Structure of the dibenzoylphthalic acids obtained by condensation of pyromellitic dianhydride with benzene

Conclusions A method has been developed for the isolation of 2,4-dibenzoylisophthalic and 2,5-dibenzoylterephthalic acids from the mixtures formed during the Friedel-Crafts condensation of pyromellitic dianhydride with benzene. The structure of the acids obtained has been investigated by PMR and DR speetroscopy. The ability of 2,5-dibenzoylterephthalic acid to undergo tautomeric interconversions (normal or cyclic forms) has been discovered.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 368–372, February, 1976.     

Some problems of nonequilibrium copolycondensation

The influence of the reactivity of the starting compounds and reaction conditions on the formation of the macromolecules of copolymers has been investigated for a nonequilibrium copolycondensation in solution by acceptor-catalytic polyesterification. In the nonequilibrium copolycondensation in solution, copolymers with different distributions of units may be formed, depending on various factors. Introduction of all amounts of acid chloride (intermonomer) in the beginning of the nonequilibrium copolycondensation leads to the formation of copolymers with statistical distribution of the units independent of the difference in reactivity of the comonomers used. For synthesis of copolymers with a block structure by one-stage nonequilibrium polycondensation in solution the initial comonomers must have different reactivities (r ≠ 1) and the rate of intermonomer introduction must be lower than that of its reaction with the more reactive comonomer. On varying the above factors, block copolymers with different lengths of block segments may be obtained.     

Addition of N,N-dichloroarylsulfonamides to unsaturated compounds

Russian Chemical Bulletin -     

Protonation of metal carbonyl complexes : VII. Proton NMR spectra and stereochemistry of protonated forms of π-cyclopentadienylphosphinemanganese complexes

¹H NMR measurements show that protonation of the complexes π-C₅H₅Mn-CO)_3-n(PR₃)n (n = 1 and 2) with CF₃COOH occurs at the manganese atom, the spectra revealing “hydride” signal at δ values of -4 to -6 ppm. The stereochemistry of the protonated forms has been determined from the ¹H  ³¹P couling pattern.