Pyridine Bases Research Articles

CATALYTIC EFFECTS IN THE AMINOLYSIS REACTIONS OF ARYLSULPHONIC ACID DERIVATIVES IN NON-AQUEOUS MEDIA

Abstract The catalytic effects of organic bases in reactions of arylamines with arylsulphonic acid derivatives, ArSO2X (X = Cl, Br, OSO2Ar) in aprotic media are characterised by the following regularities. 1. The activity of 3- and 4-substituted pyridines, N-alkyl- and N-phenylimidazoles is desribed by the common Bränsted relationship. Substituents in positions 2 and 2,6 of the pyridine molecule have a strong steric influence. Tertiary cyclic amines of quinuclidine type with the same basicity as pyridines and imidazoles have more higher activity than the latter. N-Oxides of pyridine which are 4–5 pKa units less basic than the corresponding pyridines have the catalytic activity 100 times as much, as compared with them. 2. The intensity of the catalytic action of pyridines and their N-oxides alters insignificantly with changing the leaving group X in the substrate, somewhat increasing in the order Cl < Br≤OSO2Ar. 3. The activity of pyridine bases increases with increasing the solvent solvating ability. The inhibiting influence of the X− anione on the rate of catalytic reaction displays in media of high polarity (nitrobenzene, acetonitrile). These regularities are explained in terms of the nucleophilic mechanism of catalysis which is supported by isolating intermediate adducts of tertiary amines (in particular 4-N,N-dimethylaminopyridine) with arylsulphonic acid bromides and anhydrides and by studies of their reactivity towards arylamines in methylene chloride. Compounds of bifunctional nature (carboxylic acids) do not accelerate the reaction under consideration unlike a similar substitution process at the carbonyl C-atom. The cause of this seems to be a different geometry of transition states in substitution at the sulpho group S-atom and at the carbonyl carbon, respectively.

ChemInform Abstract: HYDRAZIDO(2‐)‐COMPLEXES OF MOLYBDENUM AND TUNGSTEN FORMED FROM DINITROGEN COMPLEXES BY PROTONATION AND LIGAND EXCHANGE

AbstractDurch Reaktion der cis‐Distick stoffkomplexe (I) mit konz. Halogenwasserstoffsäuren werden die neuen Hydrazido komplexe (II) erhalten.

Cadmium-113 nuclear magnetic resonance studies on some pyridine base adducts of cadmium(II) β-diketonates and thio-β-diketonates

Cd-113 NMR spectra of cadmium(II) β-diketonates and thio-β-diketonates have been measured in several solvents. The influences of coordination of sulfur atom and pyridine base on chemical shift were discussed for these complexes.

Qualitative analysis of shale oil acids and bases by porous layer open tubular gas chromatography and interfaced vapor phase infrared spectrophotometry

Characterization of components in the acid and base fractions of shale oil has been achieved by means of selective extraction followed by gas chromatographic separation of individual phenolic and heterocyclic nitrogen base compounds on a stainless steel porous layer open tubular, free fatty acid phase column. Interfaced rapid scan vapor phase infrared spectrophotometry (VPIR) allowed informative spectra to be obtained for microgram component peaks, computer data handling giving improved measurement sensitivity. Qualitative identification of substituted phenolics and pyridine bases was achieved by coordination of retention data, VPIR, and mass spectral data. 7 figures, 3 tables.

Interaction of excited molecules of 9,10-dimethylphenazine with pyridine bases

Interaction of excited molecules of 9,10-dimethylphenazine with pyridine bases

Isotropic proton nuclear magnetic resonance shifts of adducts of bis(β-ketoesterato)nickel(II) complexes

The isotropic proton magnetic resonance shifts of the pyridine base adducts of bis(β-keto-esterato)nickel(II) complexes were measured. The slow exchange of γ-picoline was observed at room temperature. When a temperature was raised, the relative shift ratio among three signal of γ-picoline closely resembled to that in the case of bis(acetylacetonato)nickel(II) complex. With regard to the spin delocalization onto β-ketoesters, it was suggested by INDO calculations that ligand-to-metal β spin transfer was mainly responsible for it.

Pyridine base adducts of manganese(II) and iron(II) complexes of TTA and STTA

Octahedral high-spin adducts of the type ML 2B 2, where M = Mn(II) and Fe(II), L = thenoyltrifluoroacetone and monothiothenoyltrifluoroacetone and B = pyridine and γ-picoline, were isolated in the atmosphere and the properties of these adducts were investigated to clarify the effect of the sulfur-coordination. The assignments of the metal-ligand stretching bands in IR spectra were performed. The frequencies of these bands followed the Irving-Williams order in most cases and suggested the soft character of Fe(II) to sulfur atom. The values of isomer shift and quadrupole splitting of Mössbauer spectra in Fe(II) complexes of STTA revealed the contribution of π back-donation to a great extent.

Spectrophotometric study of adducts of nickel-5 nitro-8-quinolinate with heterocylic and other nitrogen bases

Abstract Adduct formation constants have been determined by spectrophotometric study of the organic base-adducts of nickel (II) chelate of 5-nitro-8-quinolinol in a monophase-chloroform. Bathochromic and hypsochromic shifts were observed in the optical spectra, in visible range, due to adduct formation. A penta coordinated square-base pyramidal structure is proposed for the low pK pyridine base adducts whereas hexa coordinated octahedral structure is favoured for adducts with bases of higher pK values. The stabilities of the nickel adducts increase in the following order of the base: 2,4-lutidine

Isotropic PMR shifts in pyridine base adducts of Mn(II), Fe(II) and Ni(II) complexes of TTA and STTA

Isotropic proton magnetic resonance shifts of γ-picoline solvent containing some adducts of the type ML 2B 2, where M = Mn(II), Fe(II) and Ni(II), L = thenoyltrifluoroacetone and monothiothenoyltrifluoroacetone and B = γ-picoline, have been measured. Slow exchange rate of the base was observed evidently in Ni(II) adducts. The small contribution of the pseudo contact shift to the isotropic shifts was verified, and the observed contact shifts were discussed from the viewpoint of ligand to metal and metal to ligand spin transfers. The calculated fractions of metal to ligand α spin transfer in the three kinds of metal ions were well correlated with the numbers of unpaired electrons in t 2 g orbitals.

Vinylogous nucleophilic catalysis: hydrolysis of ethenesulphonyl chloride in the presence of pyridine bases

Evidence is presented that hydrolysis of ethenesulphonyl chloride (2a) in the presence of pyridine bases takes place by the route (2a)→(5)→(3a), i.e. by vinylogous nucleophilic catalysis.

Physical and chemical properties of squarate complexes. II. Mössbauer spectroscopy and magnetic susceptibility studies of several dimeric and trimeric iron(III) complexes containing the squarate dianion

Products obtained by the reaction of certain bases with μ-dihydroxo-bis[squaratodiaquoiron(III) dihydrate, [Fe(C 4O 4)(H 2O) 2(OH)] 2·2H 2O, I, have been isolated and studied by the complementary methods of 57Fe Mössbauer spectroscopy and magnetic susceptibility. Reaction of I with pyridine or substituted pyridine bases gives materials with formula [Fe(C 4O 4)(L) 2(OH)] 2·2H 2O where L = pyridine, 4-methylpyridine, or 3-methylpyridine. The Fe 2(OH) 2 bridging unit is maintained in these complexes as evidenced by their variable-temperature magnetic susceptibility behavior. The data are very well described with a HDVV S 1= S 2 = 5 2 dimer model where J ≅−8 cm −1 and g = 2.00. Dimethylsulfoxide (DMSO) reacts with I to give a μ 3-oxo complex containing coordinated DMSO, [Fe 3O(C 4O 4) 3(DMSO) 3(H 2O) 3](OH). Magnetic susceptibility data for this complex are analyzed with a HDVV S 1 = S 2 = 5 2 trimer model by assuming equivalent spin sites. Results of this analysis give J = −39 cm −1 and g = 2.00. The proposed trimeric structure of this complex is also inferred from the presence of a strong infrared absorption near 550 cm −1 assigned to the FeO stretching mode, V asym(Fe 3O). Reaction of I with KOH in ethanol yields a material whose magnetic susceptibility versus temperature behavior is indicative of a S 1 = S 2 = 5 2 dimer with J = 96 cm −1 and g = 2.00. Presence of a strong infrared absorption at 820 and 750 cm −1, assigned to the FeOFe stretching mode,v asym(Fe 2O) is additional evidence for the proposed μ-oxo structure for this complex, [Fe(C 4O 4)(H 2O) 2] 2O. Mössbauer spectral parameters for these ferric squarate complexes are consistent with proposed structures.

Determination of thermodynamic functions by means of infrared spectroscopy. The accuracy in -ΔH determination; Formation of complexes phenol-pyridine and its homologues

Values of thermodynamic functions -ΔH, -ΔG, and -ΔS of the complex formation between molecules of pyridine (and its methyl derivatives) and phenol in CCl4 solutions were determined using infrared spectroscopy. After optimalizing experimental conditions the error in -ΔH determination does not exceed 0.2%; this accuracy is sufficiently high to investigate the influence of substituents on the pyridinic nitrogen basicity. The values of -ΔH determined in this way correlate linearly with values of ionization constants of pyridine bases.

ChemInform Abstract: CATALYST FOR HETEROAROMATIZATION OF ALIPHATIC IMINO COMPOUNDS

AbstractPropyliden‐allyl‐amin (I) cyclisiert bei 250°C in Gegenwart von Nickel‐Aluminiumoxid zu den Pyridinen (II) und (III).

Solvent extraction of cobalt(II) with 8-quinolinol and its analogues in the presence of some heterocyclic nitrogen bases

Pyridine and its 2-methyl, 2,4-dimethyl and 2,4,6-trimethyl derivatives enhance the extraction of cobalt(II) into chloroform in the presence of 8-quinolinol and its 2-methyl, 4-methyl, 5-chloro and 5-nitro analogues. Adduct formation constants were determined for the cobalt(II) chelates, which formed diadducts with the pyridine bases. The special role of steric factors is discussed. The results are consistent with Lewis acid-base concepts.

Excess enthalpies in pyridine base-methanol systems

The excess enthalpy of mixing versus composition was studied at 293.15 K and 303.15 K for some binary mixtures of methanol with pyridine bases. The results are presented in Tables.

AN INFRARED STUDY OF THE BASICITY OF NON‐AROMATIC IMINES: RELATION TO VISUAL PIGMENTS

Abstract— The knowledge of the basicity of non‐aromatic Schiff‐bases is important for the interpretation of the photochemical primary step of vision. In order to obtain an estimate of it, the infrared spectra in chloroform d solution of a number of aliphatic amines, pyridine derivatives and non‐aromatic Schiff‐ bases have been measured. From the known pKa values of the aliphatic and pyridine bases and the free‐associated frequency shift (Av) of the C—D. N hydrogen bonds, the pKa values for the Schiff‐bases were inferred. They range from 6 to 8. 5, less basic than aliphatic amines but somewhat more basic than pyridine bases.

IR-spectroscopic studies of the interaction of pyridine bases with vanadium and molybdenum oxides supported on magnesia

As shown by IR-spectroscopic studies, pyridine bases interacting with V2O5 and MoO3 supported on MgO form hydrogen bonds with surface hydroxyls and coordinate bonds with V and Mo ions. The interaction of 2,6-dimethylpyridine adsorbed on the surface with oxygen leads to the formation of 6-methylpyridine-2-carboxaldehyde, whose formyl group interacts with surface hydroxyls.

Catalyst for heteroaromatization of aliphatic imino compounds

Ni/Al2O3 is an active catalyst for the heteroaromatization of aliphatic imino compounds; the selectivity of forming the pyridine bases on Ni/Al2O3 is higher than in the presence of Al-K and Al-Cr-K catalysts.

Reaction of bis (?-aminoethylato) ethanolamineaquochromium chloride [(NH2CH2O)2Cr�(NH2CH2CH2OH)�H2O]C1 with aldehydes

1. In bis(β-aminoethylato)ethanolamineaquochromium chloride only one of the three amino groups reacts with aldehydes. The condensation is accompanied by the elimination of acetaldehyde and rupture of the C -N bond, and leads to the aldimine. 2. The formed coordinated aldimine exhibits a high activity in the crotonic type of condensation and is quickly converted to a polyunsaturated ligand, which then is cyclized to either the pyridine or quinoline base.

ChemInform Abstract: PYRIDINE‐BASE COMPLEXES OF THE TETRACHLOROPHOSPHONIUM ION

AbstractDie Komplexbildung zwischen Tetrachlorophosphonium‐Ionen, im allgemeinen als Hexachloroantimonatw) eingesetzt, und ein‐ sowie zweizähnigen Pyridinen werden in Lösung (Nitrobenzol, ‐methanol, ‐ethanol) NMR‐spektroskopisch untersucht.