Abstract: A group of novel polynuclear heterocyclic compounds having a diazaphenalene skeleton. These compounds assume orange to reddish violet colors according to the types of substituents on the diazaphenalene skeleton, and have excellent thermal stability and weatherability and good dispersibility in polymeric materials. They are useful as orange to reddish violet pigments, especially for coloring polymeric materials.

Abstract: A compound of the following formula ##STR1## wherein R represents an alkyl group containing 1 to 4 carbon atoms or a phenyl group; X.sub.1 represents a chlorine or bromine atom; Y represents the group of the formula ##STR2## WHEREIN X.sub.2 and X.sub.3 each represent a chlorine or bromine atom, and n is an integer of 2 to 4; and ring A may be substituted by an alkyl group containing 1 to 4 carbon atoms and or a halogen atom.The compound of formula (I) can be easily produced by reacting a quinoline derivative of the formula ##STR3## wherein R, X.sub.1 and the ring A are the same as defined above, with an aryldicarboxylic acid or its reactive derivatives.The compounds of formula (I) are useful as yellow organic pigments.

Abstract: A process for nitrating halogenated benzene derivatives which comprises reacting in the vapor phase a halogenated benzene derivative with at least one member selected from the group consisting of nitric acid, nitrogen dioxide and nitrogen pentoxide in the presence of at least one solid inorganic oxide selected from the group consisting of silica, alumina and silica-alumina.

Abstract: A process for separating dimethyl naphthalenes having a component comprising 2,6-dimethyl naphthalene in the form of complexes with a complex-forming compound, which comprises contacting a dimethyl naphthalene isomer mixture comprising at least 2,6-dimethyl naphthalene or a hydrocarbon mixture containing said dimethyl naphthalene isomer mixture with a complex-forming compound selected from the group consisting of nitro compounds of 2,6-naphthalene dicarboxylic acid, trimellitic anhydride and 2-chloro-5-nitrobenzoic acid, thereby to form a mixture of complexes of the dimethyl naphthalenes with said complex-forming compound having a main component comprising a complex of 2,6-dimethyl naphthalene with the complex-forming compound, and separating the complexes in the solid state from the reaction mixture.