Monofunctional Amines Research Articles

Extraction of Heavy Metals by Amines Adsorbed onto Silica Gel

Previous work has established the possibility of using known coordinating agents supported on silica gel in the removal of heavy metals such as lead, copper, cadmium, and nickel from aqueous media. Functionalized silica gel has been used in the removal of heavy metals with notable success. Silica gel is currently being used as a support for various monofunctional aliphatic amines as coordinating ligands. The current study reports the results of an investigation involving the use of saturated, straight chain primary amines as coordinating ligands in the removal of copper(II), cadmium(II), lead(II), nickel(II), and silver(I) ions from aqueous solutions of known concentration. Primary amines used in this investigation were n-butylamine, n-hexylamine, n-octylamine, n-decylamine, and n-hexadecylamine.

Explicit-solvent molecular dynamics simulation at constant pH: Methodology and application to small amines

A method is developed for performing classical explicit-solvent molecular dynamics (MD) simulations at constant pH, where the protonation state of each ionizable (titratable) group in a simulated compound is allowed to fluctuate in time, depending on the instantaneous system configuration and the imposed pH. In this method, each ionizable group is treated as a mixed state, i.e., the interaction-function parameters for the group are a linear combination of those of the protonated state and those of the deprotonated state. Free protons are not handled explicitly. Instead, the extent of deprotonation of each group is relaxed towards its equilibrium value by weak coupling to a “proton bath.” The method relies on precalibrated empirical functions, one for each type of ionizable group present in the simulated compound, which are obtained through multiple MD simulations of monofunctional model compounds. In this study, the method is described in detail and its application illustrated by a series of constant-pH MD simulations of small monofunctional amines. In particular, we investigate the influence of the relaxation time used in the weak-coupling scheme, the choice of appropriate model compounds for the calibration of the required empirical functions, and corrections for finite-size effects linked with the small size of the simulation box.

From dynamic mechanical properties to plastic strain behavior of epoxy networks. Effect of the network architecture

AbstractClosed epoxy networks with various architectures, i.e., crosslink density and chain flexibility between crosslinks, were considered in this study. The crosslink density can be varied by preparing epoxy‐amine networks from a mixture of primary amines having different functionalities using mixtures of poly(oxypropylene)amines or a monofunctional amine having the same chemical structure acting as a chain extender. The chain flexibility is modified by considering aliphatic epoxy prepolymers instead of aromatic. The influence of the architecture of the epoxy networks on the low‐ and high‐stress mechanical properties is discussed. The dynamic mechanical spectroscopy conducted in wide ranges of frequency and temperature gives insight into the molecular level analyzing the data in both the glass transition region (α‐relaxation) and sub‐Tg relaxation zones. A model described by Perez and based on the existence of nanofluctuations of density or quasi‐point defects and the concept of hierarchically correlated molecular motions are also used to describe the low‐stress mechanical behaviour. The same theory is extended by taking into account the large‐stress effects and used to analyze the stress‐strain curves recorded in compression at various temperatures and strain rates. This modeling can describe variation of the flow stress with temperature and gives a unique description of the yielding of all the epoxy networks. From this model, the main physical parameter determining the flow stress is the cohesion of the solid state resulting from intermolecular interactions; the loss of cohesion, as temperature increases, corresponds to the α‐process which depends on the network architecture. Finally, the strain and stress at break (sr and ϵr) recorded in tension at various temperatures and strain rates for epoxy networks having various crosslink densities are correlated with the low‐stress behavior from the shift factors, aT, determined in the glass transition region.

Polyamine co-matrices for matrix-assisted laser desorption/ionization mass spectrometry of oligonucleotides.

The analysis of oligonucleotides using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) has led to the investigation of the use of matrix additives (i.e., co-matrices) to help improve the poor spectral quality commonly observed during the analysis of this class of compounds. The use of certain matrix additives in MALDI-MS has been investigated previously, and these additives have been shown to enhance the desorption/ionization efficiency of oligonucleotides during the MALDI experiment. Specifically, amine bases, such as piperidine, imidazole, and triethylamine, have been shown to improve mass spectral quality as assessed by improved molecular ion resolution and increased molecular ion abundance. These improvements occur due to competition between the oligonucleotide and the co-matrix for protons generated during the MALDI event. Co-matrices with proton affinities near or above the proton affinities of the nucleotide residues serve as proton sinks during the desorption/ionization process. In this work, we have investigated the use of polyamines as co-matrices for MALDI mass spectrometric analysis of oligonucleotides. Spermine tetrahydrochloride, spermine, spermidine trihydrochloride, and spermidine were evaluated for their effectiveness at enhancing the mass spectral quality of oligonucleotides analyzed using MALDI-MS. The solution-phase pK( b) values and the gas-phase proton affinities of these polyamines were determined, and it was found that the polyamines appear to be more basic than the monofunctional amines investigated previously. The mass spectral data shows that spermidine and spermine are extremely effective co-matrices, yielding improved molecular ion resolution and molecular ion abundances. The spermine co-matrices are more effective than the spermidine co-matrices, but adduction problems with the spermine co-matrices limits their overall utility. In general, polyamine co-matrices are found to be more effective than monofunctional amine co-matrices at improving the mass spectral data obtained during MALDI-MS of oligonucleotides.

Polyamine co‐matrices for matrix‐assisted laser desorption/Ionization mass spectrometry of oligonucleotides

The analysis of oligonucleotides using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) has led to the investigation of the use of matrix additives (i.e., co-matrices) to help improve the poor spectral quality commonly observed during the analysis of this class of compounds. The use of certain matrix additives in MALDI-MS has been investigated previously, and these additives have been shown to enhance the desorption/ionization efficiency of oligonucleotides during the MALDI experiment. Specifically, amine bases, such as piperidine, imidazole, and triethylamine, have been shown to improve mass spectral quality as assessed by improved molecular ion resolution and increased molecular ion abundance. These improvements occur due to competition between the oligonucleotide and the co-matrix for protons generated during the MALDI event. Co-matrices with proton affinities near or above the proton affinities of the nucleotide residues serve as proton sinks during the desorption/ionization process. In this work, we have investigated the use of polyamines as co-matrices for MALDI mass spectrometric analysis of oligonucleotides. Spermine tetrahydrochloride, spermine, spermidine trihydrochloride, and spermidine were evaluated for their effectiveness at enhancing the mass spectral quality of oligonucleotides analyzed using MALDI-MS. The solution-phase pK b values and the gas-phase proton affinities of these polyamines were determined, and it was found that the polyamines appear to be more basic than the monofunctional amines investigated previously. The mass spectral data shows that spermidine and spermine are extremely effective co-matrices, yielding improved molecular ion resolution and molecular ion abundances. The spermine co-matrices are more effective than the spermidine co-matrices, but adduction problems with the spermine co-matrices limits their overall utility. In general, polyamine co-matrices are found to be more effective than monofunctional amine co-matrices at improving the mass spectral data obtained during MALDI-MS of oligonucleotides. Copyright © 1999 John Wiley & Sons, Ltd.

Etherification versus amine addition during epoxy resin/amine cure: Anin situ study using near-infrared spectroscopy

The reactions between a multifunctional epoxy resin, tetraglycidyl 4,4′-diaminodiphenylmethane (TGDDM) and a monofunctional amine, methylaniline (mAnil) are studied. Due to the existence of a tertiary amine catalytic center within the TGDDM molecule, the etherification reaction during cure of TGDDM is usually more significant than in other epoxide systems. The importance of this reaction relative to the amine addition reactions is investigated. In situ near-infrared spectroscopy is used to obtain kinetic data during the cure reactions. The reaction rate constants are calculated from linear regression analysis for both amine addition and etherification reactions based on the reaction mechanisms proposed. Arrhenius relationships are observed for all the reaction rate constants involved. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:895–901, 1998

Enantioseparation of amino compounds by derivatization with o-phthalaldehyde and d-3-mercapto-2-methylpropionic acid

o-Phthalaldehyde in combination with d-3-mercapto-2-methylpropionic acid is described as a chiral reagent for the enantioseparation of amino compounds. The reagent was applied to the optical resolution of α-amino acids, α-alkyl-α-amino acids, α-amino acid amides, α-alkyl-α-amino acid amides, β-amino alcohols and β-alkyl-β-amino alcohols. Separation of the diastereomers was carried out by reversed-phase chromatography and the derivatives were detected fluorimetrically. The diastereoselectivity obtained was compared with that of other commercially available chiral thiols. The rate of the reaction of various amino compounds with o-phthalaldehyde- d-3-mercapto-2-methylpropionic acid was studied, together with the stability of the derivatives obtained. Application of the method to the enantioseparation of chiral monofunctional amines was demonstrated by using α-methylbenzylamine as a model compound. The method described offers good enantioselectivity combined with high sensitivity for various chiral amino compounds derived from chemo-enzymatic processes.

The evolution of the viscoelastic retardation spectrum during the development of an epoxy resin network

AbstractThe evolution of the viscoelastic behavior of an epoxy resin at various stages of curing has been followed with the changes in the retardation spectrum. The creep J(t) and recoverable creep compliance Jr(t) curves of the neat epoxy resin Epon l00lF (Shell) were determined at temperatures between 30 and 77°C. The viscosity decreased over 8 orders of magnitude as the temperature was increased. Specimens with eight stages of network development were prepared by reacting all of the epoxy resin's oxirane rings with amine hydrogens from varying ratios of a monofunctional amine (methyl aniline) and a tetrafunctional amine 4,4′‐diamino diphenyl sulfone (DDS). Preparations in which 25, 35, and 40% DDS were used did not result in a molecular network, so they were viscoelastic liquids. With 45% DDS, the product had a nascent network and was judged to be just beyond the point of incipient gelation. The remaining preparations from 0.50, 0.60, 0.70, and 1.0 DDS yielded tighter less compliant molecular networks. The creep and recoverable compliance curves were measured over a range of temperatures above the glass transition temperature, Tg. They were reduced to Tg, and retardation spectra L(ln τ) were calculated.

Model Adherend Surface Effects on Epoxy Cure Reactions

Abstract Adherend surface effects on the amine cure of epoxy resins were investivated using finely divided aluminum oxide as high surface area models for aluminum. Calorimetric analysis of simplified crosslinking systems revealed significantly faster reactions which led to lower glass transition temperature materials for activated aluminum oxide filled samples. A monofunctional amine and epoxy were then utilized to obtain soluble reaction products amenable to molecular characterization. These studies similarly showed an increase in the rate of epoxy consumption in the presence of activated aluminum oxide which was attributed to both an increase in the rate of amine addition to epoxy as well as to epoxy homopolymerization. The latter was not observed in the unfilled mixtures. Such changes in reaction mechanism at the adherend surface have implications for the strength and durability of actual adhesive bonds.

Evaluation of supercritical sulfur hexafluoride as a mobile phase for polar and non-polar compounds

The limits in the elution of non-polar and polar compounds with a supercritical sulfur hexafluoride mobile phase are determined. The compatibility of an SF 6 mobile phase with flame ionization detection during pressure programming in capillary supercritical-fluid chromatography is demonstrated. Special modifications to the split injection assembly are described. A decrease in solvent strength with increasing pressure reported in the literature was not observed. As has been indicated in the literature. SF 6 was found to exhibit low solvating power. Normal alkanes up to about n = 30 and polycyclic aromatic hydrocarbons of up to four rings were eluted at 100°C, but no larger compounds of either type. SF 6 has an advantage over CO 2 in that primary amines can be eluted, but it is also limited in most cases to mono-functional amines, and also to mono-functional alcohols and carboxylic acids. No adverse effects on the stationary phase or column deactivation were observed.

The interaction of amines with the occluded state of the Na,K-pump.

We have studied the effect of various amines on the rate of release of 86Rb from the occluded state of dog kidney Na,K-ATPase formed by pre-incubation of the enzyme with 86Rb. In the presence of MgPi, various amines act like K+ or Rb+ in blocking the release of 86Rb from one of two sites for occlusion (the "s" site). Of 38 amines tested, tetrapropylamine and various benzyl amines exhibit the highest affinity; the K1/2 for these compounds is 2-5 mM. In the presence of ATP, when 86Rb is presumably released towards the intracellular face of the pump in the normal mode of operation, 86Rb release is blocked by the presence of amine, but only if the amine is also included in a preincubation with MgPi. The data are consistent with a model in which the interaction of amine with one of the transport sites (the "f" site) prevents the E2----E1 transformation that is stimulated by ATP. When 86Rb deocclusion from the f site has occurred in the presence of amine, the lone 86Rb at the s site can be released in the presence of ATP if the amine is removed from the medium. This suggests that a single 86Rb ion at the s site can be released to the intracellular face of the membrane, and therefore that transport can occur with only one K+ site occupied. The amine that blocks release of one 86Rb ion does not itself become occluded: (a) The interaction of amine and ATP is only seen when both ligands are present in the medium; (b) the effects of amines are not "remembered" after a brief exposure to a rinse medium; (c) with the vanadate-inhibited enzyme, benzyltriethylamine and tetrapropylamine are only weakly effective in blocking 86Rb release from the s site; and (d) organic cations exhibit very low affinity in competition with 86Rb for occlusion at equilibrium. Thus the results are consistent with the idea that monofunctional amines block by binding to the f site but that, unlike K+ and Rb+, they do not become occluded. In contrast, at equilibrium ethylenediamine prevents 86Rb occlusion in a competitive manner, suggesting the possibility of occlusion of the bifunctional amine.

Selected ion monitoring determination of mono- and bifunctional amines by using phosphorus-containing derivatives

Numerous monofunctional amines have been reacted with dimethylthiophosphinic chloride to form stable derivatives. Their good gas chromatographic properties and abundant molecular ions afforded highly sensitive and specific detection by selected ion monitoring (SIM) down to the picogram level. Based upon this derivatization procedure, new methods for the determination of aniline in serum and urine by SIM were developed. The minimum detectable concentration of aniline was 500 pg ml−1. Linear response curves were obtained from 1.5 to 150 ng ml−1 using (2H5)aniline as the internal standard. Specific derivatization of a series of bifunctional amines was achieved with methyldichlorophosphine and sulfur resulting in the formation of stable phospholidine-thiones. These derivatives chromatograph well on nonpolar stationary phases, and their mass spectra exhibit abundant molecular ions. This derivatization reaction was applied to the quantification of ephedrine from urine and serum by SIM with (2H2)ephedrine as the internal standard. The detection limit of the method was 1 ng ml−1. The linearity was established in the range from 10 to 160 ng ml−1.

Inhibition by 3,6-di-tert-butylpyrocatechin in the oxidation of 1-nonene

1. 3,6-Di-tert-butylpyrocatechin (PC) is a more effective inhibitor for the oxidation of 1-nonene than are monofunctional phenols and aromatic amines, or stable 2,2,6,6-tetramethyl-4-benzoylpiperidin-1-oxyl radicals. 2. The high antioxidant activity of PC is due to synergism in the mixtures formed between PC and the 3,6-di-tert-butyl-o-benzoquinone resulting from PC reaction. 3. Rate constants have been determined for the reactions of PC and N-phenyl-N'-naphthyl-o-phenylenediamine with molecular oxygen at 120°C.

Action of p-phenylenediamine derivatives as antioxidants in the oxidation of 1-nonene

1. The p-phenylenediamine derivatives are effective antioxidants for oxidation of 1-nonene, being more active in this respect than either the monofunctional aromatic amines and phenols or the quinones and nitroxylradical alkyl-radical acceptors. 2. In distinction to the monofunctional aromatic amines and phenols, the antioxidant activity of the p-phenylenediamine derivatives increases as the oxygen pressure is reduced. 3. The p-phenylenediamine derivatives do not show synergistic effects when mixed with alkyl-radical acceptors. 4. The inhibiting action of the p-phenylenediamines can be explained by assuming these compounds to form autosynergistic mixtures with their reaction products, quinonediimines, capable of reacting with alkyl radicals.

ChemInform Abstract: HEAT CAPACITY CHANGES IN PROTON ADDITION TO THE NITROGEN OF SATURATED ORGANIC MOLECULES IN WATER. EFFECTS OF SOLVATION

AbstractFür die Aminoalkohole, ‐ether und Diamine (I)‐(VI) wurden die ΔCop‐Werte der Protonierung bei 25 und 40°C bestimmt.

Heat capacity changes in proton addition to the nitrogen of saturated organic molecules in water. Effects of solvation

The ΔC°p values for proton addition to some aminoalcohols, aminoethers and diamines in aqueous solution have been determined at 25 and 40°C, using partial molal heat capacity data for the neutral molecules and their hydrochlorides. A comparison is made between ΔC°p, ΔS° and ΔV° values and the corresponding values for monofunctional amines, and the following features emerge for proton addition to the nitrogen atom of saturated amines in water: (1) Either in mono- or in bifunctional amines the thermodynamic reaction parameters, ΔC°p and ΔS°, change systematically in going from primary, to secondary, to tertiary amines; the same is observed for ΔV°, but only in the case of monofunctional amines. (2) The ΔC°p and ΔS° values of protonation of bifunctional amines are higher than those of monofunctional amines of the same type.Interpretation of this behaviour is made in terms of two concurrent solvation effects: (i) the charged nitrogen–water interaction which is strongly dependent on the number of N-bonded hydrogens; (ii) the hydration of alkyl residues which is less extensive when they are bound to a charged nitrogen than when the nitrogen is neutral.

A method for measuring the internal pH in illuminated chloroplasts based on the stimulation of proton uptake by amines.

A simple method for measuring the internal pH of chloroplasts during steady-state illuminations based on the stimulation of proton uptake by monofunctional amines was developed. Predictions of a mathematical derivation concerning the dependence of the stimulation on the amine concentration, the internal volume, the pK of the amine and the external pH have been verified experimentally. To circumvent uncoupling and swelling due to large internal accumulation of amines extrapolation of the stimulation to low amine concentrations was suggested and shown to lead to valid values. Alternatively, swelling could be largely reduced in a medium containing potassium aspartate and valinomycin.

Chemical Factors Affecting Palmelloid‐Forming Activity of Chloroplatinic Acid on Chlamydomonas eugametos

AbstractIn order to elucidate the physiological mechanism of palmelloid formation of the unicellular green alga Chlamydomonas eugametos by chloroplatinic acid, the factors causing inhibition of the palmelloid formation were studied in various media. Chloroplatinic acid lost its palmelloid‐forming effect in the presence of nitrite ion and amines having a second functional group. Nitrate, potassium, and sodium ions and monofunctional amines were without influence on the effect of chloroplatinic acid. These results indicate that the active form of platinum (IV) may undergo ligand substitution, the resulting complex being unable to cause palmelloid formation.

Epoxy groups responsible for crosslinking in natural rubber

STORAGE hardening in natural rubber, which is of considerable industrial interest, has been ascribed to the crosslinking of carbonyl groups present in the rubber chain1. Supporting evidence is that the crosslinking reaction can be prevented or accelerated by the addition of monofunctional or difunctional amines, respectively. These observations may be explained if the monofunctional amine is regarded as condensing with, and hence destroying, the carbonyl group, whereas the difunctional reagent is capable of reaction with carbonyl groups on separate chains, thus effecting a crosslink. The ability of dimedone (5,5-dimethylcyclohexane-1,3-dione) to inhibit the crosslinking reaction led to the conclusion that the groups were aldehydic1.

Tetracoordination of copper(I) by monofunctional amines

The highest complexes of the monofunctional amines pyridine, quinoline, isoquinoline, piperidine, n- and sec-butylamine, aniline, p-methoxyaniline, and N-benzylidenemethylamine with copper(I) ion in propylene carbonate have been determined by polarography. A maximum coordination of four ligands has been noted in the cases of pyridine and isoquinoline. Solid tetrakis(pyridine)copper(I) percholorate has been isolated, and by infrared examination of 3:1, 4:1, and 5:1 mole-ratio mixtures of the monofunctional amines with tetrakis(acetonitrile)copper(I) perchlorate, the tetracoordination of quinoline, isoquinoline, piperidine, and N-benzylidenemethylamine to copper(I) has been established. The polarographic data have been used to estimate the appropriate overall stability constants in propylene carbonate.