Absolute Methanol Solutions Research Articles

Characterization and thermal analysis of thiourea and bismuth trichloride complex

Abstract A complex of thiourea and bismuth trichloride has been synthesized. Its composition is Bi3Cl9[SC(NH2)2]7. Crystallographic data are a = 7.141(2) A, b = 8.820(3) A, c = 16.365(5) A, α = 99.389(4)°, β = 95.422(4)°, γ = 106.177(4)°, triclinic system. There are the mononuclear anion [BiCl5SC(NH2)2]2− and the dinuclear cation {Bi2Cl4[SC(NH2)2]6}2+ with the Bi–Cl–Bi bridge bonds in the complex. The electric conductance of the absolute methanol solution contained the complex indicates that the complex is an ionic compound. Raman spectra indicate that the bismuth ion is coordinated by the sulfur atoms of the thiourea. The thermal analysis verifies the structure of complex. The TG–MASS curves show the structure rearrangement in the complex at about 118 °C. The DSC curves and calculation means that the structure rearrangement is irreversible.

Dissociation and electrooxidation of formic acid at platinum in nonaqueous solutions as probed by in situ surface-enhanced Raman spectroscopy

Surface-enhanced Raman spectra (SERS) from a roughened platinum electrode in formic acid-containing dimethylformamide solutions have been examined combined with cyclic voltammetry techniques. The occurrence of surface poisoning by CO adsorption was confirmed by observation of both Pt–CO and internal CO modes simultaneously. Oxidation of HCOOH can occur to a large extent only after the desorption of CO from the surface. Similar observations were also obtained in absolute methanol solutions. Linearly bound CO on platinum was suggested for both nonaqueous systems. In addition, a high electro-catalytic activity for the present roughened SERS-active platinum surface was also assumed compared with smooth platinum surfaces.

Infrared spectroelectrochemistry of the oxidation of absolute methanol at a platinum electrode

Abstract Infrared spectroelectrochemistry has been used to identify the products of the oxidation of methanol at a polycrystalline platinum electrode in absolute methanol solutions. A spectroelectrochemical cell, with potential control under ambient conditions and optical path under vacuum, provided spectra which were free of H 2 O and CO 2 vapour absorptions. The SNIFTIRS potential step technique was used to obtain absorbance difference spectra which indicated that methyl formate was the major methanol oxidation product in acidic, neutral, and alkaline methanol solutions. CO 2 and formate ion were also shown to be significant products under alkaline conditions. Spectra recorded with different infrared polarisations gave no evidence of adsorbed intermediates or adsorbed oxidation products.

Synthesis of Proton-Ionizable p-Nitrophenol-Containing Tetraazacrown and Diazadithiacrown Ethers from an Aromatic Building Block Prepared via the Einhorn Reaction

A series of p-nitroanisole-containing tetraazacrown (14−18), diazacryptand (22), and diazadithiacrown (23−25) macrocycles has been prepared by treating the appropriate secondary diamine, diazacrown, or dimercaptan with 2,6-bis[(2-chloroacetamido)methyl]-4-nitroanisole (BB). Five of these p-nitroanisole-containing macrocycles were reported earlier. Four new bis(p-nitroanisole)-containing macrocycles resulting from a 2 + 2 macrocyclization of diamine or dimercaptan with BB were also isolated. Six of the p-nitroanisole-containing macrocycles (16, 17, 22−25) were converted to the p-nitrophenol-containing macrocycles (27−32) on treatment with LiI in refluxing pyridine. Thermodynamic quantities (log K, ΔH, and TΔS) for the interactions of four new compounds (24, 27, 31, and 32) with Na+, K+, Ba2+, Ag+, and Pb2+ were evaluated by calorimetric titration at 25.0 °C in either 70% or absolute methanol solution. The compounds show strong interactions with Ag+ and Pb2+ but very weak interactions with Na+, K+, and Ba2+...

Synthesis and Characterization of a New N-Alkylated Azacrown Ligand and its Transition Metal Complexes

A new pendant-arms macrocyclic ligand 3,4:9,10:17,18:23,24-tetrabenzo-5,8,19,22-tetraoxa-1,12,15,26-tetraazacyclooctacosane N.N′,N″,N′″-tetraacetic acid (H4L) was synthesized by alkylating 3,4:9,10:17,18:23,24-tetrabenzo-5,8,19,22-tetraoxa-1,12,-15,26-tetraazacyclooctacosane with BrCH2COOK in absolute methanol solution. H4L contains a coordinated potassium ion. Its transition metal complexes were also prepared in high yields. All compounds were characterized by IR, NMR, elemental analyses, UV-VIS and TG-DTA. The complexes have the formula [M2KL]Cl·nH2O (M = Co(II). Zn(II), Cd(II), Hg(II): n = 2∼2.5) except Ni2L·5H2O and [CuKH2L](ClO4) · 3H2O. Referee I: S. Bott Referee II: K. Moedritzer

Synthesis and Characterization of a New N-Alkylated Azacrown Ligand and its Rare Earth Metal Complexes

A new pendant-arms macrocyclic ligand 3,4:9,10:17,18:23,24-tetrabenzo-5,8,19,22-tetraoxa-1,12,15,26-tetraazacyclooctacosane N,N′,N”,N”′-tetraacetic acid (H4L) was synthesized by alkylating 3,4:9,10:17,18:23,24-tetrabenzo-5,8,19,22-tetraoxa-1,12,15,26-tetraazacyclooctacosane with BrCH2COOK in absolute methanol solution. H4L contains a coordinated potassium ion. Its rare earth metal complexes were also prepared in high yields. All compounds were characterized by several physical methods. The complexes have the formula [MKL]·nH2O (M = Ln, n = 3–8.5). Referee I: K. Moedritzer Referee II: H. M. Goff

Adsorption kinetics of electrode processes and the mechanism of Kolbe electrosynthesis: Part I. Adsorption of carboxylic acids and the nature of the particles chemisorbed on platinum electrodes

The adsorption of acetic acid, its halogenates and homologues on a platinum electrode has been studied in a wide range of potentials. The adsorption of carboxylic acids is observed throughout the potential range studied (0–2.7 V), and in aqueous solutions there are three characteristic regions: an irreversible destructive chemisorption, resulting from dehydrogenation or dehalogenation at the α-carbon atom, in the potential range 0–0.5 V with a maximum of adsorption at E r ≈ 0.2–0.3 V; a fully reversible adsorption of anions (or anion-like particles) from the potential of zero free charge to 1.5 V with a maximum at 0.8 V, associated with the anions being displaced by the adsorbing oxygen as the value of the potential becomes more positive; and an adsorption region, 1.6–2.7 V, with a maximum at Er ≈ 2.3 V, to a considerable extent corresponding to the reversible adsorption of carboxylic acid anions on the surface oxide layers formed. The drop at E r, ≈ 2.3 V is associated with the discharge of anions and the occurrence of Kolbe synthesis. In contrast to aqueous solutions, in absolute methanol solution monotonic growth of the surface coverage with the reversibly adsorbed carboxylic acid anions is observed up to the moment when the process of Kolbe electrosynthesis starts.

Some specific features of the catalytic role of UPD foreign metal adatoms and water on the anodic oxidation of absolute methanol on Pt

In this work the influence of underpotential-deposited foreign metal adatoms on the anodic oxidation of methanol on Pt in absolute methanol solutions of H 2SO 4 and LiClO 4 is studied. Unliked aqueous solutions, the underpotential deposition (upd) of heavy metal ions causes striking catalytic effects for methanol oxidation in absolute methanol solutions. The maximum catalytic activity occurs at particularly high positive potentials where the upd monolayers are already anodically dissolved. An alternative interpretation based on double layer changes as a result of the redissolution of the upd monolayer has been postulated. The effect of small additions of water on the processes both on Pt and Pt/M(upd) surfaces has also been examined.

PROPERTIES OF CELLULOSE HYDROXAMIC ACID DERIVATIVE AND ITS METAL-CHELATING COMPLEXES

Hydroxamic acid derivatives were prepared from dialdehyde celluloses obtained by periodate oxidation of cellulose according to an improved method for the preparation described by Gal'braikh and Rogovin (Vysokomol, Soedin., 5, 693 (1963)). Mild oxidation of the dialdehyde celluloses with acidified sodium chlorite led to 2, 3-dicarboxy celluloses, which gave the dimethyl esters by treatment at room temperature under the presence of large amounts of methanol containing 0.06-0.1N hydrogen chloride without causing degradation by methanolysis. The esters were converted into the corresponding hydroxamic acid derivatives by the action of an absolute methanol solution of hydroxylamine adjusted at pH 9.2-3 by newly prepared sodium ethylate. The hydroxamic acid derivatives were found to be isolated in a yield of more than 80% as sticky massive solid from the reaction mixture by shaking with a mixture of EtOH:H2O (80:20 v/v). The formation of the hydroxamic acid derivatives was confirmed by analyses of the nitrogen content and the characteristic coloration with ferric chloride solution. Some properties of the metal chelating complexes of hydroxamic acid derivatives prepared were investigated. The hydroxamic acid derivatives formed chelating complexes of colored precipitates with copper or ferric ion, but the chelating complexes formed by such ions as cobalt, nickel and zinc gave no precipitate. After uptake of metallic ions by the hydroxamic acid derivatives from the mixture, the contents of metallic ions remaining in the supernatant separated by centrifugation were determined by the chelatometric titration method. By this determination, it was proved that the hydroxamic acid derivatives had a high ability to take up such specific ions as ferric or copper ion preferencially from their mixture with other kinds of metallic ions. This findings suggests that the hydroxamic acid derivatives from cellulose may be useful as a material for recovery of the specific ions.

Specific features of electrooxidation of alcohols on platinum in absolute alcohol solutions. Role of water in chemisorption and dehydrogenation processes

The specifics of electrooxidation of alcohols in absolute alcohol solutions were studied to show that the mechanism of the process differs from that of alcohol electrooxidation in aqueous solutions. In absolute alcohol solutions, the rate-determining step of the process involves direct electron transfer from the alkoxy ion (in alkoxide or alkaline solutions) or the alcohol molecule (in acid or salt solutions) to the electrode with formation of an alkoxy radical. The effect of the alcohol nature, background nature and concentration, and the catalyst-electrode nature on alcohol electrooxidation was investigated. The work involved a comparative study of the state of the Pt electrode surface and of methanol adsorption in aqueous and absolute methanol solutions. In absolute methanol solutions, methanol adsorption was shown to be weaker and not destructive to adsorbing molecules. The influence of water on the adsorption and kinetics of electrode processes on a Pt electrode in methanol solutions was also studied.

Study of monensin complexes with monovalent metal lons in anhydrous methanol solutions

Potentiometric and cyclo-voltammetric studies have been carried out on monensin anion (Mon−) complexes with the alkali ions as well as with Tl+ and Ag+ in absolute methanol solutions. The log Kf values obtained for the complexity constants and corrected for the activity effects are: Li+, 3.3±0.1; Na+, 6.72±0.05; K+, 5.18±0.05; Rb+, 4.58±0.05; Cs+, 3.75±0.05; Tl+, 5.31±0.05; Ag+, 8.2±0.2. It is seen that for the alkali, the most stable complex is formed with Na+. The enthalpy and entropy of complexation with the sodium ion were found to be ΔHo=−5.47±0.24 kcal-mole−1 and ΔSo=+12.4±0.7 e.u. The complex, therefore, is enthalpy and entropy stabilized.

Cinnoline chemistry. XI. The ultraviolet spectra of halogen substituted 4‐hydroxy‐ and 4‐mercaptocinnolines

AbstractThe ultraviolet spectra of a series of 4‐hydroxy‐ and 4‐mercaptocinnolines substituted with fluorine, chlorine or bromine in the 5‐, 6‐, 7‐ and 8‐position have been obtained in absolute methanol solution between 200 and 500 mμ. The spectra were used, to make structural assignments for the products of cyclization from mesoxalyl chloride, m‐fluoro‐and m‐bromophenylhydrazones.

Cobalt Color Reaction of Barbiturates.

Of the numerous analytical methods employed for the determination of barbiturates, those making use of specific color reactions have been most extensively studied. Handorf employed the mur-exide reaction for the detection of veronal, and Zwikker, Bodendorf, Herwick and Koppanyi, et al.,, have developed modifications of a color reaction with cobalt salts in conjunction with various bases. Kozelka and Tatum attributed this color formation to a specific reaction with substances containing one or 2 imide groups. In an investigation of amytal (isoamylethyl barbituric acid) excretion by dogs, using a modification of the reaction designed by Koppanyi et al., employing cobalt acetate and isopropylamine made up in absolute methanol solutions, it was observed in this laboratory, that of the more probable breakdown products of amytal only isoamyl-ethyl acetic acid gave the characteristic color reaction. Since this compound contains no imide grouping, it was apparent in this case that color formation was not due to such a group. This finding led to an examination of various classes of compounds a number of which have not been reported upon by other investigators. A partial listing is given in Table 1. Since the acids tested gave a color apparently identical with that obtained with amytal, a number of these test solutions were submitted to spectrophotometric analysis. The spectrophotometric curves given herewith were made with a Bausch and Lomb medium quartz spectrograph and sector photometer. The length of the absorption cells was 5 cm. To cobalt acetate and isopropylamine mixtures were added respectively, solutions of amytal, isoamyl ethyl acetic acid (RRC2H2O2) and stearic acid in amounts sufficient to give an intensity of color suitable for measurement.