Effect of subsurface oxygen on the reactivity of the Ag(111) surface

Periodic, self-consistent, density functional theory calculations have been performed to demonstrate that subsurface oxygen (O(sb)) dramatically increases the reactivity of the Ag(111) surface. O(sb) greatly facilitates the dissociation of H2, O2, and NO and enhances the binding of H, C, N, O, O2, CO, NO, C2H2, and C2H4 on the Ag(111) surface. This effect originates from an O(sb)-induced upshift of the d-band center of the Ag surface and becomes more pronounced at higher O(sb) coverage. Our findings point to the important role that near-surface impurities, such as O(sb), can play in determining the thermochemistry and kinetics of elementary steps catalyzed by transition metal surfaces.     

A Rapid and Convenient Synthesis of Derivatives of Imidazoles under Microwave Irradiation

An efficient and a quick microwave‐assisted synthesis of benzimidazoles and trisubstituted imidazoles was developed. Three benzimidazoles were obtained as a result of the condensation of 1,2‐phenylenediamine with carboxylic acids and acetoacetic ester without catalyst. A series of trisubstituted imidazoles were synthesized by condensation of benzil, aromatic aldehyde and ammonium acetate in the presence of glacial acetic acid.     

Coriatone and corianlactone, two novel sesquiterpenes from Coriaria nepalensis

Both coriatone (1). a novel highly oxygenated picrotoxane-type sesquiterpene, and corianlactone (2). with an unprecedented sesquiterpene basic skeleton, named coriane, were isolated from Coriaria nepalensis Wall. The structures of 1 and 2 were determined by analysis of their two-dimensional NMR data, and the structure of 2 was confirmed by X-ray analysis. Compounds 1 and 2 showed no remarkable inhibitory activity toward K(562) cells. They are cytotoxic with IC(50) > 50 microg/mL (cis-platinim: IC(50) = 0.49 microg/mL).     

Reinvestigation of CS2 dissociation at 193 nm by means of product state-selective vacuum ultraviolet laser ionization and velocity imaging

A branching ratio of 1.6 +/- 0.3 for S(3P)/S(1D) is obtained for the dissociation of CS2 with very low fluence 193 nm laser (less than 2 mJ/cm2), in which the S(3P) and S(1D) have been state-selectively ionized using VUV lasers at different wavelengths. The anisotropy parameters betamax(3P) = 0.8 and betamax(1D) = 1.9 indicate that these channels are preferentially populated at different geometries and the lifetime is very short.     

The photochemical and thermal reactions of a triosmium cluster carrying a γ-pyrone ligand with alkynes

The reaction of the cluster Os₃(CO)₁₀(μ-H)(μ-γ-C₅H₃O₂) (1) with a number of alkynes under thermal or visible light irradiation conditions, afforded in most cases the dinuclear complexes Os₂(CO)₆(μ-γ-C₅H₃O₂)(μ-LH) (L=PhCCPh, ^tBuCCH, ^tBuCCMe or EtCCEt) (2) or the trinuclear chain complexes Os₃(CO)₉(μ-H)(μ-γ-C₅H₃O₂)(μ-RCCHC₆H₄) (R=H, Ph) (3). In the case of PhCCPh, a new isomer of Os₃(CO)₈(PhCCPh)₂, viz., Os₃(CO)₈(μ-PhCCPh)(μ-PhCCHC₆H₄) (7) has been isolated and characterised.     

几种新的聚合物冠醚的合成及其络合与催化性能

由一、二、三和四缩乙二醇双钠盐与带有活泼卤原子的聚β-氯乙基缩水甘油醚进行环化反应,制备了四种新的聚合物冠醚(Ⅰ、Ⅱ、Ⅲ、Ⅳ)。络合容量测定结果表明,它们对K~+、Na~+均有较好的络合能力。在催化Wolff-Kishner(二苯甲酮腙还原为二苯甲烷)和正溴辛烷的碘代反应中,它们是有效的相转移催化剂。其中以Ⅱ最好,它的催化活性与小分子冠醚18-C-16和DB18-C-6相似,且易于回收,重复使用。     

Pt/HL和Pt/KL沸石在异丙醇分解反应中的不同催化行为

Ｐｔ／ＫＬ沸石在异丙醇分解反应中具有很高的脱氢活性,而Ｐｔ／ＨＬ沸石具有明显的缺电子性,在此反应中难以显示出脱氢活性,通过加氢作用,可使沸石的酸位免受积炭覆盖,从而可增强Ｐｔ／ＨＬ沸石的酸性催化作用。     

便携式微波等离子体离子化检测器气相色谱仪用于气体分析的研究

本文使用自制的便携式微波诱导等离子体离子化检测器气相色谱仪对可燃气体中N_2、O_2、H_2和CH_4的测定方法进行了研究。以氩气为载气和工作气体,考察了改进后的微波诱导等离子体离子化检洲器(MIPID)的工作参数对测定的影响。对煤气和乙炔中的O_2、N_2、H_2和CH_4进行了测定,分析结果与热导池检测器(TCD)的气相色谱法一致。讨论了高电离电位(>11.7ev)气体组分在MIPID中响应特性。     

Zn—TppS4极谱络合物吸附波的研究：中草药天麻,川芎,当归中锌的测定

锌是人体必需的微量元素之一。它具有重要的生理功能和营养作用,是合成脱氧核糖核酸(DNA),核糖核酸(RNA)和蛋白质必需的金属离子。锌是DNA,RNA聚合酶等80多种酶的组成成分及激剂,直接影响细胞代谢,免疫过程,细胞分裂和再生。最近美国有人提出缺     

7种中位—四取代苯基卟啉化合物的合成

卟啉是一类结构与生命物质(如血红素和维生素B_(12))相似的化合物,近年来曾被用于人体肿瘤的光动力学治疗;此外,在电化学、光物理学和光化学、放射医学、微量元素测定、纺织品漂洗等领域中的应用也相当广泛,已受到科技工作者的普遍关注和重视。本文按Rothemond法将相应的取代苯甲醛与新蒸吡咯在丙酸中缩合,制得具有酸性、中性和碱