Titration Curves of p-Aminobenzoic Acid-Formaldehyde-p-Bromoaniline Copolymers in Nonaqueous Media

Copolymers obtained by condensation of p-aminobenzoic acid, p-bromoaniline, and formaldehyde in presence of acid catalyst have been separated into five fractions. Quantitative estimation of Br in each of the fractions was carried out, and the total amount of acidic and basic functional groups in given weight of the copolymer was calculated. Each of the fractions were titrated potentiometrically and conductometrically in nonaqueous solvents, and an excellent correlation was obtained for calculated and observed functional groups. The titration curves also indicated a series of breaks which bear an integral relation to each other. These features have been interpreted in terms of intramolecular hydrogen bonding, homoconjugation, and composition of the copolymers.     

Progress report on the boundedness character of third-order rational equations

An interpretation of Cull's enveloping method used to determine global asymptotic stability of one dimensional population models is given. This is done by relating the enveloping property with the existence of a global Lyapunov function. Following this spirit we revisit a result of Liz.     

Effect of Hydrogen Bonding on the Dissociation of Some Mixtures of Phenolic Oligomers in Nonaqueous Media

Some structurally and molecularly uniform phenolic oligomers with additional functional groups have been prepared by known methods of stepwise synthesis, and their dissociation behavior in nonaqueous solvent has been studied by electrometric titration techniques. Hyperacidity and stepwise neutralization of some of the functional groups in the oligomer molecules have been interpreted in terms of intramolecular hydrogen bonding, homoconjugation, and ion association in a medium of low dielectric constant.     

Single crystal-to-single crystal irreversible transformation from a discrete vanadium(V)-alcoholate to an aldehydic-vanadium(IV) oligomer

An unprecedented single crystal-to-single crystal transformation occurs when a binuclear oxovanadium(V) compound [V(V)(2)O(2)(L)(2)] 1 involving 2,6-bis(hydroxymethyl)-p-cresol (H(3)L) as a bridging ligand is exposed simultaneously to white light and aerial oxygen to generate an oligomeric compound [V(IV)(2)O(2)(L*)(2)] 2 (H(2)L* is 3-hydroxymethyl-5-methylsalicylaldehyde). Each vanadium(V) center in 1 is reduced to vanadium(IV) in 2 at the expense of a two-electron alcohol-to-aldehyde oxidation in the coordinated ligand. The additional electron being released is possibly consumed by molecular oxygen to generate hydrogen peroxide.     

Facile allylboration of ketones with β-benzyloxy-γ,γ-difluoroallylboronate: Preparation of gem-difluorinated homoallylic tert-alcohols

The reaction of β-benzyloxy-γ,γ-difluoroallylboronate, at room temperature and in the absence of catalysts, with a variety of aromatic and aliphatic ketones of varying sterics and electronic requirements furnishes fluorinated homoallylic tert-alcohols in 62-82% yields. Representatives of these alcohols were converted to their corresponding α,α-difluoro-β-hydroxy ketones in 73-85% yields.