reorganization of solvents around the radicals, the termination outside the cage, which requires larger change than that inside the cage, is highly viscosity dependent. Furthermore, while the bulk viscosity of each solvent shows good correlation with Fdif and Disp/Comb selectivity, microviscosity is the better parameter predicting Fdif and Disp(dif)/Comb(dif) selectivity regardless of the solvents.
Key Role of Ti(IV) in the Selective Radical−Radical Cross-Coupling Mediated by the Ingold-Fischer Effect
作者:Raffaele Spaccini、Nadia Pastori、Angelo Clerici、Carlo Punta、Ombretta Porta
DOI:10.1021/ja807613q
日期:2008.12.31
We report an innovative approach for the selective synthesis of polyfunctional derivatives by cross-combination of different radicals generated under mild conditions. The coordinating effect of Ti(IV) plays a key role in the reaction mechanism: due to its chelating action on the hydroxyl groups, it promotes the homolytic C-C bond cleavage of alpha,beta-dihydroxy ketones by enhancing the captodative
Emulsion Polymerization of <i>N</i>-Ethylacrylamide in Supercritical Carbon Dioxide
作者:Weijun Ye、Joseph M. DeSimone
DOI:10.1021/ma048863q
日期:2005.3.1
Herein, we report the emulsionpolymerization of a water-soluble vinylic monomer in supercriticalcarbondioxide. The water-soluble/CO2-insoluble monomer, N-ethylacrylamide, was effectively emulsified in CO2 continuous phase using an amphiphilic diblock copolymer consisting of a d-glucose-containing glycopolymer and a fluorinated block. The resulting high yield (>90%) of water-soluble poly(N-ethylacrylamide)
在此,我们报道了水溶性乙烯基单体在超临界二氧化碳中的乳液聚合。使用由含d-葡萄糖的糖聚合物和氟化嵌段组成的两亲性二嵌段共聚物,在CO 2连续相中有效地乳化了水溶性/ CO 2不溶单体N-乙基丙烯酰胺。水溶性聚N的高收率(> 90%)(-乙基丙烯酰胺)以稳定的聚合物胶体形式获得,该胶体由亚微米级的颗粒组成。粒径和粒径分布受各种反应参数的影响。较高的温度和较高的表面活性剂和引发剂浓度导致颗粒尺寸较小。使用了两种引发剂2,2'-偶氮二异丁腈(AIBN)和氟化的偶氮衍生物双-[2-(F-辛基)乙基] -4,4'-偶氮双-4-氰基戊酸酯,并对其进行热分解。研究了超临界CO 2中的行为。与AIBN引发的体系相比,由氟化偶氮引发剂引发的乳液聚合显示没有聚合的单体液滴,并且所得颗粒更均匀。
Surface photochemistry: evidence for rotational and translational movement of cyanopropyl radicals on a silica gel surface
作者:Linda J. Johnston、Paul de Mayo、S. King Wong
DOI:10.1039/c39820001106
日期:——
The photolysis of azoisobutyronitrile is shown to generate radicals which, contrary to an earlier report, undergo rotational and translational movement on a silicagelsurface.
与较早的报道相反,偶氮异丁腈的光解显示会产生自由基,该自由基在硅胶表面上经历旋转和平移运动。
Surface photochemistry: decomposition of azobis(isobutyronitrile) on dry silica gel