67844-27-3Relevant articles and documents
The 2-norbornyl cation via the fragmentations of exo- and endo-2-norbornyloxychlorocarbenes: Distinction without much difference
Moss,Zheng,Sauers,Toscano
, p. 8109 - 8116 (2007/10/03)
exo- and endo-2-norbornyloxychlorocarbenes (7) were generated photochemically from the corresponding diazirines (6). Both carbenes fragmented to [2-norbornyl cation (carbon monoxide) chloride] ion pairs in MeCN or 1,2-dichloroethane solutions. Products included exo-norbornyl chloride (8), endo-norbornyl chloride (9), norbornene (10), and nortricyclene (11). Fragmentation activation energies were very low (5 s-1 in MeCN). Due to chloride return within the ion pairs, product distributions from exo- and endo-7 differed, with more endo-chloride formed from the endo-carbene: the 8/9 product ratio in MeCN was ～41 from exo-7, but only 4.6 from endo-7. Norbornene, formed by proton transfer to Cl- within the ion pairs, was a major product in both cases (44% from exo-7 and 62% from endo-7). In MeOH/MeCN, up to 28% of exo-2-norbornyl methyl ether formed at the expense of some of the norbornene, but even in 100% MeOH, the norbornyl chloride products of ion pair return still accounted for 46% and 31% of the exo-7 and endo-7 product mixtures (accompanied by 26-32% of norbornene). Electronic structure calculations on the ground states and fragmentation transition states of exo-7 and endo-7 are presented.
Photochemistry of alkyl halides. 12. Bromides vs Iodides
Kopp, Paul J.,Adkins, Rick L.
, p. 2709 - 2717 (2007/10/02)
Conditions have been developed for optimizing ionic photobehavior material balances from alkyl bromides. Hydroxide ion as an efficient for the byproduct HBr while giving minimal competing photoreduction via electron transfer to the alkyl bomide. The photobehavior of bromides 1, 11, 25, and 40 has examined and with that of the corresponding iodides 2, 12, 26, 41 under conditions. In each case, the bromide higher yields of products derived from out of cage radical intermidiates than the corresponding iodide. However, with the 2-norbornyl bromides 11 and iodides 12 showed that, of products not formed from the out of cage 2-norbornyl radical 13, the bromides 11 gave a higher percentage of products from the ionic intermediates 15 and 16 than did the iodides. Thus, electron transfer within the radical pair 14 is apparently more rapid for bromides than iodides, as expected on the of the relative electronegativities of bromine iodine. It is that the substantially higher yields of out of radical products from alkyl bromides may be due in to formation of the radical pair with greater excess energy, which results in more rapid escape from the cage. The epimeric 2-norbornyl bromides 11x and 11n underwent no detectable interconversion and afforded somewhat different product ratios. The more hindered epimer 11n underwent conversion to products at a slower than 11x. By contrast, 12x and 12n underwent substantial interconversion via out of transfer of an iodine atom from iodide 12 to radical 13. Epimerization was significantly attenuated in the more viscous solvent tert-butyl alcohol.
Mechanism of Initiation of the Ring-opening Polymerization and Addition Oligomerization of Norbornene Using Unicomponent Metathesis Catalysts
Laverty, D. Theodore,Rooney, John J.
, p. 869 - 878 (2007/10/02)
The identities and yields of the low-molecular-weight products formed during ring-opening polymerization of norbornene in benzene solvent using several unicomponent metal halide catalysts (W, Mo, Re, Ru, Os and Ir) were extensively investigated.Dimers and
