The reentrant crystallization of like-charged colloidal particles in electrolyte solutions was studied to clarify the relationship between the shape of the phase diagram and the particleparticle effective potential. Coexisting densities were calculated at various electrolyte concentrations using the thermodynamic perturbation expansion method with effective one-component models. The effective potentials were obtained using an integral equation theory for liquids. Some model effective potentials were examined. The calculated results indicated that the reentrant behaviors of various acidic protein solutions observed in the experiments required not only the nonmonotonic dependence of the short-range attraction on the electrolyte concentration, but also the absence of a long repulsive tail.
Photoreactions of 4-(tribromomethyl)-4-methyl-2,5-cyclohexadienone (1) and its derivatives with amines were studied. Irradiation of 1 with amine produced 4-bromo-5-methyltropone (2) along with 4-(dibromomethyl)-4-methyl-2,5-cyclohexadienone (3). The effects of solvent, added water, and the structural variation in amine on the product ratio were explored. Isolation of the amine-derived products revealed that oxidative dealkylation of amine proceeded during the photoreaction. On the basis of the results obtained, a reaction mechanism involving fragmentation of the dienone anion-radical and amine cation-radical pair is proposed. Photoreactions of dienone 4 with amine produced the tropones 6 and 7, whereas tropone 9 was produced from 8. Trialkyltin radical-induced reductions of dienones 1 and 4 with tri-n-butyltin hydride demonstrated common features with the photoreactions. It was also found that irradiation of dienone 3 with amine produced 4-methyltropone (10).
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1998 photochemistry, radiation chemistry, chemoluminescence photochemistry, radiation chemistry, chemoluminescence O 0160
-045Photoreaction of Halomethyl Substituted Benzocyclic Ketones with Amines: Radical Cyclization and Ring Expansion Reactions Promoted Through Photoinduced Electron-Transfer Processes.-The title reaction of ketones like (I) affords especially the corresponding ring expansion products (II) and (V) via a photoinduced electron-transfer reaction between (I) and Tms-CH 2 -NEt 2 . -(HASEGAWA, E.; TAMURA, Y.; TOSAKA, E.; Chem.
Die O‐Alkenylalkylderivate des Dimedons (III) ergeben unter Bestrahlung die tricyclischen Cyclobutanderivate (IV), die über zwei verschiedene Ringöffnungsreaktionen die makrocyclischen Diketolactone (VII) liefern.
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