酸、碱性条件下茜素红紫外-可见光谱的量子化学研究

茜素红(ARS)是葸醌类化合物中茜草素型的一种,被广泛应用于电化学、光谱学等领域的研究。在酸性溶液中,茜素红主要在260 nm和422 nm处出现明显的吸收峰,而在碱性溶液中吸收峰移动到272 nm和556 nm。为了分析不同溶液环境对茜素红吸收峰波长的影响,本研究在杂化密度泛函方法B3LYP/6-311+(d)水平上优化了ARS分子在酸、碱性情况时的稳定基态构型,并采用含时密度泛函(time-dependent density functional theory,TD-DFT)方法模拟了ARS分子的电子吸收光谱。计算结果与实验得到的紫外可见吸收光谱相吻合,说明密度泛函理论用来研究茜素红的紫外可见光谱是有效可靠的。通过计算还确定了每个吸收峰对应的各个电子跃迁的贡献率以及Mulliken电荷分布。该理论与实验的结合研究为茜草素型化合物的进一步应用、分子设计、药物构效关系和化学反应规律的研究提供了重要的参考依据。     

Cysteine adds to lipid hydroperoxide

Cysteine reacts with linoleic acid hydroperoxide to yield several products, some of which were identified as fatty acid-cysteine adducts. The addition was catalyzed by ferric chloride (10⁻⁵ M) by initiating free radical reactions. When isomerically pure 13-hydroperoxy-cis-9,trans-11-octadecadienoic acid and cysteine were reacted in 80% ethanol under N₂, the major adducts were 9-S-cysteine-13-hydroxy-10-ethoxy-trans-11-octadecenoic acid (I) and 9-S-cysteine-10,13-dihydroxy-trans-11-octadecenoic acid (II). When the reaction included both isomers of the hydroperoxide (13-and 9-hydroperoxide) and air, an adduct of 9-oxononanoic acid and cysteine also was isolated. Additional experiments gave information about possible mechanisms of I and II formation.     

Fabrication of Reaction-Sintered Sialon

A factorial design experiment was conducted to determine the major parameters affecting the densification of mixtures having the composition (in mol%) 50 Si₃N₄, 25 A1₂O₃, and 25 A1N. Improved densities of the resulting sialon were achieved using a longer milling time and SN-502 Si₃N₄ powder. However, sialon samples prepared from the SN-502 powder contained some of the X-phase, whereas those fabricated from AME Si₃N₄ powder did not. This difference is considered to be due to the higher SiO₂ content of the SN-502 powder and its greater susceptibility to partial hydrolysis during the milling process. Reaction-sintered sialon (97.2% theoretical density) fabricated using AME powder had a room-temperature bend strength of 352
MN/m² (51,000 psi) and exhibited slow crack growth at 1300° and 1400°C. It is suggested that this is not an inherent property of sialon but is due to the presence of a calcium-containing grain-boundary phase, as in hot-pressed Si₃N₄.     

Inclined hot-wire response equations for a flow field having a dominant tangential velocity component

Modified sets of response equations have been derived for a single inclined hot-wire probe introduced in various orientations in a flow field having a dominant tangential velocity component. By means of these equations, the components of the three dimensional mean velocity vectors, the turbulence intensity and the Reynolds stresses can be easily determined at any location in a swirling flow which is stationary with time. This method is particularly applicable to the characterization of the flow field in chemical processing equipment where this type of swirling flow is increasingly being used. It has been successfully applied to a study of the flow field in a spray-drying chamber, in the course of which good reproducibility and consistency of results were obtained.     

Predicting N mineralized in a Georgia Coastal Plain field

The N mineralized from soil organic matter provides an important portion of N available for crop production. The objective of this study was to determine the amount of spatial variability in N mineralization potential in a field and to evaluate three different methods that might be used to estimate this variability. The three methods tested included predicting the N mineralized from surface soil properties as well as from a biological and a chemical procedure. Three soils varying in N mineralization potential were selected for the study from a field in the Georgia Coastal Plain. The N mineralized from these soils was determined by an N balance of unfertilized and cropped plots. The amount of N mineralized could not be reliably predicted from surface soil organic C, although surface soil clay concentration was positively correlated with the N mineralized. The N mineralized that was predicted using mineralization parameters determined by aerobic incubation, adjusted daily for soil water content and temperature, was approximately 50% of the field measurements of N mineralized. The values of NH₄-N extracted with hot 2 M KCl were related significantly to N mineralized in the field (r²= 0.60) and also to the zero order rate constant of mineralization, k₀ (r²= 0.77), determined from the N mineralized in the aerobic laboratory incubation.     

The separation of solid fatty acids from liquid fatty acids by the formation of acid soaps. I. Tallow soaps

The formation of acid soaps has been used successfully for the separation of a mixture of fatty acids into high and low iodine value fractions. The acid soaps of saturated acid can be made to crystallize from water leaving their unsaturated counter parts in solution. Acid soaps of saturated fatty acids are well characterized compounds with the formula R-COOM.R-COOH, where R is a straight alkyl chain, and M is sodium, potassium or ammonium. Optimum crystallization conditions involve a soap concentration of 2–5%, pH adjustment to between 7.0 and 8.0, an initial crystallization temperature not below 25C, and a crystallization period of at least 4 hr during which time cooling to a final temperature of 5–10C must be gradual, and agitation gentle.     

Pressure reaction of maleic esters with vegetable oils

The reaction of dimethyl maleate and some related dienophiles with vegetable oils under pressure has been studied successfully. When safflower oil reacts with 100% excess maleate, sulfur dioxide catalyst, and hydroquinone inhibitor at 290° for 1hr., 80 to 90% yields of adduct fraction, based on linoleate, are obtained. Under the same conditions almost equally good yields result with either linseed or soybean oils. With safflower oil, dimethyl fumarate gave slightly lower yields. Di-n-butyl maleate gave even poorer yields, and much residue was formed. Paper II in a series entitled, “Reactions of Dienophiles with Vegetable Oils”. Presented at annual meeting, American Oil Chemists' Society, St. Louis, Mo., May 1–3, 1961. This is a laboratory of the Northern Utilization Research and Development Division, Agricultural Research Service, U.S. Department of Agriculture.     

Studies in Lithium Oxide Systems: XI, Li2O–B2O3–P2O5

The glassforming region in the system was roughly outlined and liquidus data were obtained for the three joins LiPO₃-BPO₄, Li₄P₂O₇-BPO₄, and Li₃PO₄-Li₂B₄O₇. Compatibility relations for the ternary subsystems Li₄P₂O₇-BPO₄-P₂O₅ and Li₂O-Li₃PO₄-Li₂B₈O₁₃ were established. Two ternary compounds with the probable compositions 22Li₂O - 11B₂O₃ - 13P₂O₅ and 2Li₂O 3B₂O₃ P₂O₅ were detected.