Preparation of polysiloxanes from silicic acid. VII. Effects of the degree of esterification and alkyl groups on condensations of silicic acid esters and formation of fibrous silica

Silicic acid esters were prepared by the reaction of the silicic acid in tetrahydrofuran with various alcohols such as such as methanol, ethanol, 2-propanol, 1-butanol, 2-methyl-2-propanol and 1-octanol, using an esterification apparatus designed especially to allow the preparation of silicic acid esters from alcohols with low boiling points or appreciable steric hindrance. With the intent of obtaining a spinnable ester solution by condensation of silicic acid esters, the effects of the degree of esterification (DE) and alkyl group on gel time and spinnability are investigated. An increase in the DE and the size of the alkyl group led to an increase in the gel time of the esters. Esters solutions with a good spinnability were prepared from n-butyl and isopropyl esters with DEs of 40–50%. In addition, the gel permeation chromatography of condensing esters with low DEs showed a rapid increase in molecular weight. The results showed that spinnability depended on DE and the ester's alkyl group. Fibers could be formed with length of about 10–100 cm from ethyl, isopropyl, and n-butyl esters with DEs 40–50% and with length of 10 cm from octyl ester with DE 26%.     

Preparation of polysiloxanes from silicic acid. V. Condensation of silicic acid butyl esters and formation of silica fiber from the ester solutions

The condensation of silicic acid butyl esters was investigated by gel permeation chromatographic (GPC) analysis. The results revealed that the condensation was greatly dependent on a degree of esterification of the esters. The ester with the lowest degree of esterification underwent condensation to form a highly polymerized ester. It was found that fibers could be drawn from the ester solution before gelation.     

Dynamic kinetic resolution of racemic tropic acid ethyl ester and its derivatives

The dynamic kinetic resolution of racemic mixtures of tropic acid ethyl ester under substrate racemizing conditions was studied using lipase PS with a ruthenium catalyst. Isopropenyl acetate was used as an acyl donor, since it was found to be compatible with both catalysts; this resulted in an efficient dynamic kinetic resolution. With this process, a variety of racemic tropic acid ethyl esters were transformed to optically active acetoxy-2-arylpropionic acid ethyl esters with 60-88% yields and 53-92% ee.     

Preparation and thin-layer chromatography of bromo-derivatives of unsaturated fatty acid esters. A simple and rapid procedure for fatty acid analysis.

Bromo-addition products of unsaturated long-chain fatty acid esters have been prepared and chromatographed on thin layers of unmodified silica gel. The polarity of these derivatives was found to be directly related to the number of double bonds of the parent fatty acid from which they were derived. This has been made the basis of a simple method for assessing the relative proportions of the main fatty acid classes in a mixture.     

Preparation of single-enantiomer semiochemicals using 2-methoxy-2-(1-naphthyl)propionic acid and 2-methoxy-2-(9-phenanthryl)propionic acid

Enantioresolution of 3-octanol, 6-methyl-5-hepten-2-ol (sulcatol), and 1-octen-3-ol was conducted using (S)-(+)-2-methoxy-2-(1-naphthyl)propionic acid (MαNP acid) and (S)-(+)-2-methoxy-2-(9-phenanthryl)propionic acid (M9PP acid). In each case, the diastereomeric esters obtained were readily separated by HPLC. The stereochemistry of the esters could be assigned from their respective ¹H NMR analyses. Solvolyses of the esters gave enantiopure alcohols and acids. MαNP and M9PP acids displayed almost equivalent properties in ¹H NMR anisotropy. The chiral resolving ability of M9PP acid was slightly superior to that of MαNP acid in HPLC.     

Thin-layer chromatography of steroids. X. RM-correlations of cholesterol esters,ethers, carbonic acid esters and halogen derivatives

A study was made of the TLC properties of the 3-beta-substituted esters, ethers, carbonic acid esters and halogen derivatives of cholesterol.As regards the TLC properties it can be stated as a general correlation that the same solvent systems are suitable for the separation of these groups of compounds (with the exception of the halogen derivatives). As a result of our experiment, four such systems could be found among many others tried.A regularity can be observed with regard to the polarity change of the esterifying component from C₆ to C₁₆ in the cyclohexane-chloroform (6:4) system.The cholesterol 3-beta-ethers are more polar than the esters, but with the lengthening of the etherifying side-chain the polarity decreases more rapidly than in the case of the esters; from the point of a TLC separation technique this is a very advantageous property.As regards their properties the cholesterol carbonic acid derivatives can be correlated with the cholesterol ethers.Compared with the above groups the 3-beta halogen cholesterol derivatives exhibit different properties. Their separation can be achieved with apolar solvents.     

Water-Soluble imide-amide copolymers. II. Preparation and characterization of poly (acrylamide-co-p-maleimidobenzoic acid)

The comonomer required, p-maleimidobenzoic acid (MBA) was first prepared in good yield by refinements of published methods. p-Carboxysuccinanilic acid (CSA), and p-succinimidobenzoic acid (SBA), were also prepared to provide models useful for IR and NMR for spectroscopic assignments of the new copolymers. Polymerization of MBA with acrylamide in glacial acetic acid at 60°C gave copolymers with estimated viscosity average molecular weights of 60,000 to 90,000. Yields and viscosity average molecular weights decreased as the MBA to acrylamide monomer feed ratio was increased. The rate of incorporation of MBA into the copolymer rose from 7 to 23% when the mole ratio in the feed was raised from 5 to 20%. Decreasing the initiator concentration increased molecular weights by less than predicted and reduced the yield of copolymer for any given feed ratio of MBA to acrylamide. In all cases about 30–40% of the MBA units in the purified copolymers were hydrolyzed. A change to dimethyl sulfoxide solvent gave good, and poor yields of copolymer at 5 and 10 mol % MBA, respectively, and no copolymer at 20 mol % MBA. Viscosity average molecular weights of the copolymer products prepared in DMSO were somewhat lower than obtained for the copolymers prepared in acetic acid. Polymerization in a DMSO-water mixture gave a negligible yield of polymeric product. Instead, only hydrolysates of MBA precipitated when the coloured polymerization solutions were added to methanol.     

Chiral separation by electrokinetic capillary chromatography using newly synthesized linear polymers containing L-amino acid moieties.

Chiral linear polymers were prepared by the thermal polymerization of N-acryloyl-L-valine and N-acryloyl-L-alanine derivatives using 3-mercaptopropionic acid (3-MPA) as a radical transfer agent. C-Terminal groups of the derivatives were methyl and tert-butyl esters later removed, and N-methylamide moieties. The N'-methylamide derivative of N-acryloyl-L-valine was copolymerized with methyl ester at a molar mixing ratio of 1:1. The ester groups were removed to provide anionic linear polymers terminated with carboxylic acid of the amino acid residue. The polymers are thus shown to function as pesudostationary phases that separate enantiomeric solutes in electrokinetic capillary chromatography (EKC). Racemic 3,5-dinitrobenzoylamino isopropyl esters were separated with the polymer derived from N-acryloyl-L-valine esters and with the copolymer from N-acryloyl-L-valine methyl ester and N-acryloyl-L-valine N'-methylamide at pH 7.0. These separations could not be observed at pH 9.0 in migrating solutions containing anionic linear polymers. This pH dependence can be discussed from the standpoint of the microscopic hydrophobicity of the polymers, as assessed from the fluorescence of pyrene adsorbed onto the polymers in water.     

Synthesis and thermal self-crosslinking reaction of polymer containing spiro ortho ester and carboxylic acid

Polymers with both pendant spiro ortho ester and carboxylic acid moieties were synthesized by partial esterification of poly(methacrylic acid), poly(methacrylic acid-co-methyl methacrylate), or poly(methacrylic acid-co-styrene) with halomethylated spiro ortho esters in the presence of 1,8-diazabicyclo[5,4,0]undecene-7 in dimethyl sulfoxide. The extent of esterification increased with increasing reaction temperature. The reaction of polymeric carboxylic acids with chloromethylated spiro ortho esters proceeded to 80% of conversion at 100°C for 120 h. In contrast, the degree of esterification with bromomethylated spiro ortho ester reached 80% at 60°C within 24 h. Thermo-crosslinking of polymers having pendant spiro ortho ester moiety and carboxylic acid could be effected in films. The rate of spiro ortho ester ring-opening increased with increasing reaction temperature and with increasing content of carboxylic acid groups in the polymer. Further, the rates of gel production were also measured. The polymer containing an equimolar mixture of spiro ortho ester moieties and carboxylic acids exhibited the highest reactivity. In addition, it was found that thermal crosslinking reaction of the polymer occurred with minimum volume shrinkage.     

3-Oxo-1,2-benzoisothiazoline-2-acetic acid 1,1-dioxide derivatives. I. Reaction of esters with alkoxides

Reaction of 3-oxo-1,2-benzoisothiazoline-2-acetic acid alkyl esters 1,1-dioxide ( 1a-d ) with alkaline alkoxides was carried out under various conditions. Under mild conditions, o-(N-carboxymethylsulfamyl)benzoic acids dialkyl esters ( 2a-d ) were obtained with good yields. Reaction of 1a-d or 2a-d with sodium alkoxides under drastic conditions afforded 4-hydroxy-2H-1,2-benzothiazine-3-carboxylic acid alkyl esters 1,1-dioxide ( 3a-d ). Transesterification was observed when esters 1b-d were treated with sodium methoxide in methanol. Esters 3a-d were hydrolyzed in concentrated aqueous sodium hydroxide affording the acid 6 . Attempts to recrystallize 6 from water resulted in its decarboxylation to give 2H-1,2-benzothiazine-4-(3H)one 1,1-dioxide (7). Compound 6 could not be obtained by acid hydrolysis of esters 3a-d or by rearrangement of 3-oxo-1,2-benzoisothiazoline-2-acetic acid 1,1-dioxide ( 8 ). Different experimental evidence supports the suggestion that rearrangement took place by ethanolysis of the carboxamide linkage affording the open sulfonamides (fast step) followed by a Dieckmann cyclization (slow step). It was demonstrated that transesterification took place in the open sulfonamides 2 .     

Functional polymers. II. Preparation and polymerization of methyl 5-vinylsalicylate,methyl 5-vinylacetylsalicylate, 5-vinylsalicylic acid,and 5-vinylacetylsalicylic acid

Four new derivatives of 5-vinylsalicylic acid were prepared and their homopolymerization and copolymerization with acrylic acid and methacrylic acid investigated. Methyl 5-vinylsalicylate was prepared in a six-step synthesis from methyl salicylate in an overall yield of 35%. Acetylation in the last step yielded methyl 5-vinylacetylsalicylate. Hydrolysis of methyl 5-vinylsalicylate gave 5-vinylsalicylic acid which was acetylated to 5-vinylacetylsalicylic acid (5-vinyl aspirin). The 5-vinyl-substituted salicylic acid derivatives could be readily homopolymerized and copolymerized with acrylic acid and methacrylic acid to give various compositions of copolymers. It is worth noting that even the monomers with free phenol groups could be readily polymerized with azobisisobutyronitrile as radical initiator to high molecular weight polymers without interference of the phenolic OH group.     

Preparation of synthetic auxin-amino acid conjugates

Auxin amide conjugates are regulators of the most important auxin, indole-3-acetic acid (IAA), which is considered responsible for many important processes within the plants. Herein, amide conjugates of IAA were synthesized employing a simple and efficient coupling method with WSCI·HCl, a water-soluble condensing reagent, in the presence of 1-hydroxybenzotriazole. IAA conjugates with 10 amino acids along with their corresponding methyl esters were prepared in excellent yields, up to 95%, aiming to facilitate their identification in plant species. Eight IAA-amino acid methyl ester conjugates are characterized here for the first time.     

Gas-liquid chromatography of saturated fluorinated carboxylic acid esters 1. Retention in homologous series

The retention times were determined for the first time for the members of 12 homologous and pseudohomologous series of polyfluorinated carboxylic acid esters on SE-30 and SKTFT-50Kh phases in isothermal conditions in the 60–160°C temperature range. It was found that the contributions of the methylene and difluoromethylene groups to the retention times change nonlinearly with an increase in the atomic number of the homolog. The suitability of three correlation equations for describing the Chromatographic behavior of polyfluorocarboxylic acid esters was assessed.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 418–425, February, 1991.     

Specific assay for homoserine and its lactone in Pisum sativum. Preparation of homoserine hydroxamic acid

The existence of homoserine lactone in Pisum sativum seedlings is demonstrated. L-Homoserine lactone reacts with hydroxylamine, at neutral or alkaline pH, to form homoserine hydroxamic acid. Procedures are described for preparing L-homoserine lactone and L-homoserine hydroxamic acid. The hydroxamic acid yields a color with maximum absorbance at 492 nm with Fe³⁺ in 0.25 N HCl. This reaction permitted assay for total homoserine and homoserine lactone. Six-day old Pisum sativum seedlings, with cotyledons removed, were extracted with 90% ethanol. Evaporation of the ethanol and addition of Na₂SO₄ solution and toluene and centrifugation removed protein lipids and esters. After clarification with activated charcoal, homoserine lactone content was estimated by reaction with NH₂OH and Fe³⁺ reagents. For total homoserine, protein precipitation was with 2 N HCl and toluene. Evaporation to dryness at 60 °C under vacuum converted all homoserine to the lactone. The values found for total homoserine (μmols/g, wet weight) and preformed lactone (%) with the various growth media used were as follows: nitrate 87.4 (14.7%), NH₂OH 75.2 (6.3%), water 70.5 (7.9%), urea 56.4 (18.9%). Acetic anhydride added to homoserine hydroxamic acid forms acetohydroxamic acid, which yields a color with maximum absorbance at 505 nm with Fe³⁺. This color reaction is seven times as sensitive as the reaction of Fe³⁺ with homoserine hydroxamic acid itself.     

Quantification of primary fatty acid amides in commercial tallow and tallow fatty acid methyl esters by HPLC-APCI-MS

Primary fatty acid amides are a group of biologically highly active compounds which were already identified in nature. Here, these substances were determined in tallow and tallow fatty acid methyl esters for the first time. As tallow is growing in importance as an oleochemical feedstock for the soap manufacturing, the surfactant as well as the biodiesel industry, the amounts of primary fatty acid amides have to be considered. As these compounds are insoluble in tallow as well as in the corresponding product e.g. tallow fatty acid methyl esters, filter plugging can occur. For the quantification in these matrices a purification step and a LC-APCI-MS method were developed. Although quantification of these compounds can be performed by GC-MS, the presented approach omitted any derivatization and increased the sensitivity by two orders of magnitude. Internal standard calibration using heptadecanoic acid amide and validation of the method yielded a limit of detection of 18.5 fmol and recoveries for the tallow and fatty acid methyl ester matrices of 93% and 95%, respectively. A group of commercially available samples were investigated for their content of fatty acid amides resulting in an amount of up to 0.54%m/m (g per 100 g) in tallow and up to 0.16%m/m (g per 100 g) in fatty acid methyl esters.     

Synthesis of erythro-alpha-amino beta-hydroxy carboxylic acid esters by diastereoselective photocycloaddition of 5-methoxyoxazoles with aldehydes

A new photoaldol route to alpha-amino-beta-hydroxy carboxylic acid esters is initiated by the photocycloaddition of aromatic or aliphatic aldehydes to 5-methoxyoxazoles. The 4-unsubstituted 5-methyloxazole 1 gave the cycloadducts 8a-f in high yields and excellent exo-diastereoselectivities. Hydrolysis of 8a-f gives the N-acetyl alpha-amino-beta-hydroxy esters 9a-f, which could be subsequently converted into the corresponding Z-didehydro alpha-amino acids 10a-f. Quartenary alpha-amino-beta-hydroxy esters 12, 14, 16, 18, and 20, which are stable against dehydration, were obtained from the 4-alkylated 5-methoxyoxazoles 2-6, in most cases highly erythro-selective due to the high degree of stereocontrol (exo) at the photocycloaddition (to give 11, 13, 15, 17, and 19) level. The relative configurations of the N-acetyl alpha-amino-beta-hydroxy esters were determined by NMR spectroscopy and comparison with chiral pool-derived compounds as well as by X-ray structure determination of the ester 23, formed by hydrolysis of the cycloadduct 22, derived from photocycloaddition of propionaldehyde to the isoleucine-derived oxazole 21.     

Micro-determination of total phthalate esters in biological samples by gas-liquid chromatography.

A method was investigated in which all of the phthalate esters in biological samples were determined as phthalic acid by gas-liquid chromatography. The method is based on the separation of phthalate esters from the sample with n-hexane, saponification of the esters with an alkaline ethanolic solution to give phthalic acid, purification of the acid by extraction with diethyl ether and column chromatography using silica gel, and conversion of the acid into bis(2,2,2-trifluoroethyl) phthalate with a 2,2,2-trifluoroethanol solution containing boron trifluoride. The derivative obtained is highly sensitive to an electron-capture detector, giving a sensitivity of 0.1 pg. Biological samples fortified with di(2-ethylhexyl) phthalate at levels of 5-100 ppb were analyzed, with recoveries of 70-100%.     

Functional polymers. VI. Preparation and polymerization of methyl 3-vinylsalicylate,methyl 3-vinylacetylsalicylate, 3-vinylsalicylic acid,and 3-vinylacetylsalicylic acid

The title compounds were synthesized and their homopolymerizations and copolymerizations with styrene and a number of acrylic monomers were investigated. Methyl 3-vinylacetylsalicylate was prepared in a five-step synthesis from 2-ethylphenol in an overall yield of 40%. Methanolysis of this compound gave methyl 5-vinylsalicylate in 63% yield. Hydrolysis of methyl 3-vinylsalicylate gave a nearly quantitative yield of 3-vinylsalicylic acid which could be acetylated to 3-vinylacetylsalicyclic acid (3-vinyl aspirin). 3-Vinylsalicylic acid derivatives were readily homopolymerized and copolymerized with styrene, methyl methacrylate, and methacrylic acid, and 3-vinylsalicyclic acid was copolymerized with a number of vinyl and acrylic monomers. Copolymer compositions were determined by examination of ¹H-NMR spectra.     

麻疯油转酯化产物的高效液相色谱分析

建立了高效液相色谱法同时测定麻疯油转酯化产物中4种主要脂肪酸甲酯的分析方法。样品经膜处理后用丙酮溶解,采用Hypersil ODS(C18)色谱柱进行分离。以乙腈为流动相进行等度洗脱,内标法定量,同时对色谱条件进行优化。结果表明,在优化的色谱条件下4种脂肪酸甲酯在10 min内得到良好的分离,标准曲线的线性相关系数均达到0.999以上,平均回收率为96%~98%,重现性相对标准偏差为7.2%~10.2%,重复性相对标准偏差为0.31%~2.02%。与气相色谱法相比,该方法具有较高的灵敏度,可用于麻疯油转酯化产物中脂肪酸甲酯含量的测定,为麻疯油转酯化反应制备生物柴油的定性定量分析提供了参考依据。     

Characterization of Saccharomyces Sp. through determination of amino acid profiles by capillary gas chromatography

The Saccharomyces strains uvarum, montuliensis, bayanus, capensis and florentinus were grown in liquid media prepared from a 1% aqueous glucose solution to which 0.05% of ammonium sulfate or urea were added as the only nitrogen supply. The amino acids exuded during incubation were isolated by cation exchange and derivatized as the corresponding N,O-heptafluorobutyryl isopropyl esters. Separation was achieved on a highly deactivated glass capillary column coated with OV-101. A characteristic amino acid profile was obtained for each of the species studied, allowing the construction of a chemotaxonomic tree, on the basis of present or absent acids.