Aqueous Dioxane Solution Research Articles

Catalytic hydrogenation of cardanol derived bifunctional monomers for polymerization with diesters

ABSTRACT. Cardanol extracted from cashew nut shell liquid (agro-waste) was used to synthesize a bifunctional monomer; methyl 16-(3-hydroxyphenyl)hexadecanoate using DTBPMB modified palladium catalyst. Hydrogenation of this monomer using a Ru(acac)3/triphos/MSA catalytic system in aqueous dioxane and ammonia solution gave 3-(16-hydroxyhexadecyl)phenol (75% yield) and 3-(16-aminohexadecyl)phenol (37% yield) respectively. Polymerization of 3-(16-aminohexadecyl)phenol and 3-(16-hydroxyhexadecyl)phenol with dimethyl nonadecanedioate (a di-ester obtained from methoxycarbonylation of methyl oleate) resulted into oligomers consisting of up to nine condensed monomer units (in the volatile fraction) as was revealed by MALDI-TOF MS.
 
 KEY WORDS: Cardanol, Bifunctional monomers, Catalytic hydrogenation, Polymerization
 
 Bull. Chem. Soc. Ethiop. 2022, 36(1), 173-186. 
 DOI: https://dx.doi.org/10.4314/bcse.v36i1.14 

On the kinetics of micellar polymerization. Acryloylaminoalkanoates case study

Polymerization of sodium salts of several acryloylaminoalkanoic acids was studied in aqueous micellar solution and in non-micellizing aqueous dioxane solution in wide concentration range. Some new observations in polymerization kinetics were made using UV–Vis-spectrometry, MALDI-TOF, and real-time conductomerty measurements. Conversions, polymerization rates and reaction orders were determined, mechanisms of initiation and termination are discussed. In micellar state monomer conversion close to 100% achieved in 3–5 min after polymerization starts whereas in homogeneous conditions conversions do not exceed 60% in two hours. Microemulsion mechanism of polymerization suggested for monomers capable to micellization or aggregation in solution. Semi-empirical model of micellar polymerization is discussed taking into consideration Kaler-Morgan model of microemulsion polymerization.

The bulk properties of dioxane solutions in ethylene glycol at 25–75°C

The densities of ethylene glycol solutions of dioxane were measured at 0–20 mol % dioxane at five temperatures ranging from 25 to 75°C. The apparent molar volumes of dioxane in the solutions were studied. The results were compared with similar characteristics of the aqueous solutions of dioxane and ethylene glycol solutions of tetrahydrofuran. In contrast to these systems, the ethylene glycol-dioxane system did not show a minimum of the apparent molar volumes of dissolved nonelectrolytes. The conclusion was drawn that the solvophobic effects were absent in the bulk properties of the ethylene glycol solutions of dioxane because of the low lability of the spatial net of H-bonds of ethylene glycol and peculiarities of the molecular structure of dioxane.

Synthesis and characterization of poly(AAm-co-BMA-co-AAc) hydrogels: effect of acrylamide content on swelling behaviour

Poly(acrylamide-co-butyl methacrylate-co-acrylic acid) hydrogels were prepared in various concentrations of a dioxane/water mixture as polymerization media using different percentages of cross-linker and by varying the amount of acrylamide over 4-fold in order to study the effect of acrylamide content on swelling behaviour of hydrogels. It was found that hydrogels prepared in 50% aqueous dioxane solution exhibited the highest swelling. The results also indicated that with increasing acrylamide content, swelling increased initially. And when acrylamide content further increased to 66% (based on total monomer), the swelling decreased gradually. Detailed swelling kinetics, such as swelling ratio, transport exponent n and diffusion coefficient D, were studied and the effect of pH on equilibrium swelling was also studied. The hydrogels were also characterized by network parameters, such as molecular weight between cross-links (M c) and cross-link density (q), that were determined to explain the swelling behaviour. The hydrogels were also characterized by Fourier transform infrared spectroscopy, elemental analysis, differential scanning calorimetry and scanning electron microscopy.

An Acid Catalysed Intramolecular C–C Coupling Reaction of 8-halomethyl-16-methoxy[2.2]Metacyclophanes

The hydrolysis of 8-bromomethyl[2.2]metacyclophane 1a with a methoxy group at the 16-position was carried out in an 80% aqueous dioxane solution by refluxing in the presence of Nafion-H (a solid perfluorinated resin sulfonic acid) as a catalyst. The reaction yielded the corresponding 8-hydroxymethyl[2.2]metacyclophane 3 and the intramolecular C–C coupling product 2 with a spiro skeleton.

New Hg2+-selective chromo- and fluoroionophore based upon 8-hydroxyquinoline.

A new 8-hydroxyquinoline derivative having an appended boron-dipyrromethene function has been prepared, and its metal ion sensing properties were investigated. The designed compound exhibited pronounced Hg(2+)-selective on-off-type fluoroionophoric properties among the representative transition- and heavy-metal ions in aqueous dioxane solution. The fluorescence was efficiently quenched more than 98% with 5 equiv of Hg(2+) ions, and the detection limit was found to be 5 x 10(-)(6) M in a dioxane-water (1:3, v/v) solvent system. The ionophore also showed a selective chromogenic behavior toward Hg(2+) ions by changing the color of the solution from light amber to red, which can be detected with the naked eye.

Kinetic stability of novel nitrile ylides

A series of relatively stable novel trifluoromethyl substituted nitrile ylides have been generated by base promoted elimination of hydrogen chloride from the corresponding imidoyl chlorides in acetonitrile and aqueous dioxane solution at 25 °C. The formation and decay of these sometimes highly coloured species was monitored spectrophotometrically. The rates of formation were first order in base, and the subsequent reaction with solvent was acid catalysed at high pH's in aqueous systems. Studies in aqueous dioxane indicated that the more stable ylides were also the slowest to form. In acetonitrile as solvent, the ylides underwent addition of solvent at rates which were independent of the base concentration and relatively insensitive to the nature of the substituents. In a number of cases, cycloaddition products were also isolated confirming the 1,3-dipolar nature of these compounds. Protonation of the ylides has also been studied both experimentally in aqueous solution and theoretically. While formation of nitrilium ions by protonation of the ylide carbon atoms is unlikely in aqueous solution since the corresponding amides are not observed as products, these ions have been calculated to be the most favoured protonated forms of ylides either in the gas phase or in a continuum of solvent, irrespective of its polarity. Ab initio calculations were carried out using molecular orbital methods (HF, MP2 and CCSD(T)) with basis sets ranging from 6-31G(d) to 6-311++G(3df,2p) and density functional theory (B3LYP) in conjunction with the polarizable continuum model (PCM) for treating non-specific solvent effects. This discrepancy between experiment and theory suggests a probable involvement of specific solvent interaction in inducing a higher thermodynamic stability of either nitrile carbon or NO2− oxygen protonated forms via hydrogen-bonded complexes.

A dibenzo-16-crown-5 fluoroionophore for selective emission ratio sensing of Na+ in basic aqueous dioxane solution †

For alkali metal cation sensing in aqueous dioxane solution, a novel dibenzo-16-crown-5 (DB16C5) fluoroionophore 1, N-(pyren-1-yl)-sym-(propyl)dibenzo-16-crown-5-oxyacetamide, has been synthesized. Examination of fluorescent behavior for 1 in 4∶1 1,4-dioxane–water (v/v) containing tetramethylammonium hydroxide (TMAOH) reveals that proton dissociation of the carboxamido moiety is promoted by Na+ binding, which results in an emission ratio response due to internal charge transfer (ICT) from the donor carboxamido anion to the pyrene acceptor. The emission intensity ratio (I459/I387) increases with enhancement of the Na+ concentration. No fluorescent response is induced by the presence of Li+, K+, or Cs+. This high Na+ selectivity is attributed to a preorganized structure of DB16C5 lariat ether binding site in which Na+ binds tightly to the carbonyl oxygen of the side arm to induce selective proton dissociation. Thus a ratiometric emission response with high Na+ selectivity has been obtained for 1 in 4∶1 1,4-dioxane–water (v/v) containing TMAOH.

Complexes produced by associated forms of porphyrin bound with hydrophobic–hydrophilic copolymer and transition metal ions

Properties of protonated dimeric forms of meso-tetraphenylporphine (TPP) and meso-tetra( p-aminophenyl)porphine (TAPP) bound with copolymer and also complexes produced by associated TAPP bound with copolymer, Mn 2+, and Fe 3+ are investigated by absorption, luminescence, and Raman spectroscopy. According to absorption spectra of protonated dimers of TPP, three dimeric forms of the porphyrin are observed in the ground state. However, selective excitation of these forms according to the fluorescence spectra reveals only two dimeric forms in the excited state. In contrast, similar selective excitation of TAPP bound with copolymer in aqueous–dioxane solution results in weak changes in the fluorescence spectra, nevertheless, there is strong interaction between porphyrin and macromolecular carboxyl groups in the ground state. In the case of the formation of the complexes between associated TAPP bound with copolymer, Mn 2+ and Fe 3+, a new band in the near IR region with a maximum at 840 nm is built up in the fluorescence spectrum. However, this near IR emission is completely quenched when new strong vibrational bands at approximately 1800 and 1900 cm −1 are revealed in the resonance Raman spectra of the complexes. The observed effects are explained in terms of direct participation of water molecules involved in the water–porphyrin dimeric complex in the processes of transformation of excitation energy. The involvement of water in this dimeric complex can lead to redistribution of flows of the energy degradation when transition metal ions play a role of the agent which enhances the trapping properties of the porphyrin–metal-ions complexes.

Enzymatic synthesis and various properties of poly(catechol)

Poly(catechol) was prepared by using peroxidase as a catalyst in two types of solvent systems: an aqueous dioxane solution and a reverse micellar solution. Peroxidases derived from two sources, horseradish (HRP) and soybean (SBP), were employed as catalyst. The structure of the prepared polymer was elucidated by infrared analysis. Enzymatically prepared film of poly(catechol) at a Pt electrode was subjected to cyclic voltammetric studies in aqueous HCl medium and phosphate buffer pH 6.5. Thermal studies of the polymer were performed by thermogravimetric analysis. The iodine-labelled polymers showed low electrical conductivity in the range of 10 −6 to 10 −9 S cm −1. The magnetic susceptibility and surface morphological property of the polymer were also studied.

Selective Colorimetry of Sodium Ion in Acidic Aqueous Media by Calix(4)crown Chromoionophore.

Selective colorimetry of alkali metal ions in aqueous dioxane solution by calix[4]crown chromoionophore possessing three dimensionally designed ion recognition site has been examined. Based upon a tautomerism from phenylazophenol to quinone hydrazone structure by forming MHL complex, chromoionophore was found to show a selective color change for Na+ in acidic aqueous media. In the same condition, no response was observed for Li+, K+, and TMA+.

Acid-base equilibria of air-water monolayers ofN-hexadecyl-8-hydroxy-2-quinolinecarboxamide

The surface pressure-area (π-A) isotherms ofN-hexadecyl-8-hydroxy-2-quinolinecarboxamide (HHQ) monolayers at an air-water interface on subphases with different pH values were investigated. The monolayer of HHQ was expanded and unstable on acidic subphases, while it was condensed and stable on basic subphases. The acid-base equilibrium of HHQ was investigated in an aqueous dioxane solution and at the air-water interface. The association-dissociation of HHQ with H+ ions in the interfacial region was very different from that in the aqueous dioxane solution. Some information regarding the packing density, phase transition and degree of ionization of the head group under different experimental conditions has been obtained.

Through-space electronic interactions of [2.2]metacyclophane benzyl cations

The hydrolysis of 8-bromomethyl[2.2]metacyclophanes 3 to the corresponding 8-hydroxymethyl derivatives 4 was carried out in 83% aqueous dioxane solution at 25°C. Substituent effect through space on the rate of the hydrolysis of bromomethyl groups attached on the opposite aromatic ring was first found in this investigation. Interestingly, the introduction of the substituents at the internal position 16 tends to enhance the hydrolysis reaction rate 10–100 times. It was found also that the stabilization by both the direct through-space cation-π-interaction and the interaction through the intra-annular 8,16-position are possible in the [2.2]metacyclophane 8-benzyl cations. The good correlation with log(K/KH) and σp+ was observed for the hydrolysis of internally unsubstituted 5-bromomethyl[2.2]MCPs 7, in which the direct through-space cation-π-interactions are not possible.

Stacking between Pyrido(3,2-f) (1,7)phenanthroline and Nucleic Bases

The stability constants of the ternary mixed ligand complex Cu(pdphen) (ATP)2-, where pdphen is the planar ligand pyrido(3,2-f) (1,7)phenanthroline, were determined by potentiometric pH titration in water, and in 30 and 50% (v/v) aqueous dioxane solutions. It has been observed from this information that a stronger stacking interaction between pdphen and the base of ATP exists and decreases with decreasing solvent polarity, i.e. increasing amounts of dioxane in the solvent mixture.

Complexation Behavior of Heterocyclic Hydrazones. II. Effects of Steric Factors on Formation Constants for Nickel(II) Complexes with Heterocyclic Hydrazones

Abstract The equilibria of nickel(II) ion with thirteen nitrogen-heterocyclic hydrazones (neutral form: HL) with and without blocking group(s) have been investigated spectrophotometrically in 28% aqueous dioxane solution at 25 °C and an ionic strength of 0.2 (KCl). For a series of 2-pyridinecarbaldehyde 5-substituted-2-pyridylhydrazones, the following linear free energy relationships (LFER) were derived between the overall formation constants, β1, β1′, and β2, of Ni(HL)2+, NiL+, and Ni(HL)22+ complexes, respectively, and the dissociation constants, Ka1 and Ka2, of H3L2+ and H2L+, respectively: log β1 = 0.95 (pKa1 + pKa2)/2 + 4.60, 1/2 log β2 = 0.95 × (pKa1 + pKa2)/2 + 4.82, and log β1′ = 1.40 (pKa1 + pKa2)/2 + 9.73. The steric effects of the 6-methyl group in pyridine and the quinolyl ring in place of pyridyl group on the complex formation were evaluated on the basis of LFER. The complex stabilization effect of the pyridyl group substituted for formyl hydrogen was also evaluated for Ni(HL)22+, Ni(HL)2+, and NiL+ complexes. These results together with LFER were discussed in conjunction with the thermodynamic parameters for the formation of Ni(HL)2+ complex and the ligand field parameters, Dq, for Ni(HL)2+ and Ni(HL)22+ complexes.

Preparation and reactivity of metal-containing monomers. 24. Equilibrium in solutions of metal(II) complexes with methacroylacetone

Stability constants of Mg, Ca, Sr, Ba Mn, Co, Ni, Cu, and Zn complexes with the polymerizable ligand methacrylacetone have been determined in aqueous-dioxane solutions at an ionic strength of μ=0.1 at 22°C. The methacroylacetone was shown to contain ∼30% in the enol form using the pH-meter method. The stability sequence of the transition-metal complexes corresponds to the Irving — Williams stability series for ligands of low molecular weight; for the alkaline-earth metals the stability of the complexes increases with increase in ionic radius. Methacroylacetone-based chelates are significantly less stable than their analogs with unsubstituted acetylacetone.

Pervaporation through structurally unstable polymeric membranes

According to the nature of interaction of polyethylene terephthalate (PET) with binary solutions two groups of systems have been identified. Those belonging to group A are aqueous solutions of acetone and dioxane, as well as acetone solutions of isopropanol. Systems belonging to group B are: acetonecarbon tetrachloride, dioxanecarbon tetrachloride and dioxanehexane. They are characterized by a positive deviation of swelling from additivity and a smooth trend of the crystallinity and permeability curves. The treatment of PET films with group A solutions is a simple method of modifying the polymer structure, leading to an increase in its permeability. Preliminary biaxial orientation of PET renders it suitable for use in the separation of liquids which crystallize an unoriented polymer so strongly that it loses its mechanical strength.

Photolysis of 2-azido-3,4,6-trichloro-5-cyanopyridine

The photolysis of aryl and hetaryl azides is accompanied by"the elimination of a molecule of nitrogen with subsequent ring expansion [1] or contraction [2]. To study the photolytic transformations of pyridyl azides with acceptor substituents we carried out the photolysis of 2-azido-3,4,6-trichloro-5-cyanopyridine (I) [3]. The reaction was accomplished in aqueous dioxane solution at room temperature and was complete after 1.5 h; the product was 4,5,7-trichloro-6-cyano-lH-1,3-diazepin-2(3H)-one (V), which was obtained in 72% yield.

A conductance investigation of HCl in aqueous solutions of tetrahydrofuran, dimethoxyethane and dioxane

Conductance of dilute solutions of HCl in water-tetrahydrofuran (THF), water-dioxane and water-dimethoxyethane (DME) were measured and the data processed using the Justice-Ebeling equation to evaluate the limiting conductance ΛO, the association constant KA and the apparent distance of closest approach a'. The Friedman-Rasaiah Gurney cosphere overlap term d+−/kT was calculated from a' values and illustrates the different solvation pattern of dioxane compared to that found for THF and DME. It would appear that dioxane can solvate cations more strongly due to its ability to form a boat configuration around a cation. The association constants are reasonably reproduced by the Bjerrum equation using realistic molecular dimensions of the ions involved for the distance of closest approach. The limiting conductance in the mixtures illustrates clearly the different mechanism for proton conductance compared to that for the cesium ion. The dielectric constants, viscosities and densities of the solvent mixtures were measured and are reported. The lowest dielectric constant for each type of solvent mixture was about 10.

Acid-Catalyzed Cleavage of Methoxymethyl Phenyl Sulfoxide. Solvent Effects and Mode of Bond Cleavage

Abstract Rate constants for the acid-catalyzed hydrolysis of methoxymethyl phenyl sulfoxide increase with increasing composition of dioxane in aqueous dioxane solution in contrast to the isomeric sulfenate which is strongly decelerated by added dioxane fraction (up to 90 vol%). The isotope distribution in the products obtained from the [18O]-sulfoxide was examined in 95 vol% aqueous dioxane. About 90% of the 18O was retained in the product S-phenyl benzenethiosulfinate from the reaction with hydrochloric and hydrobromic acid while only 50–60% of the 18O was found in the thiosulfinate from the reaction with perchloric acid. A plausible reaction mechanism involving ligand coupling within a hypervalent intermediate is proposed for the partial loss of the 18O label in the latter reaction.