Hydrocarbons 9,10-dimethylanthracene

For example, simple fluorescence intensity measurements on dispersed hydrocarbon probes such as anthracene [17], perylene [18], pyrene [6,17,22], 9,10-dimethylanthracene (DMA) [60], and coumarin dyes [62] have confirmed that PMAA displays pH-dependent solution behavior. A marked decrease in the intensity of the probe occurs between pH 5 and 6, which coincides with the conformational transition of PMAA as determined by classical methods [2-4,47-50]. Two interrelated effects account for this behavior the solubilizing capacity of the polymer promotes an increase in the concentration of the probe in the solution [6,17,18,60,62] and because the intensity of the fluorescence observed is proportional to the excited state population the resulting emission is enhanced. The hydrocarbons may also be considered to be preferentially solubilized within the hydrophobic domains or structures of the hypercoiled state [6,22]. This results in a degree of protection from the deactivating effects of the aqueous phase and a concomitant increase in the fluorescence observed [6,17,18,22,60,62]. 

Most of the classical dienes are hydrocarbons, like cyclopentadiene. butadiene, anthracene, 9,10-dimethylanthracene, isoprene, 2,3-dimethylbutadiene. For dienes of this kind it is generally true that electrophilic dienophiles are the most reactive, and actually acrylic derivatives, maleic anhydride, p-benzo-quinone and similar compounds have found a large use as dienophiles both for preparative purposes and for kinetic studies. The latter demonstrated quantitatively the importance of electronegative groups on the dienophiles, and conversely of electron-releasing substituents on the diene, in order to accelerate such type of Diels-Alder reaction. It was also realised later that Diels-Alder additions with inverse electron demand , that is between electrophilic dienes and nucleophilic dienophiles, do occur . ... 

The radical anions can be prepared by the reaction of a fluorescent aromatic hydrocarbon such as 9,10-dimethylanthracene, with an alkah metal (lithium, sodium or potassium) in an ether solvent (1,2-dimethoxyethane, tetrahydrofuran or 2-methyltetrahydrofuran. 

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