Reactions of Bis-dithiophosphonic Acids with 3-Hydroxypyridine and 3-(Hydroxymethyl)pyridine

Russian Journal of General Chemistry - Bis-dithiophosphonic acids reacted with 3-hydroxypyridine and 3-(hydroxymethyl)pyridine at a molar ratio of 1:2 to produce pyridinium salts which showed a...     

Reactions of diborane with aromatic heterocycles—21: Reactions with nitrogen-containing heterocycles related to pyridine

The reactions of solutions of B₂H₆ in ethers with a variety of aromatic heterocycles containing one or more six-membered rings with only one nitrogen per ring have been examined. Quinoline and isoquinoline form monoborane adducts which hydroborate in the presence of an excess of B₂H₆. Protonolysis gives the 1,2,3,4-tetrahydro-compounds in both cases. N-Methylquinolinium and N-methylisoquinolinium iodides both hydroborate. Hydroboration and halogen loss occur with 2-, 3- or 4-haloquinolines (chlorine or bromine). Prior to hydroboration 8-hydroxyquinoline forms a borane adduct which rapidly eliminates one equivalent of hydrogen in a probable intramolecular ring closure. Sodium 8-hydroxyquinolinate combines with B₂H₆ in an unsymmetrical cleavage reaction to form B₂H₇^? or BH₄^?, and the same ring closed product formed by 8-hydroxyquinoline. Phenanthridine and N-methylphenanthridinium iodide both readily undergo hydroboration. The products formed by the latter with B₂H₆ are 5-methyl-5,6-dihydrophenanthridine-borane and an iodoborane etherate. 1,8-Naphthyridine forms a transient borane complex which rapidly undergoes hydroboration; protonolysis gives 1,2,3,4-tetrahydro-l,8-naphthyridine. 2,2′-Bipyridyl undergoes a complex reaction with one equivalent of BH₃ giving a mixture of bpy·2BH₃ and hydroborated products, but 4,4′-bipyridyl does not appear to hydroborate. 1,10- and 1,7-Phenanthroline both hydroborate giving a mixture of reduced products on protonolysis. Pyridine-borane and 2-phenylpyridine-borane both decompose in refluxing diglyme, but protonolysis gives no reduced products in either case.     

4-(5-nonyl)pyridine extraction of platinum from different aqueous solutions

The partition of tracer-level (<10^?7 mole/l) platinum between various 4-(5-nonyl)-pyridine phases and aqueous nitric, hydrochloric, and sulphuric acid phases has been studied radiometrically as a function of the amine and acid concentrations. The effects of saltingout agents and some anions on the extraction of the metal are reported. The extraction data is compared with that of gold and conditions are established for the separation of daughter¹⁹⁹Au from neutron irradiated platinum. The distribution coefficients of various metal ions are given for the 4-(5-nonyl)pyridine-10M HCl system and their factors for separation from platinum estimated.     

Molecular solutions of cellulose in mixtures of ionic liquids with pyridine

New systems suitable for determination of molecular characteristics of cellulose, mixtures of ionic liquids based on 1-n-alkyl-3-methylimidazolium with pyridine, were found. In ionic liquid-pyridine mixtures, cellulose is dispersed on the molecular level. The cellulose-ionic liquid-pyridine systems with 1-ethyl-3-methylimidazolium acetate and 1-ethyl-3-methylimidazolium diethyl phosphate are stable in time. The dynamic viscosity and refractive index of the mixtures can be controlled by varying the ionic liquid to pyridine ratio. The viscometric and dynamooptical properties of cellulose in these mixtures were compared with those in Cadoxen.     

Reactions of hydrated electrons with pyridinium salts in aqueous solutions

Rate coefficients for the reactions of the hydrated electron (e(aq)(-)) with pyridinium salts in aqueous solutions have been determined using pulse radiolysis techniques. The rate coefficients for pyridine, 1-hydropyridinium chloride, and 1-hydropyridinium nitrate were observed to be 1.4 x 10(10), 4.5 x 10(10), and 5.3 x 10(10) M(-1) s(-1), respectively. The e(aq)(-) was found to primarily attack the pyridine ring, the proton coordinated to the nitrogen atom, and the nitrate counterion, but not the chloride. Results for the corresponding dimer structures of 4,4'-dipyridyl, 1,1'-dihydro-4,4'-bipyridinium dichloride, and 1,1'-dihydro-4,4'-bipyridinium dinitrate had similar trends for e(aq)(-) attack sites. The rate coefficients for pyridinium salts were lower when the pyridinium nitrogen atom is coordinated to a methyl group rather than to a proton. This reduction is probably due to the increase in electron density of the pyridine ring due to the electron-donating methyl group. Pyridinium salts are not major contributors to the production of molecular hydrogen in the radiolysis of aqueous solutions and actually decrease molecular hydrogen yield due to scavenging reactions of the e(aq)(-). The yield of molecular hydrogen decreases from 0.45 to approximately 0.2 molecule/(100 eV) over the scavenging capacity range for the e(aq)(-) of 10(5)-10(9) s(-1). Absorption spectra of the transient species produced by the reactions of pyridinium salts with OH radical and H atom formed in water radiolysis were observed, and rate coefficients for these reactions were determined.     

Reactions of reducing radicals with 2- and 3-nitroanilines in aqueous solutions: a pulse radiolysis study

Reactions of 2- and 3-nitro anilines (2- and 3-NA) with e_aq⁻, H-atoms and one-electron reductants have been studied using pulse radiolysis in aqueous solutions. Reactions of e_aq⁻ were found to be quite fast with both 2-NA and 3-NA resulting in their corresponding semi-reduced species which are reducing in nature. Reduction potentials for 2-NA/2-Na^•′ have been estimated to be approx. −0.56 Vvs. NHE and that for 3-NA/3-NA^•− was found to be between −0.185 V and −0.45 Vvs. NHE. Semi-reduced 2-NA has main absorption peak at 300 nm with a shoulder in the 350 nm region and a broad weak band in the 470–500 nm region, whereas semi-reduced 3-NA possesses an absorption peak at 520 nm. Reducing radicals such as (CH₃)₂ C^•OH and CO₂^•− reacted with 2-NA, producing semi-reduced species, whereas reactions of these radicals with 3-NA produced their corresponding radical-adduct species.     

Pulse radiolysis of pyridine and methylpyridines in aqueous solutions

The radicals formed from pyridine, 3-methylpyridine, 3,5-dimethylpyridine, 2,6-dimethylpyridine and 2,4,6-trimethylpyridine by attack of H, e^-_aq, OH and O^•- in acqueous solutions were investigated by pulse radiolysisin the pH-range 1–13.8. The UV-vis. absorption spectra as well as the formation and decay kinetics for the protonated and unprotonated forms of the methylpyridine radicals studied are presented. The pK_a-values for the OH-adducts were determined.     

Reactions of alkyl-radicals with gold and silver nanoparticles in aqueous solutions

Silver and gold nanoparticles are very efficient catalysts for the dimerization of methyl-radicals in aqueous solutions. The rate constants for the reaction of methyl-radicals with the gold and silver nanoparticles were measured and found to be 3.7 x 10(8) M(-1) s(-1) and 1.4 x 10(9) M(-1) s(-1), respectively. The results thus suggest that alkyl-radicals, also not reducing ones, are scavenged by these nanoparticles. This might explain the role, if such a role exists, of these nanoparticles in medical applications.     

Reactions of cycloalkeno -1,2,3-selenadiazole with nucleophiles

Reactions of cycloalkeno-1,2,3-selenadiazole and various nucleophiles were studied. In the case of 5-membered ring fused 1,2,3-selenadiazole, nucleophilic attack on selenium atom exclusively resulted in a formation of vinyl selenide derivatives.     

Functionalization of the pyridine ring. 1. Reactions with carbon-carbon bond formation (review)

A review is presented for advances in the direct introduction of alkyl, alkenyl, alkynyl, aryl, and hetaryl substituents into the pyridine ring over the past IS years.     

Reactions on polymers with amine groups. V. Addition of pyridine and imidazole groups with acetylenecarboxylic acids

Unsaturated macromolecular carboxybetaines were obtained by reaction of poly(4-vinylpyridine) and poly(N-vinylimidazole) with propiolic acid. A kinetic model was presented for 4-methylpyridine. It consists of three coupled reactions: neutralization, addition which involves two molecules of acid and leads to a cation–anion pair structure, where the cation results from the addition of the amine nitrogen to the triple bond of acid, and an equilibrium reaction between the ion-pair structure and the betaine structure. The addition rate was found to be higher for poly(4-vinylpyridine) than for poly(N-vinylimidazole); it was also higher in water than in a water–methanol mixture. The reaction with acetylenedicarboxylic acid was carried out on poly(N-vinylimidazole), but the transformed units showed the structure that results from propiolic acid. The betaine products from 4-methylpyridine did not polymerize by radical initiation. The polymeric products show characteristics of photocrosslinking polymers. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1615–1623, 1998     

Stability constants of complexes formed by some metal ions with 2-(phenyliminomethyl)pyridine and 2-(o-hydroxyphenyliminomethyl)pyridine

The stability constants of some metal complexes of these two reagents have been determined.