Polyene Compounds

Isomerization of Polyene Compounds. Intramolecular rearrangement of Fe(CO)3(polyene) compounds are somewhat similar to the fluxional behaviour described above. Though one is concerned with acyclic rather than cyclic polyenes, and with 7r-bonding rather than a-bonding changes, the shift isomerizations (19) (20) (21) could be considered analogues 

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Tlie tautomerism of heteroaromatic compounds is intimately related to the problem of aromaticity and antiaromaticity (87MI1,94MI1), this being especially true for the compounds of this chapter, which are borderline between these showing Fliickel behavior and polyenic compounds (nonaromatic). 

Linear polyenes. The measurement of membrane processes requires fluorophores inserted into cell membranes. Suitable fluorophores are polyene compounds such as diphenylhexatriene (DPH) (see Fig. 6.8) or parinaric acid, used in several occasions as... 

Raney-nickel was found to be selective in the hydrogenation of cyclopentadiene and cyclohexadiene and of their methyl and ethyl derivatives at 0-40 °C and 2-5 bar pressure137,138. The skeletal nickel proved to be selective in the semihydrogenation of conjugated polyenic compounds (equation 52)139. 

Opisthobranch are marine mollusks that are scarcely protected by a shell, which suggests that they possess defensive substances.1 1 For instance, when the Pacific aglajid Navanax inermis is damaged by enemies, it secretes a bright-yellow water-insoluble mixture into its slime trail. From the extracts, three major compounds have been isolated and identified as polyenic compounds 51-53, navenones A-C.122,123 It has been demonstrated that these secreted constituents induce an avoidance-alarm response in a trail-following Navanax species at a concentration of lOpmoll M24... 

III. Some Photochemical Transformations of Polyenic Compounds Related to... 

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