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[en] This paper is a discussion of two reports. One, issued in April 1990, addresses gasoline octane mislabeling, and the other, issued in February 1991, addresses possible consumer overbuying of premium gasoline. Consumers can purchase several grades of unleaded gasoline with different octane ratings regular (87 octane), mid-grade (89 octane), and premium (91 octane or above). A major concern of consumer buying gasoline is that they purchase gasoline with an octane rating that meets their vehicles' octane requirements. In summary, it was found that consumers may unknowingly be purchasing gasoline with lower octane than needed because octane ratings are mislabeled on gasoline pumps. At the same time, other consumers, believing they may get better performance, may be knowingly buying higher priced premium gasoline when regular gasoline would meet their vehicles' needs. These practices could be coasting consumers hundred of millions of dollars each year
[en] Highlights: • Extremely flat twisting potential is predicted for DABCO. • M11 and MN12-SX functionals are recommended. • Entropic effects play important role in stabilization of twisted conformers. The energy and structural parameters of 1,4-diazabicyclo[2.2.2]octane (DABCO) obtained by various DFT methods are examined versus ab initio and experimental data. The features of twisting potentials of DABCO and closely-related species (1-azabicyclo[2.2.2]octane and bicyclo[2.2.2]octane) are discussed in light of computational schemes applied.
[en] In the present work, chemometric methods were used for investigations of crude oils and petroleum products by statistical evaluation of spectroscopic data. The spectroscopic information was obtained by 1H-Nuclear Magnetic Resonance and infrared experiments. Research octane numbers (RON) and motor octane numbers (MON), representing important characteristics for knocking behavior,were calculated by multilinear regression. In the period of two years it was tested whether the precision of such models was negatively influenced by varying chemical composition of the commercial gasoline. A Partial Least Squares model (PLS) was created to calculate MON. The model based on infrared spectroscopic data in the spectral region of 1400 to 650 cm1. The standard deviation between PLS-method and the standard method ASTM D 2700 was 0,6. Another PLS-model in combination with spectroscopic data was used for calculating cetane numbers of diesel fuels. Using the spectral region of 1650 to 650 cm1 the content of the cetane improver 2-ethyl-hexyl-nitrate could be detected. A standard deviation of 1,8 to ASTM D 613 has been achieved. An additional aim of the work was to identify crude oils by the means of principal component analysis of spectroscopic data in the near infrared region. The investigations included the determination of negative effects on data acquisition like varying temperature, water-, salt-, and sediment content. Furthermore, the density and the boiling yields in distillation of crude oils were calculated with PLS-models. (author)
[en] A versatile and efficient synthetic route to pheromones with 6,8-dioxabicyclo octane structure was developed as frontalin was synthesized in 7 steps with 30% overall yield and brevicomins were synthesized in 6 steps with 15% overall yield. The enantiomeric ratios of these pheromones were also controlled by applying asymmetric dihydroxylation reaction with varying temperature conditions. Thus, the current synthetic route will be readily applied to the synthesis of various analogs of these pheromones and to study the effect of enantiomeric ratios of these pheromones in communications among beetles and elephants. 6,8-Dioxabicyclo octane is a core structure of many natural products possessing various biological activities with wide structural diversity, and thus is considered one of privileged structures. Among these natural products, relatively simple derivatives such as frontalin and brevicomins are not only major bioactive component of the aggregation pheromones of beetles but also long sought pheromones in mammalians as they are secreted by elephants. While these pheromones exhibit biological activity only as a single enantiomer in beetles, the same pheromones secreted by elephants with varying ratio of enantiomers depending on elephant's age and musth show different sexual behavior and aggressions. While various synthetic route to the total synthesis of frontalin and brevicomins have been reported, we became interested in devising a versatile and efficient synthetic route to these pheromones and their analogs with varying enantiomeric ratio for future study on structure activity relationship and e. r. activity relationship
[en] Single-channel coaxial segments were used for the introduction of an aqueous or octan-1-ol solution of an organic substance directly into a continuous flow of the other solvent. The analytical signal was measured simultaneously on both aqueous and organic phase segments by an 'on-tube' fast-reading spectrophotometric detector (ca. 3 ms time resolution) and treated mathematically. The octan-1-ol-water phase signal ratio corresponds to the partition coefficient of the organic substances. The applicability of the method is demonstrated by the determination of partition coefficients of phenol, citric acid, acetylsalicylic acid and sodium salicylate. (author). 8 refs.; 3 figs.; 1 tab
[en] The positron annihilation technique was applied to the study of the micelle formation process in reversed micellar systems, Aerosol OT and dodecylammonium propionate in apolar solvents, such as benzene, isooctane, and cyclohexane. The results indicate that the positronium formation probability responds very sensitively to microphase changes in reversed micellar solutions. The abrupt changes in positronium formation probability observed at certain surfactant concentrations appear to coincide with variations in the aggregation state of the surfactant molecules in solutions, as postulated by the modified pseudophase model which considers the possibility of conformational changes between premicellar aggregates, and the surfactant concentrations at which they occur may be interpreted as operational critical micelle concentrations. Additives or probe molecules can affect these changes and shift them to lower surfactant concentrations. The additions of H2O and its solubilization in form of clusters inside the reverse micelle leads to microphase changes also detectable by the positron annihilation technique. From a comparison of the rate constants between positronium and probe molecules observed in the neat solvents and in the corresponding micellar solutions, it was concluded that the probe molecules are attracted to various degrees by the reverse micelles, the nature of the surfactant and solvent determining the relative distribution of the probe molecule in the outer hydrocarbon layer and in the bulk apolar solvent of the reversed micelles
[en] The coexistence curves of (T, n) (T, φ) and (T, ψ) (n, φ, ψ are the refractive index, the volume fraction, and the effective volume fraction, respectively) for two ternary nonaqueous microemulsion systems have been determined at constant pressure and a constant molar ratio ω of DMA to AOT. The critical exponent β and the critical amplitude B have been deduced, and the values of β were consistent with the theory of 3D-Ising in a region sufficiently close to the critical temperature. The results show that the coexistence curves have been successfully described by the Wegner equation and the expression for the diameter
[en] Highlights: • The authors neglected the contribution of binary systems. • Using the Redlich–Kister equation, with or without the ΔV_i_j binary contributions. • Lower σ deviations if the ΔV_i_j binary and ΔV_i_j_k ternary contributions are used. - Abstract: This short communication presents the response to the comments published by William E. Acree Jr., Thermochim. Acta (2015), regarding the use of the equation Redlich and Kister by C. Lisa and collaborations in calculating the excess molar volume for ternary ethylbenzene (1) + octane (2) + propylbenzene (3) mixtures at 298.15 K, 308.15 K and 318.15 K.