Thermal stability of brominated poly(isobutylene‐co‐isoprene)

The thermal stability of brominated isobutylene–isoprene rubber (BIIR) was investigated through studies of the elastomer and a model compound that accurately represented the reactive functionality within the polymer. An analysis of commercial BIIR and reaction products of brominated 2,2,4,8,8‐pentamethyl‐4‐nonene (BPMN) by NMR demonstrated that bromination of isobutylene–isoprene rubber by 1,3‐dibromo‐5,5‐dimethylhydantoin yielded a kinetically favored exomethylene substitution product, 3‐bromo‐6,6‐dimethyl‐2‐(2,2‐dimethylpropyl)‐1‐heptene ( 2 ), as opposed to the more stable endo‐isomer, (E,Z)‐4‐(bromomethyl)‐2,2,8,8‐tetramethyl‐4‐nonene ( 3 ). The exposure of BIIR and the brominated model compound BPMN to vulcanization temperatures led to the isomerization of 2 to 3 at a rate strongly dependent on HBr concentration. The elimination of HBr from these allylic bromides to produce exo‐ and endo‐conjugated dienes proceeded concurrently with isomerization, and the kinetics of these processes could be rationalized on the basis of a polar reaction mechanism. The product distributions obtained from both the model system and BIIR were consistent, thereby justifying an extension of the model compound approach to an analysis of BIIR vulcanization chemistry. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2019–2026, 2001     

环氧树脂与氰酸酯共固化产物性能的研究

环氧树脂是一类综合性能优良并获广泛应用的热固性树脂基体 .但是通常的环氧树脂基体中含有大量反应生成的羟基等极性基团 ,吸湿率高 ,使其复合材料在湿热环境下力学性能和介电性能显著下降 .应用氰酸酯改性固化的环氧树脂等热固性树脂 ,将赋予以其为基体的复合材料以优异的耐热性能、力学性能和介电性能[1 ,2 ] .这类复合材料的研究开发对特种电子电气绝缘材料和先进复合材料的发展具有重要意义 .作者曾应用ＦＴ ＩＲ、ＤＳＣ等分析技术对氰酸酯与环氧树脂 (氰酸酯在欠量、适量和过量条件下 )的共固化反应机理和固化物结构特征等进行过深入…     

Al_(66)Mn_9Ti_(25) La金属间化合物的变形行为与机制

研究了微量稀土元素La对Al6 6 Mn9Ti2 5 金属间化合物显微组织、变形行为、裂纹生成的影响。在Al6 6 Mn9Ti2 5 金属间化合物中添加微量La ,保持L12 结构 ,晶格常数基本无变化 ,促进了晶粒枝晶化和第二相弥散化 ,起到一定的抑制微裂纹生成和扩展以及沿晶开裂的作用 ;同时 ,还可增强位错的可动性 ,使压缩塑性得到改善。探讨了La改善变形行为的机制。     

激光促进甲醇在杂多化合物上的表面反应

利用红外光谱 (IR)、程序升温脱附 (TPD)和激光促进表面反应 (L SSR)技术 ,研究了甲醇吸附于杂多化合物 H3PMo1 2 O40 · x H2 O、H3PW1 2 O40 · x H2 O、H6 PMo6 W6 O40 · x H2 O表面上所形成体系的振动结构、化学吸附形态和光促表面反应规律 .实验结果表明 ,在各固体材料表面上甲醇同时发生分子吸附和解离吸附 ,且在室温条件下体系即发生显著的光促表面反应 ;与甲醇吸附强度和吸附量相比 ,反应体系的振动结构对 L SSR效率起着更重要的作用 .根据表征和反应结果 ,分析了体系中活性物种的产生途径 ,并给出了反应机理的模型     

钒化合物对酸性镀锡溶液的稳定作用

研究了钒化合物稳定剂对酸性SnSO4 溶液稳定性的影响 .可见光谱分析表明稳定剂中主要含有VO2 + 和少量的V3+ ,循环伏安实验显示在 - 0 .2 0～ - 0 .55V(vs .SCE)电位范围内VO2 + 能够在阴极上还原为V3+ ,在更负的电位下V3+ 能进一步还原到V2 + .实验结果说明稳定剂中的低价钒离子有效地清除了镀液中的溶解氧 ,因而防止了Sn2 + 离子的氧化 ,显著地提高了酸性锡镀液的稳定性 .     

Theoretical study of the internal rotational barriers in nitrobenzene, 2‐nitrotoluene, 2‐nitrophenol,and 2‐nitroaniline

The molecular geometries and internal rotational barriers of the nitro group of nitrobenzene (NB), 2‐nitrotoluene (2‐NT), 2‐nitroaniline (2‐NA), and 2‐nitrophenol (2‐NP) were calculated by five different types of density functional theory (DFT) methods with three different levels of basis sets. Analysis of the torsional angles of the nitro, methyl, amino, and hydroxyl groups indicate that NB, 2‐NA, and 2‐NP are planar molecules, but 2‐NT is not a planar molecule. Internal rotational barriers of the nitro group were calculated as V₂ barriers, and the NO₂ torsional potentials for each molecule were given. The values of the V₂ barriers depend on the DFT methods and basis sets. The average values of the V₂ barriers for NB, 2‐NT, 2‐NA, and 2‐NP are 6.47 kcal/mol, 3.00 kcal/mol, 10.20 kcal/mol, and 13.26 kcal/mol, respectively. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 83: 332–337, 2001     

沸石表面有机金属化学ZSM-5外表面上——Ge(n-C4H9)x基团的接枝及其性质研究

用气体分析及IR,NMR和元素分析等方法研究了真空系统中230℃和280℃下四丁基锗在ZSM-5沸石表面上的接枝反应,并对所得沸石的热稳定性和吸附性质进行了表征,与作者曾报道的硅胶及丝光沸石上的反应类似,四丁基锗也能与ZSM-5沸石表面上的硅羟基发生缩合反应,在其外表面或孔口生成组成为(=Si-O)xGe(n-C4H9)4-x(x=2~3)的表面有机锗化合物,在２３０℃接枝丁基锗基团不影响沸石的结构和表面积,仅改变它的孔口大小,在改性后的沸石上,Ｎ２的吸附性质没有改变,而不同分子尺寸的烃,加正已烷,２-甲基戊烷,２,３-二甲基丁烷却呈现出完全不同于起始ＺＳＭ-５沸石的择形吸附效应.     

用色谱-质谱方法鉴定薄荷油中的异构体

用毛细管气相色谱－质谱联用、程序升温方法分析了一种薄荷油的化学成分、共分离出20个组分,其中含4组异构体,它们分别是：m/z=136的5个成分α－蒎烯、β－蒎烯、β－月桂烯、α－菲兰烯和柠檬烯;m/z＝154的2个成分（cis)－薄荷酮和（2R－cis)－薄荷酮;m/z＝156的2个成分（1α.2α.5β）－薄荷醇和（1α.2β.5β）－薄荷醇;以及m/z＝204的8个成分（1α,3aα,3bβ,6aβ,6bα）－十氢－3a－甲基－6－亚甲基－1－异丙基－环丁烷并[1,2:3,4]二环戊烯、[1R-(1R,4E,9S)－4,11,11－三甲基－8亚甲基－双环（7．2．0）十一碳4－烯、[1R-(1aα,7α,7aα,7bα]-1a,2,3,5,6,7,7a,7b-八氢－1,1,7,7a-四甲基－1氢－环丙烷[α]并萘、[1aR-(1aα,4aα,7α,7aβ,7bα）－十氢,1,1,7－三甲基4－亚甲基－1－氢－环丙烷[e]并奥、（1S-exo）－2－甲基－3－亚甲基－2－（4－甲基－3－戊烯基）－二环（2．2．1）庚烷、（3aα,3bα,4α,7β,7aR）－八氢－7甲基－3亚甲基－4－异丙基－1氢－不戊烷[ 1,3]并环丙烷[1,2]并苯、1－乙烯基－1－甲基－2－异丙烯基－4（1－甲基亚乙基）环己烷和绿叶烯。     

Synthesis and Structure of Dimolybdenum(I) Carbonyl Compound with Thiolate and Carboxylate Mixed-tri-bridging Ligands [Bu_4N][Mo_2(CO)_6(SC_6H_4Cl-p)_2(CF_3COO)]

1 INTRODUCTION Molybdenum(I) compounds, in particular Mo(I)-SR compounds, are rare amongst numerous Mo compounds. So far, only the following compounds [Mo2(CO)8-n(SR)2(CH_3CN)n] (R = C6H5, CH_2CO2Et, n = 0, 2)[1～5] have been reported in the literature. Recently, we make an effort to develop investigations on Mo(I) compounds on the basis of preparing new Mo(I) compounds by introducing different functional ligands into Mo2(SR)2(CO)8, then determining their structures and measur…     

Synthesis and structural characterization of a novel dimolybdenum(I) compound with mixed‐tribridging ligands: [Bu4N][Mo2(μ‐SPh)2(μ‐Cl(CO6]

A novel mixed‐tribridged dimolybdenum(I) compound [Bn₄N][Mo₂(μ‐SPh)₂(μ‐Cl)(CO)₆] (1) has been synthesized from the reaction of Mo₂(CO)₃(SPh)₂ with BU₄NCl. Compound 1 was characterized by IR, UV‐Vis and ¹H, ¹³C, ⁹⁵Mo NMR spectroscopic analyses. The electrochemical behavior was measured by cyclic voltammetry, indicating a quasi‐reversible two‐electron transfer in one step. The crystal structure determined by X‐ray crystallography shows that 1 contains a [Mo₂(μ‐S)₂(μ‐Cl)]^? core with a planar Mo₂S₂unit and a Cl bridge. The Mo? Mo distance is 0.28709(7) nm, and the Mo‐Cl‐Mo angle is 66.44(4)°. A newface‐sharing bioctahedral structure is discussed.