Primary Amine Function Research Articles

Role of the kinetic template effect in the syntheses of non symmetric Schiff base complexes

The template effect involves two main effects, first the “kinetic template effect”, in which a metal ion is able to hold two reactive functions in a position that allows a reaction to occur, followed by the “thermodynamic template effect” that favours the formation of a thermodynamically more stable product resulting from the reaction. Through the preparation of a non symmetric Schiff base, we highlight the primordial role of the “kinetic template effect”. Very often, this kinetic effect is not easy to evidence, the resulting complex being too reactive to be isolated. In the present example, the use of an ambidentate ligand, pyrrole carboxaldehyde, has been quite interesting. Reaction of a cationic copper complex possessing a primary amine function coordinated to the copper ion with pyrrole carboxaldehyde can yield two different complexes, depending on the reaction conditions. In absence of a base, the structural determination shows that the copper ion is linked in apical position to the carbonyl oxygen atom of pyrrole carboxaldehyde and the two reactive aldehyde and amine functions are unable to react, as a consequence of their mutual coordination to copper. On the contrary, addition of a base to the reaction mixture induces deprotonation of the pyrrole function followed by its coordination to copper ion, leaving free the carbonyl carbon atom that can be positioned in the vicinity of the primary amine function, thus facilitating the formation of a new imine function. The resulting thermodynamically stable complex is characterized by X-ray diffraction.

Magnetic ordering of NiII4 Cubane complexes through hydrogen bonds

Abstract The serendipity synthesis of the 2-hydroxy-3-methoxy-benzaldehyde or o-vanillin nickel(II) cubane complex, obtained by ourselves and other workers, can be rationalized to give the cubane in a high yield by direct use of 2-hydroxy-3-methoxy-benzaldehyde (H-ovan). The structural determinations of crystals obtained according to the two experimental processes show that the complex formulated [(MeOH)Ni(μ3-OMe)(ovan)]4 (ovan = deprotonated form of o-vanillin) is characterized in the two cases. Ni-Ni ferromagnetic interactions (JNiNi = 5.8 cm−1) giving an S = 4 ground state are active in the Ni4 cubane. Replacement of methanol molecules coordinated to the Ni ions by a diol, an amino-alcohol or an amino-ether allows self-association of these Ni4 units according to two different ways: by direct coordination bonds through the diol ligand or by hydrogen bonds involving the OMe groups of o-vanillin located at the periphery of the cubane and the hydrogen atoms of the primary amine functions. This association is suggested in the two cases by the presence of out-of-phase signals (χ”) when ac susceptibility measurements are performed at different frequencies. These molecules do not behave as SMM for these χ” signals, that are not frequency-dependent, correspond to the establishment of a three-dimensional ordering.

GROWTH OF POLYELECTROLYTE ON LIGNOCELLULOSIC FIBRES: STUDY BY ZETA POTENTIAL, FTIR, AND XPS

A layer-by-layer (LbL) self-assembly technique using polyallylamine hydrochloride (PAH) and polyacrylic acid (PAA) was employed to build up polyelectrolyte multi-layers on pretreated thermomechanical pulp fibres. These pretreated fibres previously had been oxidized by means of a 4-acetamido TEMPO-mediated process in order to create carboxylic functions. These allow the subsequent formation of amide bonds between PAH and fibres. X-ray photo-electronic spectroscopy (XPS) analyses confirmed the formation of amide bonds between the carboxylic function on the fibres and the primary amine function of the PAH. Besides, the surface charge intensity of the coated fibres was determined by measuring the zeta potential after each treatment step.

Selective Grafting of Primary Amines onto Carbon Nanotubes via Free-Radical Treatment in Microwave Plasma Post-Discharge

A novel strategy to graft functional groups at the surface of carbon nanotubes (CNTs) is discussed. Aiming at grafting nitrogen containing groups, and more specifically primary amine covalent functionalization, CNTs were exposed under atomic nitrogen flow arising from an Ar + N2 microwave plasma. The primary amine functions were identified and quantified through chemical derivatization with 4-(trifluoromethyl)benzaldehyde and characterized through X-ray photoelectron spectroscopy. The increase of the selectivity in the primary amines grafting onto CNTs, up to 66.7% for treatment of CNT powder, was performed via the reduction of post-treatment oxygen contamination and the addition of hydrogen in the experimental set-up, more particularly in the plasma post-discharge chamber. The analyses of nitrogenated and primary amine functions grafting on the CNT surface suggest that atomic nitrogen (N•) and reduced nitrogen species (NH• and NH2•) react preferentially with defect sites of CNTs and, then, only atomic nitrogen continues to react on the CNT surface, creating defects.

ChemInform Abstract: Chiral Amine Organocatalysts for the syn‐Aldol Reaction Involving Substituted Benzaldehydes and Hydroxyacetone.

Abstract A new series of cyclohexanediamine organocatalysts that contain the primary amine functionality has been designed, synthesized and tested as catalysts for the asymmetric aldol reaction involving hydroxyacetone and a variety of substituted benzaldehydes. High enantioselectivites and diasteroselectivites were obtained using catalyst 1a for these reactions. A key step in this reaction for the formation of the syn -product is the formation of a stable intramolecular hydrogen bonded Z -enamine isomer, which in addition to the steric bulk of the catalyst, serve to dictate the course of the stereochemical outcome of the reaction.

Ammonia Plasma Treated Polyethylene Films for Adsorption or Covalent Immobilization of Trypsin: Quantitative Correlation between X-ray Photoelectron Spectroscopy Data and Enzyme Activity

The ammonia plasma process was used for generating reactive groups, particularly primary amine functions on the surface of polyethylene (PE) films, to immobilize the enzyme trypsin. The attachment of the enzyme was achieved by directly applying an aqueous solution of trypsin to the plasma-activated surface or by using glutaraldehyde as a chemical linker. In both cases, the utilization of sodium cyanoborohydride efficiently stabilized the immobilization. The surfaces were analyzed by X-ray photoelectron spectroscopy (XPS) and enzymatic activity measurements. Active trypsin was successfully immobilized on the surface with a mean activity of 0.09 ± 0.02 U/cm(2). The study of the stability of the immobilized enzyme during repetitive assays showed that some activity could be maintained during several months. An original quantitative correlation between the immobilized enzyme activity and the XPS signal intensity of the S 2p electrons present in the sulfur-containing amino acid residues was evidenced.

Enantio- and Diastereoselective Aldol Reaction of Thioamides

The authors disclose a copper(I)-catalyzed enantio- and diastereoselective aldol ­reaction of thioamides and aldehydes. Although there has been considerable interest from the synthetic community in the field of direct catalytic asymmetric aldol methodology, to date there have been a limited number of publications utilizing aldol donors in the carboxylic acid oxidation state. The authors demonstrate the synthetic utility of their products by converting the thioamide moiety into an aldehyde, ketone, 1,3-dicarbonyl, amide or a primary amine functionality.

Chiral amine organocatalysts for the syn-aldol reaction involving substituted benzaldehydes and hydroxyacetone

A new series of cyclohexanediamine organocatalysts that contain the primary amine functionality has been designed, synthesized and tested as catalysts for the asymmetric aldol reaction involving hydroxyacetone and a variety of substituted benzaldehydes. High enantioselectivites and diasteroselectivites were obtained using catalyst 1a for these reactions. A key step in this reaction for the formation of the syn-product is the formation of a stable intramolecular hydrogen bonded Z-enamine isomer, which in addition to the steric bulk of the catalyst, serve to dictate the course of the stereochemical outcome of the reaction.

Amino Disiloxanes for CO2 Capture

A series of aminodisiloxanes were synthesized with varying degrees of functionality and steric hindrance and screened as CO2-capture solvents. Compounds with unhindered primary amine groups were found to come closest to reaching their theoretical CO2 uptake values. In contrast, materials containing either hindered primary amines or secondary amine functionality were less efficient. Addition of a cosolvent, triethylene glycol, was found in most cases to maintain solution liquidity and thereby minimize mass transfer limitations on exposure to CO2.

Thin and Robust Encapsulation of Silver and Gold Nanoparticles with Dithiocarbamate-anchored Polyelectrolytes

ABSTRACTA robust, stable and thin primary amine functionalization is applied to gold and silver nanoparticles from poly(allylamine hydrochloride) (PAH) by converting a fraction of the amine groups in the polymer to dithiocarbamate (DTC) ligands, which absorb strongly onto noble metal surfaces. We observe marked improvements in the properties of gold nanospheres with a DTC-anchored rather than physisorbed PAH cap. The same level of improvement is not seen in silver nanoparticles, although it is clear from a distinct change in the plasmon spectrum in silver nanocubes that the DTC ligand does interact with the silver surface. In spite of their amine functionalization, both silver and gold particles show low cytotoxicity, possibly due to absorption of serum proteins forming a protective coating on the positively charged particle surface.

Bifunctional Catalysts for Asymmetric Nazarov Cyclizations

An organocatalytic asymmetric Nazarov cyclization is presented. The catalyst, a bifunctional structure with a thiourea moiety, and a primary amine function is suggested to activate the substrate by a double hydrogen-bonding ­interaction (eq. a). Although the reaction proved to be slow, the provided products, containing all-­carbon quaternary stereocenters, were synthesized in high yields and enantioselectivities. It would be interesting to speculate a mechanism involving truly covalent enamine and iminium intermediates, as such providing an explanation for the low turnover due to product inhibition (eq. b).

Catalytic Use of a Soluble Organoindium(III) Species for Allylation and Crotylation of Ketones with Boronates

AbstractThe unprecedented use of a soluble organoindium species, indium(III) hexamethyldisilazide [In(III)(hmds)3], for catalytic carboncarbon bond formations between ketones and boronates, is reported. Various functionalized tertiary homoallyl alcohols were generated easily in high yields. Remarkably, free hydroxy and primary amine functionalities proved to be tolerated. A rate acceleration and markedly improved diastereoselectivities were observed in the presence of methanol. Based on preliminary NMR experiments and the α‐selectivity with an α‐substituted boronate, we assume the in situ generation of reactive allylindium(III) species through catalytic boron‐to‐indium transmetalation.

Gas-Phase Bioconjugation of Peptides via Ion/Ion Charge Inversion: Schiff Base Formation on the Conversion of Cations to Anions

The selective covalent modification of singly protonated peptides in the gas-phase via ion/ion charge inversion reactions is demonstrated. Doubly deprotonated 4-formyl-1,3-benzene disulfonic acid serves as a reagent anion for forming a Schiff base via the reaction of a primary amine on the peptide and the aldehyde functionality of the reagent anion. The process is initiated by the formation of an ion/ion complex comprised of the two reactants. Ion trap collisional activation of the complex results in loss of water from the intermediate that gives rise to Schiff base formation. N-terminally acetylated peptides with no lysine residues do not undergo covalent bond formation upon reaction with the reagent anion. Rather, the adduct species simply loses the reagent either as a neutral species or as a deprotonated species. The ability to modify singly protonated peptide ions covalently and selectively opens up new possibilities for the analysis of peptides and, possibly, other analyte species with primary amine functionalities.

Bioengineering of stainless steel surface by covalent immobilization of enzymes. Physical characterization and interfacial enzymatic activity

Two hydrolytic enzymes, namely lysozyme and trypsin, were covalently immobilized onto stainless steel surfaces using wet chemistry processes. The immobilization strategy took advantage of the spontaneous physisorption of the polymer poly(ethylene imine) (PEI) onto stainless steel to yield a firmly attached, thin organic layer containing a high density of primary amine functions. Both enzymes were then covalently grafted to the surface via a glutaraldehyde cross-linker. Alternatively, a thicker underlayer of PEI was chemisorbed by cross-linking two PEI layers by glutaraldehyde. The effective presence of both enzymes on the stainless steel surfaces and their relative amount were assessed by immunochemical assays employing specific anti-enzyme antibodies. Eventually, the hydrolytic activity of the immobilized enzymes was evaluated by local enzymatic tests with suitable substrates. This work demonstrates that, although the amount of enzymes did not vary significantly with the underlayer thickness, their hydrolytic activity could be much improved by increasing the distance from the oxide surface and, likely, by favoring their accessibility. Our data suggest that the immobilization of enzymes on solid oxide surfaces is feasible and efficient, and that the enzymes retain catalytic activity. It may thus provide a promising route towards biofilm-resistant materials.

Combined Continuous Wave and Pulsed Plasma Modes: For More Stable Interfaces with Higher Functionality on Metal and Semiconductor Surfaces

AbstractA novel approach to producing improved bio‐interfaces by combining continuous wave (CW) and pulsed plasma polymerization (PP) modes is reported. This approach has enabled the generation of stable interfaces with a higher density of primary amine functionality on metal, ceramic and semiconductor surfaces. Heptylamine (HA) was used as the amine‐precursor. In this new design, a thin CW PPHA layer is introduced to provide strong cross‐linking and attachment to the metal or semiconductor surfaces and to provide a good foundation for better bonding a pulsed PPHA layer with high retention of functional groups. The combined mode provides the pulsed mode advantage of a 3‐fold higher density of primary amines, while retaining much of the markedly higher stability in aqueous solutions of the continuous mode.magnified image

Very short functionalized carbon nanotubes for membrane applications

The cutting and functionalization of carbon nanotubes is described, applying a single-step ball-mill based process. Very short carbon nanotubes bearing primary amine functions were produced, characterized and incorporated in polymeric membranes. The gas separation performance of the composite membranes was tested.

Hypergolic Reactions of TNT

AbstractOne way being considered to destroy trinitrotoluene (TNT) land or surf mines is to exploit its reactivity using darts containing chemicals, which, upon contact with TNT, cause instantaneous decomposition, but not detonation. To determine the best candidates to fill the darts, liquids, specifically amines, which react in a hypergolic fashion with TNT were examined for both the rate of reaction and amount of energy released. Micro‐calorimetry was used to measure heat release while spectroscopy and conventional peak intensity monitoring by chromatography were used to examine the rate of reaction. Calorimetry measurements showed little variation between different amines reacting with TNT (about 110–130 kJ mol−1 TNT). TNT reaction with hydride actually produced more heat than with amines. Further, dinitrotoluene (DNT), which generates substantial heat, did not undergo a hypergolic reaction with amines suggesting that heat release is not the controlling factor for the hypergolic reactions. Rate constants, determined for the loss of TNT in dilute acetonitrile solution, clearly showed distinctions among the amines. The more primary amine functionalities in the amine compound, the faster it destroyed TNT. Hydrides or amine mixtures spiked with hydride decomposed substantially faster than the amines alone. However, a direct correlation between reaction rate and time‐to‐ignition was not observed.

Controlled Amine Functionalization and Hydrophilicity of a Poly(lactic acid) Fabric

AbstractThe surface of PLA fabric has been successfully modified by pulsed plasma polymerization of heptylamine (PPHA) giving increased hydrophilicity and achieving a sufficient level of primary amine functionality (3.5%) for practical application in biotechnology. This is the first report that the density of primary amine (–NH2) in PPHA, quantified by chemical derivatization, can be controlled by selection of pulsed plasma conditions. The duty cycle and the average RF power were the key parameters for achieving both a higher density of primary amine and increased hydrophilicity.magnified image

Synthesis of Amphiphilic Supramolecular Miktoarm Star Copolymers by Molecular Recognition

Synthesis of novel amphiphilic supramolecular miktoarm star copolymers has been achieved through complementary molecular recognition and interactions between carboxy groups and amino groups. Polystyrenes carrying two and one carboxy groups at the middle of the polymer chain are used as precursors to react with poly(ethylene oxide) (PEO) end-capped with a primary amine functionality (-NH(2) ) or a quaternary ammonium hydroxide functionality (-N(+) (CH(2) CH(3) )(3) OH(-) ). The result suggests that the basicity of the amine plays a key role in the molecular recognition procedure. The efficiency of ionic bond formation can be enhanced from 40% up to 97% by using PEO-N(+) (CH(2) CH(3) )(3) OH(-) instead of PEO-NH(2) . The obtained supramolecular polymers can be dissociated in dilute acid solution at room temperature.

Poly(ethylene glycol)-Based Stable Isotope Labeling Reagents for the Quantitative Analysis of Low Molecular Weight Metabolites by LC−MS

Stable isotope labeling (SIL) in combination with liquid chromatography-mass spectrometry is one of the most widely used quantitative analytical methods due to its sensitivity and ability to deal with extremely complex biological samples. However, SIL methods for metabolite analysis are still often limited in terms of multiplexing, the chromatographic properties of the derivatized analytes, or their ionization efficiency. Here we describe a new family of reagents for the SIL of primary amine-containing compounds based on pentafluorophenyl-activated esters of 13C-containing poly(ethylene glycol) chains (PEG) that addresses these shortcomings. A sequential buildup of the PEG chain allowed the introduction of various numbers of 13C atoms opening extended multiplexing possibilities. The PEG derivatives of rather hydrophilic molecules such as amino acids and glutathione were successfully retained on a standard C18 reversed-phase column, and their identification was facilitated based on m/z values and retention times using extracted ion chromatograms. The mass increase due to PEG derivatization moved low molecular weight metabolite signals out of the often noisy, low m/z region of the mass spectra, which resulted in enhanced overall sensitivity and selectivity. Furthermore, elution at increased retention times resulted in efficient electrospray ionization due to the higher acetonitrile content in the mobile phase. The method was successfully applied to the quantification of intracellular amino acids and glutathione in a cellular model of human lung epithelium exposed to cigarette smoke-induced oxidative stress. It was shown that the concentration of most amino acids increased upon exposure of A549 cells to gas-phase cigarette smoke with respect to air control and cigarette smoke extract and that free thiol-containing species (e.g., glutathione) decreased although disulfide bond formation was not increased. These labeling reagents should also prove useful for the labeling of peptides and other compounds containing primary amine functionalities.