Use Of Pyridine Research Articles

Determination of Hydroxyl Number in Polymers by Infrared Spectroscopy

Hydroxyl number is a term that reflects the number of hydroxyl groups in a molecule. Hydroxyl number determination is important in polymer analysis to determine the extent of reaction or number of hydroxyl groups available for further reaction. There exist many methods for chemical determination, and these vary with polymers, degree of solubility, ease of reaction, and catalyst. There also exist other methods including GC, GPC, and IR methods. Other methods for hydroxyl determination in oils and with the use of near-IR have been reported. The wet chemical methods for hydroxyl number determination in polymers are accurate and precise but can take hours to run. Although this time can be reduced by running several samples simultaneously, running just one sample would take about 3–4 h because of required reaction and titration times. The chemical method requires the use of pyridine, dimethylaminopyridine, and acetic anhydride, which are irritating, highly toxic, and corrosive chemicals. In order to reduce these problems with the chemical hydroxyl number determination, the feasibility of an analysis of the polymers by infrared (IR) spectroscopy was studied with the use of the Nicolet PLS Quant program.

ChemInform Abstract: Rhodium‐Catalyzed Hydroformylation of Formaldehyde in Pyridines.

AbstractDie Hydroformylierung von Formaldehyd (I) in Gegenwart von Rh‐Katalysatoren wie (II) wird in verschiedenen Pyridinen (III) als Lösungsmittel untersucht.

Characterization of NiO supported on zeolite Y, by pyridine adsorption

A series of bifunctional catalysts with different loadings of NiO supported on a HY ultrastable zeolite, have been characterized by pyridine and NO adsorption. A characteristic i.r. band assigned to pyridine coordinated to Ni +2 ions has been found at 1612 cm −1. This band allows one to distinguish Ni 2+ from other cations (Na +,La 3+) and metallic nickel, and also to quantify the dispersion of accessible Ni +2, in good agreement with the results from NO adsorption. The use of pyridine makes it possible to characterize, at the same time, the surface acidity of the acid component of the bifunctional catalyst.

Synthesis of Amides and Amidines by Reaction of Carboxylic Acids and Amines in the Presence of Polyphophoric Acid Trimethylsilyl Ester (PPSE)

Abstract The reaction between amines and carboxylic aicds in the presence of polyphosphoric acid trimethylsilyl ester (PPSE) has been investigated from the view point of the synthesis of amides and amidines. Benzanilide was selectively prepared from benzoic acid and aniline in the presence of PPSE and pyridine at 100 °C, whereas a mixture of benzanilide and N,N′-diphenylbenzamidine was obtained without the use of pyridine. The reaction at 160 °C almost exclusively gave N,N′-diphenylbenzamidine. Various symmetrical amidines were obtained from combinations of carboxylic acids and aromatic amines in high yields by simply heating at 160 °C with four molar amounts of PPSE. The reactions of aliphatic and aromatic amines with N-monosubstituted and N,N-disubstituted amides also afforded corresponding unsymmetrical amidines under the same conditions. The reaction mechanism is discussed in some detail.

RHODIUM-CATALYZED HYDROFORMYLATION OF FORMALDEHYDE IN PYRIDINES

Abstract The use of pyridines as a solvent greatly enhances the catalytic activity of RhCl(CO)(PPh3)2 for the hydroformylation of formaldehyde. The yield of glycol aldehyde goes up to over 90% under mild conditions. At temperatures above 100 °C, however, the reaction is complicated by the aldol addition of glycol aldehyde yielding straight-chain sugars.

Synthesis of high molecular weight polyester carbonates via interfacial phosgenation of aromatic dicarboxylic acids and bisphenols

AbstractThe synthesis of bisphenol A poly(carbonate–ester) copolymers was studied by phase‐transfer catalysis and modified interfacial polymerization. Only low molecular weight copolymers were prepared directly from dicarboxylic acids, phosgene, and bisphenol A by an interfacial process that involves the use of pyridine as catalyst, HCl acceptor, and weak base. To avoid the use of tertiary amines, which can be difficult to remove from the polymer products, and to produce higher molecular weight copolymers from the same dicarboxylic acid precursors another synthetic method was developed. This more effective method required careful pH control that was achieved by the selective use of the weak‐base potassium carbonate in the first stage of the process. Moreover, elevated reaction temperatures (∼65–70°C) and phase‐transfer catalysis were used. The carbonate–ester copolymers prepared by this technique had consistently high intrinisic viscosities, little or no anyhydride microstructure, and higher degrees of ester unit incorporation than those produced by the pyridine‐catalyzed method. These copolymers also had glass transition temperatures (Tg) 20–30°C higher than bisphenol A polycarbonate homopolymer. An analytical method for determining quantitatively the amount of ester units in the bisphenol A poly(carbonate‐esters) was developed by using Fourier transform infrared spectroscopy (FT‐IR). Agreement between this FT‐IR method and a quantitative nuclear magnetic resonance (NMR) method was found to be reasonable, especially for copolymers with ester unit percentages lower than 40%.

New insights into aliphatic nucleophilic substitution reactions from the use of pyridines as leaving groups

New insights into aliphatic nucleophilic substitution reactions from the use of pyridines as leaving groups

The use of pyridine and piperidine hdn as probe for activity of molybdenum-based hydrotreatment catalysts. The role of the nickel (part II)

The reactions of pyridine and piperidine HDN have been used as a probe for testing the activity and the selectivity of eleven hydrotreating catalysts in the absence of sulfur: these comprised pure alumina, doped alumina, MoO 3/Al 2O 3, NiMo and CoMo/AI 2O 3. The piperidine HDN reaction needs only single Bronsted or Lewis acidic sites while the pyridine reaction needs at least a bifunctional site with a reduced centre and an acidic centre. The intervention of a trifunctional site, two reduced centres and an acidic one, explains the promoting effect of the nickel. The presence of this new site can be correlated with the existence of a phase where the nickel, in the reduced state, “decorates” the Mo oxide layer. This new phase will have as a precursor the xNiO molybdate phase proposed by Knozinger et. al. [11].

Manufacture and Use of Pyridine and Its Derivatives

Manufacture and Use of Pyridine and Its Derivatives

Catalytic reactions of pyridines. VI. Heterogeneous vapor-phase ring alkylation of pyridines with alcohols over H+-, Li+-, and alkaline earth cation-exchanged zeolites.

The heterogeneous vapor-phase alkylation of pyridine with methanol was examined over metal cation-exchanged X-and Y-type zeolites in an atmosphere of nitrogen. β-Methylation was observed over H+-or Li+-exchanged zeolites, whereas α-and γ-methylation (the former occurred in preference) were observed over alkaline earth cation-exchanged zeolites. For example, at 400°C, the yields of α-, β-, and γ-picolines over the HY catalyst were 2.6, 12.2, and 2.6%, whereas those over the BaY catalyst were 22.7, 3.8, and 7.6%, respectively. This catalytic ring alkylation over metal cation-exchanged zeolites was also examined by the use of pyridine with ethanol and picolines with either methanol or ethanol.

Studies on the metabolism of unsaturated fatty acids. V. Isomerization of thiol esters of cis-2-alkenoic acids during their preparation and alkaline hydrolysis.

N-Acetylcysteamine and coenzyme A esters of cis-2-alkenoic acids have been found to undergo isomerization to the corresponding trans-isomers during their preparation by the mixed anhydride method and also during their alkaline hydrolysis. The isomerization might proceed by interaction of the free thiol group and the cis-double bond of 2-alkenoic thiol esters. The use of pyridine as a base and three or more equivalents of the mixed anhydride to the thiol compound prevented the formation of the trans-isomer. Addition of hydrogen peroxide during alkaline hydrolysis also prevented the isomerization completely.

Size exclusion chromatography of organically bound metals and coal-derived materials with inductively coupled plasma atomic emission spectrometric detection

Organometallic and metalloorganic compounds have been separated by size exclusion chromatography using pyridine eluent. A directly interfaced inductively coupled plasma atomic emission spectrometer was used for detection of these metal-containing species. Problems relating to the use of pyridine in the chromatography of these species are discussed. Most problems appear to be related to non-carbon-bound metal systems. The application of this technique to solvent-refined coal fractions and process solvent is presented. Evidence of solvent selectivity for some of the organically bound metals in the solvent refined coal is given.

Partial esterification of poly(vinyl alcohol) with acid chlorides

AbstractThis work deals with some features of the reaction of organic acid chlorides with poly(vinyl alcohol). The structure of the modified polymers was determined by means of IR, UV and NMR spectroscopy as well as by chemical analysis. Vinyl alcohol‐vinyl butyrate copolymers were obtained by reaction of poly(vinyl alcohol) with n‐butyryl chloride without any catalyst. The reaction appeared to satisfy a second order kinetics for conversions no higher than 50%. The activation energy found was of 9.9 kcal/mol. The use of pyridine as a catalyst involved a noticeable increase of the reaction rate, but this effect was found to be independent of the acid chloride used. When triethylamine was used as a catalyst, β‐keto ester groups were found to be grafted onto the polymer chain. The steric hindrance of these groups were thought to be sufficiently important for the conversion to reach a limit of about 30%. The observed swelling in water of vinyl alcohol‐vinyl butyrate copolymers made it reasonable to conclude that the hydrophilic character of the copolymers decreased progressively when the ester group content increased.

Notiz zur Synthese von ω‐Phenylalkylderivaten durch Addition von Benzylquecksilbersalz an Alkene

Note to the Synthesis of ω-Phenylalkyl Derivatives by Addition of Benzylmercury Salts to Alkenes While reaction of benzylmercury acetate and NaBH4 with electrophilic ethyl acrylate gives the addition product 4-phenylbutyric acid ester, the reaction with less electrophilic styrene and allylbenzene affords the expected addition products in moderate yields only by use of pyridine as solvent and addition of di-2-pyridylamine as a complexing reagent.

Hydroformylation of phenyl-substituted olefins with cobalt catalysts

A study of the hydroformylation of styrene, α-methylstyrene, allylbenzene and trans-propenylbenzene catalysed by octacarbonyldicobalt has shown that use of pyridine as a catalyst activator has a marked influence on the selectivity of the reaction and that the isomeric composition of the aldehydes is strongly dependent upon the temperature. Deuterium scrambling was observed in the hydrogenation and hydroformylation products concurrently formed from 2-phenylpropene-1 d 2-3 d 3 even at p(CO)  100 atm.

Periodate oxidation analysis of carbohydrates: Part IX. Evaluation of the use of pyridine as reaction solvent for oxidation of water-insoluble carbohydrate materials

Oxidation of methyl glycopyranosides with periodic acid in pyridine was studied by analysis of the reaction products by the dithioacetal method. Both C 2—C 3 and C 3—C 4 bonds were cleaved yielding three types of dialdehydes;secondary attack of these dialdehydes by periodic acid did not occur. Oxidation in aqueous pyridine proceeded in normal Malapradian fashion, but more slowly than for oxidation in water. Molar proportions of aldehydes were theoretical, when methyl glycosides were oxidized with periodic acid in a 1:1 ( v v ) mixture of pyridine and water. The structures of carbohydrate moieties in a few saponins and glycolipids were confirmed by analysis of the oxidation products obtained under similar conditions.

Polystyrene resins with immobilized polyamines: Preparation, characterization, and ability to bind Cu(II) ions

AbstractThree polyamine ligands, ethylenediamine (EDA), diethylenetriamine (DTA), and triethylenetetramine (TETA), were bound to three chloromethylated “popcorn” polystyrene resins (16, 50, and 100% phenyl ring substitution) with the use of pyridine as the reaction medium. The rate of chloride displacement decreased with increasing molecular weight of the amine and higher degree of resin chloromethylation, while the extent of multiple attachments to the polymer matrix increased. The additional crosslinking, a result of multiple attachments, caused the polyamine resins to swell to a lesser extent in pyridine and water. The ability of the insoluble polyamine–polystyrene resins to chelate Cu2+ ions from dilute solutions (200 ppm) was determined at pH 5. With EDA resins the capacity for Cu2+ increased with increasing amount of the bound polyamine, with DTA it remained unchanged, while with TETA it was found to decrease.

Photopolymerization of methyl methacrylate and some other vinyl monomers with the use of a pyridine–bromine charge‐transfer complex as photoinitiator

AbstractPolymerization of MMA was carried out under visible light (440 nm) with the use of pyridine–bromine (Py–Br2) charge‐transfer (CT) complex as the photoinitiator. Initiator exponent and intensity exponent were 0.5 and 0.43, respectively, and the monomer exponent was found to be dependent on the nature of the solvent or diluent used. The Polymerization was inhibited in the presence of hydroquinone, but oxygen had very little inhibitory effect. An average value of kp2/kt for this polymerization system was 1.19 × 10−2, and the activation energy of photopolymerization was 4.95 kcal/mole. Kinetic data and other evidence indicate that the overall polymerization takes place by a radical mechanism. With Py–Br2 complex as the photoinitiator, the order of polymerizability at 40°C was found to be MMA, EMA ≫ Sty, MA.

Hydrogen Exchange Reactions of Sulfilimines and Sulfoximines

Abstract Alkyl phenyl sulfilimines, benzyl phenyl sulfilimine and the corresponding sulfoximines were found to exchange their α-hydrogens with deuteriums in heavy water when the medium was alkaline. No exchange was observed when the medium was acidic or neutral. The rates of exchange in a sulfilimine were greater than those of the corresponding sulfoximine. The kinetics of these H-D exchange reactions were investigated by use of pyridine as a catalyst, and the reaction mechanism was discussed.

Use of Pyridine in the Conductometric Measurement of Hop Alpha-Acids

(1967). Use of Pyridine in the Conductometric Measurement of Hop Alpha-Acids. Proceedings. Annual meeting - American Society of Brewing Chemists: Vol. 25, Proceedings of the Annual Meeting 1967, pp. 119-123.