Kinetic evidence for a novel, Grob-like substitution/fragmentation mechanism for the reaction of nucleophiles with trialkylammoniomethyl halides
作者:Michelle O. Fletcher、Li Zhang、Quyen Vu、William R. Dolbier, Jr.
DOI:10.1039/a900218i
日期:——
bimolecular mechanism for the unusual nucleophilic substitution/fragmentation reactions of iodide ion with (halomethyl)trimethylammonium salts. The relative reactivities of allyl, ethyl and methyl groups for this Grob-like reaction are also determined. Activation parameters are presented for the thermal reactions of 1-iodo-N,N,N-trimethylmethaniminium iodide (log A = 8.7, Ea = 19.0 kcal mol–1) and
动力学证据表明,碘离子与(卤甲基)三甲基铵盐发生不寻常的亲核取代/断裂反应的是一种协同的双分子机理。还确定了该Grob-样反应的烯丙基,乙基和甲基的相对反应性。激活参数被呈现为1-碘的热反应Ñ,Ñ,Ñ -trimethylmethaniminium碘(登录甲 = 8.7,Ë一个 = 19.0千卡摩尔-1)和1-碘- Ñ -allyl- Ñ,Ñ -dimethylmethaniminium碘化物(log A = 14.6,E a在乙腈中 为25.7 kcal mol –1),后者在70°C时观察到的二级速率常数比前者大39倍。将结果与休斯,英戈尔德和科南特的烷基卤的S N 2反应的经典数据进行比较。
The Single- and Double-Strand Cleavage of DNA by a Cationic Dicobalt Complex by Visible Light
spin-trapping. Strong binding of the dicobaltcomplex with six cationic moieties toward DNA was confirmed by ethidium bromide displacement assays with K app = 3.2 x 10 7 M -1 at 298 K, the value was 100 times that of corresponding monocobalt complex with K app = 3.3 x 10 5 M -1 . The dicobaltcomplex exhibited high ability for single- and double-strand DNA cleavage in comparison with that for the corresponding
报道了一种具有双阳离子烷基作为自由基来源的新型聚阳离子有机二钴络合物的一锅法合成。通过元素分析、UV-vis、 1 HNMR、IR 和 CSI-质谱对该复合物进行表征。CSI-MS 提供完整的母离子峰,在复合物中具有不稳定的钴-碳键。该复合物是光敏的,在可见光照射下钴-碳键的光裂解产生双阳离子碳中心自由基,可通过 EPR 自旋捕获检测到。通过溴化乙锭置换试验证实了具有六个阳离子部分的二钴复合物与 DNA 的强结合,K app = 3.2 x 10 7 M -1 在 298 K,该值是相应的单钴复合物的 100 倍,K app = 3.3 x 10 5 M -1 。
A high-temperature molecular ferroelastic phase transition and switchable dielectric response in the trimethylbromomethylammonium salt [C<sub>4</sub>H<sub>11</sub>NBr] [PF<sub>6</sub>]
ordered–disordered motion turn out to be crucial in the generation of the ferroelastic phase transition. Therefore, this molecular design strategy of introducing halogens to tetraalkylammoniums can not only reduce the symmetry of the tetraalkylammonium molecules at room temperature, but can also maintain the highly disordered characteristics at high temperatures. This provides an efficient route for us to find
effective local piezoelectric coefficient of TMBM-MnBr3 films is comparable to that of its bulk crystals. In terms of ferroelectric performance, it is the low coercive voltages, combined with the multiaxial characteristic, that ensure the feasibility of piezo film applications. Based on these, along with the common superiorities of molecular ferroelectrics like light weight, flexibility, low acoustical impedance
Molecular piezoelectrics are attracting tremendous interest because of their easy processing, light weight, low acoustical impedance, and mechanical flexibility. However, reports of molecular piezoelectrics with a piezoelectric coefficient d33 comparable to piezoceramics such as barium titanate (BTO, 90-190 pC/N) have been scarce. Here, we present a uniaxial molecular ferroelectric, trimethylchloromethylammonium