Molecular motions in poly(diethyl siloxane) studied by solid-state29Si NMR

Molecular motions in poly(diethyl siloxane) were studied by solid-state²⁹Si-NMR in the temperature range 180–350 K. In this temperature range two solid phases ₁ and ₂, a mesophase _m, and an amorphous isotropic phase exist. The nature of the chain mobility in the different phases was deduced from the resulting changes in the NMR line-shape governed by anisotropic chemical shift. In the intermediate solid phase ₂ its anisotropy is reduced by 25% compared with the low temperature phase ₁ due to the onset of oscillations around the chain axis and conformational transitions. In the mesophase _m the polymer chain rotates about its long axis yielding an axially symmetric chemical shift tensor opposite in sign to that in the ₁, ₂ phases. The broad transition of the mesophase into the isotropic phase is accompanied by an increase in a narrow Lorentzian line arising from the amorphous phase. The results are compared with previous¹H NMR, Raman-spectroscopy and x-ray measurements.After completion of this work we learnt that PDES has recently also been studied through¹³C-MAS and²⁹Si-NMR by Möller et al. [13].     

Synthesis of functionalized heterocycles by alkylation of β-dicarbonyl compounds with 2,3-dibromopropan-1-ol

Alkylation of β-dicarbonyl compounds with 2,3-dibromopropan-1-ol in the K₂CO₃-dibenzo-18-crown-6 system in toluene leads to products of C,O- or C,C-cycloalkylation. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1695–1697, September, 1997.     

二茂铁基-1,1’-二烷基二茂铁甲醇的合成与性质

10种二茂铁甲酰基 -1 ,1 -二烷基二茂铁经 Li Al H4还原得到 1 0种相应的二茂铁基 -1 ,1 -二烷基二茂铁甲醇 .这类羟基化合物对酸的敏感性很高 .由 2种二茂铁基 -1 ,1 -二乙基二茂铁甲醇与 BF3在二氯甲烷中反应形成了稳定的二茂铁基 -1 ,1 -二乙基二茂铁甲基碳正离子 .无需从反应混合物中分离 ,该离子与乙胺作用得到了 2种 N-取代产物 .由元素分析、红外光谱和核磁共振氢谱证实了化合物的结构     

Initiation reactivity of anionic polymerization of fluorinated acrylates and methacrylates with diethyl(ethyl cyanoacetato)aluminum

Pseudo first‐order rate constants of the reaction of diethyl(ethyl cyanoacetato)aluminum [(C₂H₅)₂Al(NCCHCOOC₂H₅)] with 17 fluorinated acrylates and methacrylates and five hydrocarbon analogs for references were investigated to examine the initiation reactivities of the anionic polymerization of fluorinated vinyl monomers to afford the reactivity order: CH₂?C(CF₃)COOC₂H₅ > CH₂?C(CF₃)COOCH(CH₃)₂ > CH₂?CHCOOCH₂C₆F₅ > CH₂?C(CF₃)COOC(CH₃)₃ > CH₂?C(CF₃)COOCH₂C₆F₅ > CH₂?C(CF₃)COOCH(CF₃)₂ ≥ CH₂?CHCOOCH₃ > CH₂?CHCOOCH₂C₆H₅ ≥ CH₂?C(CF₃)COOCH₂CF₃ > CH₂?C(CH₃)COOCH₂C₆F₅ > CH₂?CHCOOCH₂CF₃ > CH₂?CHCOOCH₂C₂F₅ > CH₂?CHCOOCH(CF₃)₂ > CH₂?C(CH₃)COOCH₃ > CH₂?C(CH₃)COOCH₂C₆H₅ ≥ CH₂?C(CH₃)COOCH₂CH₂C₈F₁₇ > CH₂?C(CH₃)COOCH(CH₃)₂ > CH₂?C(CH₃)COOCH₂C₂F₅ ≥ CH₂?C(CH₃)COOCH₂CF₃. No rate constants for CH₂?C(CH₃)COOCH(CF₃)₂, CH₂?CFCOOC(CH₃)₃, and CH₂?CFCOOCH₂C₂F₅ were obtained because of too fast polymerization. The incorporation of a trifluoromethyl group into the vinyl group enhanced the reactivity toward the delocalized carbanion. The reactivity of other fluorinated acrylates and methacrylates was concluded to approximately be controlled by the fluorine contents and the bulkiness of substituents of monomers. The reactivity was generally decreased by increasing fluorine contents of fluoroalkyl substituents in ester groups. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7011–7021, 2008     

Lewis acid-catalyzed reactions of N′-(2-alkynylbenzylidene)hydrazides with diethyl phosphite

Lewis acid catalyst-tuned reactions of N′-(2-alkynylbenzylidene)hydrazides with diethyl phosphite are described. Isoquinolin-1-ylphosphonate is generated when copper triflate is utilized as catalyst, while 2-amino-1,2-dihydroisoquinolin-1-ylphosphonate is obtained in the presence of palladium acetate.     

Ionic liquids as novel and recyclable reaction media for N-alkylation of amino-9,10-anthraquinones by trialkyl phosphites

Ionic liquids such as 1,3-dialkylimidazolium bromides make excellent catalysts and solvents for N-alkylation of amino-9,10-anthraquinones in the presence of trialkyl phosphites. For triethyl phosphite, [bpim][Br] gave better results. The ionic liquids are successfully regenerated and reused.     

New 3D Framework Vanadium（Ⅲ） Phosphite with One-dimensional 4,12-Member Ring Channels

A new vanadium(Ⅲ) phosphite,V2(HPO3)3(1),was synthesized hydrothermally with V2O5,H3PO3 as reactants,1,6-diaminopropane(1,6-HAD) as the structure-directing agent and characterized by single crystal X-ray diffraction,powder X-ray diffraction,IR spectroscopy,TGA,ICP-AES and elemental analyses.Single-crystal X-ray diffraction analysis reveals that compound 1 crystallized in the P6(3)/m hexagonal space group with the unit-cell parameters:a=0.80436(10) nm,c=0.73972(2) nm,V=0.41447(13) nm3,Z=4.The construction of...     

无溶剂合成酰基二茂铁的新方法

以二茂铁为原料,乙酸酐、丙酸酐、丁酸酐和苯甲酸酐为酰化剂,45%~47%三氟化硼乙醚溶液为催化剂,无溶剂合成了4种酰基二茂铁,总产率81%~92%,其结构经¹H NMR和¹³C NMR确证。