排序方式: 共有20条查询结果,搜索用时 203 毫秒
11.
本文以2,3,5,6-四甲基亚硝基苯(ND)和苯亚甲基叔丁基氮氧化物(PBN)作自由基捕捉剂研究了甲苯基重氮盐及共冠醚络合物光解的自由基历程。ESR结果表明光解可产生相应的甲苯基自由基,并能被ND或PBN所捕获。由共ESR谱可得到甲基取代苯环上的甲基质子通过超共轭作用产生的超精细裂分,共裂分值与苯环上相同位置质子与未偶电子间极化偶合作用引起的裂分值相近。即:α_(p-)~H≈α_(P-)~(CH):α_(o-)~H≈α_(o-)~(CH)3;α_(m-)~H≈α_(m-)~(CH)3.同时还存在下列关系式:α_(p-)~H≈α_(o-)~H>α_(m-)~H. 相似文献
12.
13.
14.
15.
16.
17.
本文报道一系列取代苯基重氮盐及其18-冠-6,二苯并-24-冠-8分子络合物的1H和13C NMR,考察它们在络合前后的化学位移变化,推测这类络合物的结构和络合成键状况。 相似文献
18.
19.
Solvent effect on the conformations of α,ω-bis(4-nitrophenoxy)-alkanes with different chain lengths(N_n) was studied by UV spectra. In poor solvents such as EG-H_2O and THF-H_2O, with the increase of water content, the K-bands of N_4, N_5, N_6 and N_(10) in the UV absorption spectra shifted to longer wavelengths as compared with 4-nitrophenoxyethane(N_0). It is suggested that in poor solvents the two aromatic groups are close in parallel to each other, forming ground state complexes. The K-band of N_4 showed a blue shift from that of N_0 when the water content was around 5% this may probably be attributable to a conformation with the nitro group of one benzene ring siting on the plane of the other benzene ring. 相似文献
20.