Pyromellitate-bridged cyclodextrin nanosponges (CDNSs) evolved from sol into gel state upon gradual increase of the concentration from 0.2 to 2000 mg mL(-1) in water. The enantiodifferentiating geometrical photoisomerizations of (Z)-cyclooctene and (Z,Z)-1,3-cyclooctadiene sensitized by CDNS at various concentrations were critically affected by the phase transition of CDNS to afford the corresponding
Cyclobutene photochemistry. Nonstereospecific photochemical ring opening of simple cyclobutenes
作者:K. Brady Clark、William J. Leigh
DOI:10.1021/ja00254a030
日期:1987.9
The photochemistry of bicyclo(3.2.0)hept-6-ene, bicyclo(4.2.0)oct-7-ene, and cis- and trans-3,4-dimethylcyclobutene has been investigated in hydrocarbon solution with monochromatic far-ultraviolet (185 and 193 nm) light sources. All of these simple cyclobutene derivatives undergo ring opening to yield the isomeric 1,3-dienes, and the latter three open nonstereospecifically to yield mixtures of the
研究了双环(3.2.0)庚-6-烯、双环(4.2.0)辛-7-烯和顺式和反式-3,4-二甲基环丁烯在具有单色远紫外光的烃溶液中的光化学( 185 和 193 nm) 光源。所有这些简单的环丁烯衍生物都进行开环以产生异构的 1,3-二烯,后三种以非立体有择的方式打开以产生可能的几何异构体的混合物。异构的 3,4-二甲基环丁烯产生三种 2,4-己二烯异构体的不同混合物,并且在每种情况下,混合物被加权以有利于轨道对称性禁止异构体。已尝试在纯反旋转的背景下分析双环 (4.2.0) 辛烯和异构 3,4-二甲基环丁烯开环的相对异构二烯产率,最近的 ab initio 计算表明的绝热开环机制应该是可能的。虽然前一种化合物的结果与这种机制一致,但对后两种化合物光解产生的异构 2,4-己二烯的相对产率的分析表明,通过正式禁止的旋转途径进行的光化学开环可能在一定程度上竞争具有旋转环开口。
Cyclobutene photochemistry. Identification of the excited states responsible for the ring-opening and cycloreversion reactions of alkylcyclobutenes
作者:W. J. Leigh、K. Zheng、N. Nguyen、N. H. Werstiuk、J. Ma
DOI:10.1021/ja00013a039
日期:1991.6
the two compounds as well as for the parent hydrocarbon bicyclo [4.2.0]oct-7-ene. The gas-phase spectra suggest that the π,R(3s) state is the lowest energy state in bicyclo[4.2.0]octene and the 7-methyl derivative but is raised to higher energies than the π,π* state in the 7-trifluoromethyl derivative. Direct photolysis of the three compounds in hydrocarbon solution with monochromatic far-UV (193 and
In sharp contrast to the wavelength-dependent photobehaviour of simple mono-alkenes, the photochemistry of conjugated dienes was found to be independent of excitation wavelength in the region 185–254nm.
Thermal E- to Z-isomerisation of E,Z-cyclo-octa-1,3-diene
作者:Janice Bramham、Christopher J. Samuel
DOI:10.1039/c39890000029
日期:——
Deuterium labelling has shown that the isomerisation of E,Z-cyclo-octadiene to the Z,Z-isomer does not occur by a 1,5-hydrogen shift as previously supposed, and thus must occur by a trans-cis rotation.