Roland Bonneau

Giant pulse laser photolysis of benzene and mesitylene

Abstract Using a flash photolysis apparatus in which the excitation was provided by a giant pulsed neodymium laser giving 100 mJ at 2645A after two frequency doublings, we have looked for transient absorptions in benzene and mesitylene dissolved in cyclohexane or ethanol. We have observed in the 4000–6000A range a transient absorption that we assign to a singlet * -singlet * transition ( 1 E 1u ← 1 B 2u ). In addition, three other transients appear with lifetimes approximatively equal to 300 ns, 450 ns and few microseconds. Assignment of these three transients is tentatively discussed.

Purification des colorants thiaziniques, Azur A, Azur B, Azur C, par une méthode de partage

Resume On a separe les uns des autres, ainsi que de la thionine et du bleu de methylene, des derives N-methyles de la thionine au moyen dextraction en tetrachlorure de carbone a partir dune solution aqueuse tamponnee au pH approprie pour chaque compose. On peut utiliser la methode pour purifier les colorants.

Formation of indolizines by the addition of α-chloroacrylonitrile to pyridinium ylides: regioselectivity and Hammett correlation

Cycloaddition of pyridinium ylides to α-chloroacrylonitrile give indolizines: the regioselectivity of the reaction can be rationalized in terms of nucleophilic attack by the ylides on the olefin.