The reaction of picric acid with epoxides. II. The detection of epoxides in heated oils

A colorimetric method, based upon the reaction of the oxirane group with picric acid, was used to determine the epoxide content of heated vegetable oils. The picration method is particularly suitable for measuring small quantities of epoxide because it is much more sensitive than the common titrimetric methods, and it is not subject to interference from cyclopropene, conjugated dieneols, or α, β-unsaturated carbonyls. Thin-layer chromatography was used to separate mixtures of picrated, epoxidized methyl esters. Separation ofcis- andtrans-methyl epoxystearate, methyl epoxyoleate, and methyl diepoxystearate in a mixture of these four esters was achieved in this manner. The presence of saturatedcis- andtrans-epoxystearates and unsaturated epoxides was demonstrated in heated vegetable oils. Presented, in part, at the AOCS Meeting in Cincinnati, October 1965.     

A rapid sensitive colorimetric method for the determination of ascorbic acid

A new colorimetric procedure based on the interaction of ascorbic acid with 4,4′-dimethoxydiquinone (I) in an aqueous dioxane solution was developed. In this procedure the diquinone reagent (I) is reduced to a blue-violet product (II)¹ which absorbs maximally at 490–500 nm. The colour development takes place within 6 min at 25°C and absorbance vs concentration was linear up to a sample size of 600 μg. Reducing substances likely to be present in biological fluids or in natural extracts of the vitamin do not interfere with colour development and average recoveries of 99.8 ± 0.4% were obtained for solutions containing these substances.     

Onset of convective burning in picric acid

Based on simultaneous optical registration and measurement of the pressure at several points along the height of a sample, we have studied the onset of convective burning in picric acid when it is ignited from a closed end. We have investigated the effect of the particle size and density of the explosive (0.7–1.1 g/cm³), the height of the sample, the power of the igniter, and the parameters of the channel in the shell. We have obtained the spatial profiles of the pressure distribution. We have determined the dependence on the investigated parameters of the critical height of the bed at which convective burning begins. We have determined two typical cases realized in the initial stage of development of the process. For one case, a smooth increase in pressure before and after the luminosity front is characteristic; for the other case, the presence of a peaked pressure distribution close to the front is characteristic. We have established the conditions under which a specific case is realized. We suggest an explanation for the results obtained.N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, Moscow 117977. Translated from Fizika Goreniya i Vzryva, Vol. 31, No. 1, pp. 26–32, January–February, 1995.     

Direct cleavage of internal epoxides with periodic acid

Reaction of methyl esters of epoxidized fatty acids with paraperiodic acid led to direct cleavage of epoxide functions and the production of aldehydes and methyl azelaaldehydate. The reaction was carried out in aqueous dioxane. The use of other solvents and the influence of reaction variables was examined. The reaction is essentially quantitative for methyl, 9,10-epoxystearate. Presented at the AOCS Meeting in Cineinnati, October 1965. E. Utiliz. Res. Dev. Div., ARS, USDA.     

The reaction of kaolin with fluorides: I. Effect of neutral and acid sodium fluoride solutions

The reaction between kaolinite and neutral and acid sodium fluoride solutions was investigated at different temperatures and over the acid pH range. The stoicheiometric replacement of hydroxyls in the kaolinite crystal lattice by fluoride ions, as reported by earlier workers, was not confirmed. The release of hydroxyl ions into solution was due predominantly to the disruption of the kaolinite crystal lattice. In the presence of sodium ions and at pH < 7, sodium fluoro-silicate and cryolite were found as solid phases. At pH > 7, only cryolite was found as a solid phase. Small, spherical, particles were observed in all cases. These particles were believed to be amorphous silica, formed as an intermediate phase in the disruption process.     

脱硫液中苦味酸含量的测定

通过苦味酸与结晶紫缔合,利用环己烷萃取,采用分光光度法直接测定脱硫液中苦味酸的浓度,从而建立了1种测定脱硫液中苦味酸的新方法。经过对脱硫液进行加标回收试验表明,加标回收率为103-3％,说明混合体系中杂质对测定干扰小,该方法对测定脱硫液中苦味酸的浓度比较准确。     

The iodide iodate reaction method: The choice of the acid

Mixing processes are frequently characterized with competing chemical reaction schemes. The most popular reaction scheme for continuous flow mixers is the iodide iodate reaction method, which traditionally uses sulfuric acid as proton source for both reactions involved in the scheme. Experimental evidence is provided which indicates that for a quantitative treatment of the experimental data either the experiments need to be carried out with a strong acid such as perchloric acid or the dissociation constants of sulfuric acid need to be included in the models linking the primary experimental results with quantitative measures such as mixing times. Another chemical test reaction system, the acetal cleavage method, traditionally carried out with hydrochloric acid was applied for comparison. In that case, the use of perchloric acid showed no significant impact on the experimental results.     

顶空-气相色谱法测定水中苦味酸

建立了顶空-气相色谱法测定水中苦味酸的基本方法,运用苦味酸与次氯酸钠的衍生化反应,经顶空进样器直接进样,保留时间定性,外标法定量,得到了较好的分离效果,以及较高的灵敏度、精密度和回收率。该方法在0~50μg/L范围内线性良好(R=0.999 2),检出限为0.18μg/L,相对标准偏差为1.76%~4.29%,加标回收率为91.22%~108.95%,适合生活饮用水及其水源地水和废水中苦味酸的测定。     

Mechanism of lipoxidase reaction. I. Specificity of hydroperoxidation of linoleic acid

Linoleate hydroperoxides from autoxidation of methyl linoleate and from lipoxidase oxidation of linoleic acid are compared. Data indicate an equal amount of methyl 9- and 13-hydroperoxyoctadecadienoate produced by autoxidation of methyl linoleate, and the exclusive formation of 13-hydroperoxyoctadeca-9,11-dienoic acid from the incubation of lipoxidase with linoleic acid. As a result of these findings, a specific mechanism for the reaction of lipoxidase with linoleic acid is postulated. Presented at the AOCS Meeting, Philadelphia, October 1966. This work was conducted under a Postdoctoral Resident Research Associateship established at the Northern Laboratory by ARS, USDA, in association with the National Academy of Sciences-National Research Council. No. Utiliz. Res. Dev. Div., ARS, USDA.     

A new colorimetric method for estimation of argemone oil

Argemone oil is toxic even in low concentrations for human consumption. The author suggests a new colorimetric method in which an orange color is developed when antimony trichloride solution is added to the extracted alkaloid. The developed color is measured in a colorimeter and compared against known standards of the alkaloid. The alkaloid content of argemone oil has been found to be about 1.0%. This method determines an admixture of argemone oil as low as 0.005% in other edible oils.     

Meso-tetraarylporphyrin catalyzed highly regioselective ring opening of epoxides with acetic acid

Highly regioselective ring opening of styrene oxide with acetic acid in the presence of catalytic amounts of meso-tetra(4-CH₃)phenyl- or meso-tetraphenylporphyrin at room temperature is reported. Under the same reaction conditions, cyclohexene oxide is more reactive than styrene oxide and gives the trans-isomer as the sole product.     

The reaction of kaolin clay with orthophosphoric acid

Conclusions Orthophosphoric acid reacts with kaolinite clay already at room temperature. The reaction results in the dissociation of some kaolinite and the formation of acid aluminophosphates, its rate is at maximum during the first 4–10 days of the storage of the composition of clay with the acid, and it ceases when the composition is stored for longer periods.The triderivative of aluminophosphate begins to form only on heating above 100°C. At a temperature of 400°C and higher it forms more rapidly while the proportion of mono- and diderivatives of aluminophosphates diminishes.The fact that in compositions of kaolinite clay with orthophosphoric acid in storage only water-soluble acid aluminophosphates are formed and triderivative of aluminophosphate is absent makes it possible to produce clay-containing aluminosilicate compositions containing orthophosphoric acid at refractory plants in ready-for-use form.Translated from Ogneupory, No. 7, pp. 43–48, July, 1977.     

The reaction of ethylene oxide with oleic acid

The base-catalyzed reaction of ethylene oxide with oleic acid can be divided into two stages. The first stage consists of a slow reaction of oleic acid with ethylene oxide to form principally ethylene glycol monooleate; other reactions such as esterification, transesterification and polyglycol formation lag behind. In the second stage, after the addition of approximately one mole of ethylene oxide, the reaction accelerates and transesterification equilibrium is rapidly attained. The composition of products containing several molecules or more of ethylene oxide can be calculated satisfactorily on the assumption of random addition of ethylene oxide and random esterification of the hydroxyl groups. The uncatalyzed reaction is much slower and transesterification equilibrium is attained slowly, if at all. A reaction mechanism based on the difference in basicities of the carboxylate and alkoxide ions (and the relative rates of the competitive ethylene oxide reactions) is presented for the base-cat-alyzed reaction.     

The reaction of kaolin with fluorides. II. Effect of aqueous hydrofluoric acid

The dissolution of kaolinite in aqueous solutions of hydrofluoric acid was investigated at different temperatures and fluoride concentrations. The percentage dissolution of kaolinite was greater than was to be expected from a theoretical consideration of the reaction. The percentage dissolution was less for Na-kaolinite than for a H-kaolinite under the same experimental conditions. Two reaction rates were observed. The relative intensities of the 001 and 002 basal reflections decreased with reaction time, temperature and hydrofluoric acid concentration. The decrease was probably due to an amorphous phase. Although kaolinite samples after treatment at the lower temperature showed very little change in their infra-red absorption spectra, a marked change in the spectra was observed at the higher temperature. The disruption of the kaolinite crystal lattice is believed to be due to the preferential extraction of aluminium from the lattice leaving an intermediate silica phase, which dissolves to form fluorosilicic acid.     

The reaction of mercaptoacetic acid with methyl linoleate and linoleic acid

The reaction of mercaptoacetic acid with methyl linoleate and with linoleic acid was investigated. The reaction proceeded at low and erratic rates, with and without catalysts, such as peroxides at various temperatures, but could be accelerated by use of a large excess of mercaptoacetic acid. Addition of 1 mole of mercaptoacetic acid to 1 mole of methyl linoleate resulted in a product containing about 40% of mono-adduct. Ozonolysis of the purified mono-adduct yielded approximately equimolar quantities of caproic and azelaic acids, indicating that addition occurred about equally at the 9,10- and 12,13-ethylenic bonds. The dicarboxylic acid and the dimethyl ester of the mono-adduct and the tricarboxylic acid and trimethyl ester of the di-adduct of linoleic acid and mercaptoacetic acid were prepared, and the infrared spectra and some physical and chemical characteristics of these products were determined. The infrared spectra of the reaction products were obtained and correlated with functional groups which give rise to them. Bands at about 7.8 and 8.8 μ, commonly observed in long chain acids and esters and ascribed to C−O vibrations, are intensified in the sulfur-containing reaction products, suggesting characteristic absorption of C−S compounds at almost identical wavelengths. The formation of adducts was accompanied by a high degree of isomerization of the unreacted ethylenic bonds from thecis to thetrans form both in the mono-adduct and in unreacted methyl linoleate. The methyl linoleate recovered contained about 12% diene conjugation, but catalytic quantities of mercaptoacetic acid were not effective in inducing conjugation.     

Disproportionation of abietic acid: I. Iodine catalyzed reaction at low temperature

Disproportionation of abietic acid in the presence of equimolar iodine was carried out in benzene at 60 C, and the reaction products were continuously determined by gas-liquid chromatography as methyl esters. The major peaks were isolated and characterized by mass, infrared, and nuclear magnetic resonance spectrometry. Four isomers of dihydroabietic acids, dehydroabietic acid, and small amounts of lactones were detected. Electron spin resonance measurement suggested the intermediacy of free radicals.     

The reaction between ethylene and chlorine-water in a wetted-wall column. I. The mechanism of reaction

A wetted-wall column was used to measure rates of sorption of ethylene into the following liquids: pure water, aqueous hypochlorous acid, and chlorine-water acidulated with hydrochloric acid. Experimentally determined diffusivities of ethylene in water, at 20° and 30°, are consistent with previously reported values. The experimental evidence supports Shilov's mechanism viz., that the reaction between ethylene and chlorine-water takes place via a liquid-phase complex of ethylene and free chlorine.