Reaction of N-(2-hydroxyethyl) ethylenediamine over zeolite and chromite catalysts

N-(2-hydroxyethyl) ethylenediamine reaction was observed over zeolite catalysts giving rise to only dehydrocyclization and over chromite catalysts showing dehydrocyclization together with dehydrogenation. The major product changes from the cyclized compound piperazine to pyrazine when the reactant is switched from zeolite to chromite catalyst. This process stands as a model reaction for characterizing lone acid sites and adjacent acid-base sites over zeolite and chromite catalysts, respectively.IICT Communication No. 3175     

YPxV1—xO4（0≤x≤1）：Dy^3＋的合成及其光谱性质的研究

本文报道了不同组成的ＹＰｘＶ１－ｘＯ４（０≤ｘ≤１）：Ｄｙ＾３＋的合成和结构。ＹＰｘＶ１－ｘＯ４（０≤ｘ≤１）为四方晶系，晶胞参数随ｘ的增大呈线性减小。基质的Ｓｔｏｋｅｓ位移随ｘ的增大逐渐变大，而激发光谱峰值则向短波方向移动。在ＹＰｘＶ１－ｘＯ４：０．００６Ｄｙ＾３＋体系中，ｘ＞０．４时出现的基质发射是由ＰＯ＾３－４引起的。基质及Ｄｙ＾３＋的发光效率和Ｄｙ＾３＋的发光强度的黄蓝比均与ｘ有关。同时探     

Notes on Kuhn's ω″ molecular orbital method

(1) It is shown that, contrary to statements sometimes made, it is perfectly possible to obtain consistent sets of charges in Kuhn's ω″ molecular-orbital method, whatever the values of the parameters ω, ω′, ω″.

(2) Particular applications are made to the benzyl cation, and to the non-alternants fulvene, heptafulvene and azulene. It appears that including the ω-terms decreases the magnitude of the largest of the net atomic charges as calculated by the simple Hückel method, and results in an overall smoothing-out process. Further inclusion of the ω′-terms continues this smoothing-out process, but inclusion of the ω″-terms may sometimes slightly reverse this process.

(3) The charge distributions obtained for fulvene and azulene in (1) and (2) lead to molecular dipole moments which are still much too large.

In view of (3) it is not clear that the additional work involved in the inclusion of ω′ and ω″ is justified by the greater accuracy thus obtained.     

ZrxTixAl1-2xO2的制备及其在三效催化剂上的应用

Zr_0.5Ti_0.5O₂(ZT) and Zr_0.25Ti_0.25Al_0.5O₂(ZTA) mixed oxides were prepared by co-precipitation method and characterized by low temperature adsorption-desorption， XRD and NH₃-TPD. The activity of Pt/Zr_0.5Ti_0.5O₂ and Pt/ Zr_0.5Ti_0.5Al_0.5O₂ catalysts was evaluated using the simulated gases. The results show that ZTA samples exhibit higher specific surface area， larger pore volume and proper surface acidic amount and acidity in comparison with ZT. The results of the catalytic test indicate that Pt/ZT and Pt/ZTA catalysts exhibit excellent low-temperature catalytic activity and lower light-off temperatures of hydrocarbon， carbon monoxide and nitrogen oxides， especially better conversion for nitrogen oxides (NO_x). The addition of Al₂O₃ into ZT enhanced the anti-aging property of Pt/ ZTA catalysts due to the excellent textural， structural， surface acidity and thermal stability.     

Formation of Cyclic Oligomers in Concentrated Aqueous Solutions of Formaldehyde

An MNDO calculation gave the formation enthalpies of the components of equilibrium mixtures in concentrated aqueous acid solutions of formaldehyde. The results of this study suggest that intramolecular cyclization of linear oligomers with 5 and 9 CH₂O units, respectively, is the most plausible mechanism of formation of cyclic oligomers of formaldehyde — trioxane and tetraoxane. Ring protonation by the hydroxonium ion with ring opening is the most energetically favorable route of cyclic acetal decomposition.     

L-asparaginase bound in a polyacrylamide gel

Summary The enzyme L-asparaginase fromE. coli has been included in polyacrylamide gel, and some of its properties have been investigated: stability, pH dependence, heat stability, K_m. It has been shown that the enzymegel obtained has a better stability then the native enzyme.Institute of Organic Synthesis, Academy of Sciences of the Latvian SSR, Riga. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 382–384, May–June, 1976.     

Furocoumarins ofCnidium dubium

Summary 1. Paper chromatography has shown that the fruit ofC. dubium contains not less than eight substances of coumarinic nature; six of these (A, B, C, D, E, and H) have been isolated in the crystalline state.2. Substances B, D, and E are identical with isoimperatorin, imperatorin, and oxypeucedanin, respectively. Some properties of substance H have been determined. Prangenin [F] has been detected in the fruit ofC. dubium by paper chromatography.3. The structure of two new compounds has been established: substance A (cnidicin) (I) is 5, 8-di-(, -dimethylallyloxy) psoralen, and substance C (cnidilin) (II) is 5-(, -dimethylallyloxy)-8-methoxypsoralen.Khimiya Prirodnykh Soedinenii, Vol. 2, No. 6, pp. 375–380, 1966     

化学计量学研究及其应用

本文介绍了化学计量学的产生、发展、研究内容及主要应用,对有关工作进行了评述。     

Photoacoustic spectroscopy of solids and surfaces

After briefly reviewing the theory and instrumentation, results from a variety of experiments carried out by the authors on the photoacoustic spectroscopy of solids and surfaces by employing an indigenous spectrometer are discussed in the light of the recent literature. Some of the important findings discussed are, phase angle spectroscopy, anomalous behaviour of monolayers, unusual frequency dependence in small cell volumes, spectra of a variety of solids including amorphous arsenic chalcogenides, photoacoustic detection of phase transitions and determination of surface areas and surface acidities of oxides. Recent developments such as piezoelectric photoacoustic spectroscopy, depth profiling and subsurface imaging are also presented. Contribution No. 124 from the Solid State and Structural Chemistry Unit.     

Structure and Vibrational Spectra of 1:1 Chloranilic Acid (CLA)—Tetramethylpyrazine (TMP) Complex

In searching for new molecular materials the crystals of 1:1 complexes of tetramethylpyrazine (TMP) with chloranilic acid (CLA) were grown. In the crystalline lattice of TMP.CLA infinite chains of hydrogen bonded components are formed. Very strong (d_(O·sN) = 2.692(2) {?}) hydrogen bonds without proton transfer are present. The components of the complex form stacks of parallel arrangement with the distance typical of van der Waals interaction. One can conclude that in packing, interactions via hydrogen bonds play a decisive role. In the IR spectrum one observes a broad, continuous absorption with well resolved trio typical of strong hydrogen bonds. A detailed analysis of IR and Raman spectra in the low frequency region related to deformation vibrations of CH₃ groups shows that strong interaction via hydrogen bonding only slightly affects the dynamics of these groups.