the kinetics of polymerization of methyl methacrylate (MMA) photoinitiated by benzoin isopropyl ether (BIPE) were investigated using an autorecording dilatometer. Thiophenols were found to have a dual effect on polymerization: reducing induction time and accelerating rate of polymerization. A mechanism was proposed suggesting that this increased rate of polymerization and reduced induction time with addition of a thiophenol is due to the fact that, instead of consuming radicals, the dissolved oxygen in the MMA/BIPE system can be converted into active radicals through effective photooxidation of the thiophenol. Although the maximum increase in rate of polymerization is of a minor difference between various thiophenol compounds, reduction in induction time is strongly dependent on the nature of substituting groups in the following order: ? CH₃ > ? CH(CH₃)₂ > ? OCH₃ or ? Cl > ? H. 2-Mercaptobenzoic acid, on the other hand, increases induction time and decreases rate of polymerization. © 1993 John Wiley & Sons, Inc.     

Methyl Esters (Biodiesel) from and Fatty Acid Profile of Gliricidia sepium Seed Oil

Increasing the supply of biodiesel by defining and developing additional feedstocks is important to overcome the still limited amounts available of this alternative fuel. In this connection, the methyl esters of the seed oil of Gliricidia sepium were synthesized and the significant fuel‐related properties were determined. The fatty acid profile was also determined with saturated fatty acids comprising slightly more than 35 %, 16.5 % palmitic, 14.5 % stearic, as well as lesser amounts of even longer‐chain fatty acids. Linoleic acid is the most prominent acid at about 49 %. Corresponding to the high content of saturated fatty acid methyl esters, cold flow is the most problematic property as shown by a high cloud point of slightly >20 °C. Otherwise, the properties of G. sepium methyl esters are acceptable for biodiesel use when comparing them to specifications in biodiesel standards but the problematic cold flow properties would need to be observed. The ¹H‐ and ¹³C‐NMR spectra of G. sepium methyl esters are reported.     

In Situ Reflection–Absorption Infrared Spectroscopy at the Liquid–Solid Interface: Decomposition of Organic Molecules on Polycrystalline Platinum Substrates

The room-temperature adsorption and surface chemistry of several categories of organic molecules used as reactants or solvents in liquid-phase catalysis, of carboxylic acids, esters, aldehydes, acetone, alcohols and ethers in particular, were characterized in situ on polycrystalline Pt in the presence of the liquid phase by reflection-absorption infrared spectroscopy (RAIRS). For carboxylic acids and esters it was found that the propensity for decomposition and CO formation follows a formic acid ? methyl formate, ethyl formate > acetic acid, propionic acid, acrylic acid, ethyl acetate sequence. For aldehydes and acetone, the observed trend is formaldehyde ? acetaldehyde > acrolein, crotonaldehyde > propionaldehyde, acetone. Virtually no adsorbed CO was detected when Pt surfaces were exposed to liquid solutions of either alcohols or ethers. The observed trends could be correlated with the corresponding molecular structures. They are discussed in the context of previous results obtained from studies under ultrahigh vacuum (UHV) and under electro-oxidation conditions.     

The ferric hydroxide/hydrazine system as an initiator of vinyl polymerization

The reaction between ferric hydroxide and hydrazine was used to initiate the solution polymerization of methyl methacrylate. Polymerization occurs readily at pH > 6, over a wide range of iron concentration and of temperature. The initiation reaction appears to be of heterogeneous nature, like those in similar metal hydroxide/hydrazine systems.     

The lindlar-catalyzed reduction of methyl santalbate: a facile preparation of methyl 9-cis,11-trans-Octadecadienoate-9,10-d2

Conjugated linoleic acid (CLA) has been associated with the reduction of chemically induced cancers in mice and rats and the suppression of atherosclerosis in rats. We have found seed oils to be a valuable source of precursors for the rapid preparation of gram quantities of deuterium-labeled fats. Methyl santalbate (methyl 11-trans-octadecen-9-ynoate), obtained from Santalum album (Linn.) seed, was reduced with Lindlar catalyst, quinoline, and deuterium gas to produce, in yields of 65–75%, the gram quantities of methyl 9-cis,11-trans-octadecadienoate-9,10-d₂ (CLA-d₂) we required for metabolism and oxidation studies. Unlike monoacetylenic and methylene-interrupted polyacetylenic fatty acid methyl esters, the conjugated system was reduced with no noticeable break in the rate of deuterium uptake. The quantity of poison (quinoline) present did influence the amount of CLA-d₂ produced, but the production of overreduced fatty acid methyl esters (perhaps because of the conjugated system) could not be prevented. Fractionation of the reaction mixture by silver resin chromatography resulted in the isolation of >99% chemically pure CLA-d₂ in yields of 60–70%.