Primary Amide Group Research Articles

Nanocomposite films based on chitosan–poly(vinyl alcohol) and silver nanoparticles with high antibacterial and antioxidant activities

Abstract The present study focused on the synthesis of chitosan–silver nanocomposite films (CSNFs) due to their potential application in various domains including wound dressing, packaging and water purification. Silver nanoparticles (Ag NPs) were generated in-situ by using UV-irradiation and chitosan (CS) as both reductant and stabilizer. FTIR spectra revealed that the primary amine and amide groups of chitosan have specific interactions with nanoparticles surface. The diameter of AgNPs ranged from 170 to 200 nm as determined by DLS and TEM observation. Furthermore, CSNFs were tested for their biological activities and results showed higher antioxidant and antibacterial activities than chitosan film, which increased with AgNPs amount, suggesting that surface structures of chitosan strongly influence the adsorption of AgNPs and the antimicrobial activities. These observations indicate that nanocomposite films have potential applications as anti-infectious wound dressing. Many studies reported the toxicity of AgNPs and their health and environmental risks. For that purpose, cytotoxicity of CS–AgNPs was performed by MTT assay on Chinese hamster ovary R(CHO-K1) cell lines. Results showed that CS–AgNPs have no-cytotoxicity effect, which suggests the possibility of CS–AgNPs uses in foods and biomedical applications.

Synthesis, characterization and antibacterial study on the chitosan-functionalized Ag nanoparticles

This study provided a facile, one-step hydrothermal method to synthesize stable Ag colloid in aqueous solution by utilizing chitosan as both reductant and stabilizer. The formation of chitosan-functionalized Ag nanoparticles was verified by UV–Vis, FTIR, TEM, AFM and XRD measurements. FTIR results revealed that the primary amine groups and amide groups of chitosan have specific interactions with the surface of Ag nanoparticles. The average diameter of the Ag nanoparticles is 10.0±5.4nm as determined by TEM. Ag nanoparticles are highly crystalline as revealed by HR-TEM and XRD measurements. The size and shape of Ag nanoparticles are also found to depend on the pH condition in the synthesis. Ag nanoparticles were the main products at pH5.0 whereas large Ag nanotriangle and truncated triangular nanoplate were dominant at pH4.0 in the synthesis. Due to its monodispersity and good stability, the chitosan-functionalized Ag colloid synthesized at pH5.0 was further tested for its antibacterial activities against gram-positive bacteria, gram-negative bacteria and fungus. The results of zone of inhibition, inhibition ratio and SEM characterization revealed that chitosan-functionalized Ag nanoparticles have great bactericidal efficiency against both bacteria and fungus.

An exploration into the amide–pseudo amide hydrogen bonding synthon between a new coformer with two primary amide groups and theophylline

Double the FUN! A rare amide–pseudo amide hydrogen bonding synthon has been established for the co-crystal between a new coformer with two primary amide groups and theophylline.

1-Methoxypyrrole-2-carboxamide-A new pyrrole compound isolated from Streptomyces griseocarneus SWW368.

A new pyrrole compound, 1-methoxypyrrole-2-carboxamide, was obtained from a culture broth of Streptomyces griseocarneus SWW368, which was isolated from the rhizospheric soil under a Para rubber tree (Hevea brasiliensis). The chemical structure was elucidated by 1D NMR, 2D NMR, and MS, as a pyrrole ring with a N-methoxy group and a primary amide group. It exhibited antibacterial properties against Kocuria rhizophila, Staphylococcus aureus and Xanthomonas campestris pv. oryzae; however, cytotoxicity of the compound at 714 μM against several mammalian tumor cell lines, i.e. A549, PANC1, HT29, HT1299 and HeLa S3, were not detected.

ChemInform Abstract: Nickel‐Catalyzed Negishi Cross‐Coupling of Bromodifluoroacetamides.

AbstractAn efficient transformation of bromodifluoroacetamides containing cyclic and a primary, secondary or tertiary amide group, including cyclic and amino acid derived moieties, with variously functionalized aryl zinc reagents is described.

Hydrogen-bond networks in polymorphs and solvates of metallorganic complexes containing ruthenium and aminoamide ligands

The hydrogen-bond networks of half-sandwich Ru(ii) complexes containing primary and secondary amide groups are described together with their guest inclusion properties.

Non-radiative relaxation of UV photoexcited phenylalanine residues: probing the role of conical intersections by chemical substitution

A conformation-selective photophysics study in phenylalanine model peptides, combining pump-probe gas phase experiments and excited state calculations, highlights for the first time the quenching properties of a primary amide group (through its nπ* excited state) along with the effect of vibrational energy that facilitates access to the conical intersection area.

Hydrogen bonding in crystal forms of primary amide functionalised glucose and cellobiose

A glucoside and cellobioside of glycolamide were synthesised and the crystal chemistry of these compounds investigated. The amidoglucoside crystallised in the P21 space group. The primary amide group participates in C(7) and C(17) chains also involving the pyranose oxygen and hydroxyl groups. The amidocellobioside crystallised as a methanol solvate in the P21 space group. The amide N–H groups donate hydrogen bonds to oxygen atoms on the cellobiose units, while intramolecular hydrogen bonds give rise to S(7) and S(9) motifs in addition to a R33 (9) motif. A tetra-O-acetylglucoside derivative of thioglycolamide and its sulfoxide derivative were synthesised to examine the effect of protecting the glucopyranose hydroxyl groups. The thioglycolamido derivative, which crystallised in the P212121 space group, featured amide N–H groups donating to the glucopyranose oxygen and an acetyloxy group. The sulfoxy derivative crystallised in the P21 space group and featured the primary amide groups forming R23(8) motifs generating a 21 ladder.

Synthesis of 2-aryl-6H,7H-[1,3]oxazolo[5,4-d]pyrimidine-7-thione and 2-aryl-6H,7H-[1,3]thiazolo[5,4-d]pyrimidine-7-thione using 2-aroylaminomalonodiamide

There are two strategic approaches to construct the azolopyrimidine system: via cyclization of the pyrimidine ring on an azole or by fusion of azole ring with the pyrimidine. In this work we used two approaches using 2-aroylaminomalonodiamides Ia–Ic as the starting materials [5]. In this case, the target products were 2-aryl-6H,7H-[1,3]oxazolo[5,4-d]pyrimidine-7-thiones Va–Vc and 2-aryl-6H,7H-[1,3]thiazolo[5,4-d]pyrimidine-7-thiones VIa–VIc. The reactions sequence I→II→IV→V has as the initial reaction that of 2-aroylaminomalonodiamides Ia–Ic with ethyl formate in the presence of sodium ethoxide to form 5-aroylamino-6-hydroxypyrimidin-4-ones IIa– IIc. The C NMR spectra of these compounds contain the characteristic signals of the C and C atoms of the pyrimidine ring in the ranges of 102.87–103.34 and 165.75–165.85 ppm, respectively. In the H NMR spectra there are no signals of the primary amide groups, and the singlet of СH proton appears in the range of 8.04–8.07 ppm.

Role of non-covalent interactions in the molecular organization of N-n-hexadecanoyl amino acid amphiphiles with hydrophobic Cα-side chains in Tris buffer (pH 9.3)

Role of non-covalent interactions on the molecular packing of N-n-hexadecanoyl amino acid amphiphiles (NHAA) has been studied using a set of corresponding L-amino acid (glycine, alanine, valine, proline and phenylalanine) derivatives in 50mM Tris buffer at pH 9.3. Self-assembly properties in aqueous dispersion were characterized by various physical techniques like tensiometry, fluorimetry, UV–vis spectroscopy, circular dichroism (CD) and differential scanning calorimetry (DSC). The results reveal that the hydrophobic interaction plays the driving role for such self assembly phenomena which is synergistically influenced by additional non-covalent interactions among the surfactants arising from the amino acid units present on the molecular backbone. Despite major similarities in structural elements (except their Cα-side chain residues) among all the NHAA amphiphiles described here, three issues were found to be important towards their self assembly properties viz, (a) optimal intermolecular distance that arises from van der Waals repulsions of the side chain residues and the electrostatic repulsions among anionic head groups; (b) intermolecular H-bonding and π–π type attractive interaction that reduces the intermolecular distance and (c) the effective solvation of the head groups required for the self assembly. Since, primary amide group is ubiquitous for all the amphiphiles except NHPro, the strength of H-bonding interaction among the amphiphiles was also investigated and found to be affected by the nature of the Cα-side chain residues. NHPhe was found to be unique compared to others due to the π–π type attractive interaction operative at the aromatic Cα-side chain while for others, the repulsive interactions among the Cα-side chain residues make them behave differently. Optimized non-covalent interactions with requisite solvation of the head group, molecular packing was found to be better for NHAla, while such packing was affected by van der Waals repulsion among the bulky Cα substituents (e.g. isopropyl group for NHVal) or stabilized by π–π interaction (for NHPhe) and intermolecular H-bonding interaction via amide linkages. The self-assembly behavior was found to be complex for proline based system (NHPro) where the hydrophobic effect and the steric disposition of the cyclic side chain significantly influence its molecular packing as well as its other self assembly properties. The characterization of thermodynamic parameters reveals that the hydrophobicity of Cα-substituents lowers the free energy of micellization. The DSC studies show that Krafft Temperature and enthalpy of solution were affected by the nature of the Cα-substituents. The van der Waals repulsion among the bulky substituents increases the intermolecular separation reducing the strength of the molecular packing as well as the aggregation number. An invariant CD signature for NHPhe at its non aggregated and aggregated state indicates a unique non-chiral self assembly and a new π–π dimeric molecular organization model for NHPhe amphiphiles has been proposed to rationalize this behavior.

3-Hydroxy-2-methoxybenzamide

The crystal structure of the title compound, C8H9NO3, features centrosymmetric dimers with two amide groups inter­connected by a pair of almost linear N—H⋯O hydrogen bonds. Through inter­molecular O—H⋯O inter­actions between phenolic hy­droxy groups and carbonyl O atoms, these dimers are assembled into undulating hydrogen-bonded layers parallel to the [101] plane. Additionally, the anti-H(—N) atom of the primary amide group forms an intra­molecular hydrogen bond to the O atom of the meth­oxy group. The amide group froms a dihedral angle of 12.6 (1)° with the phenyl ring.

ChemInform Abstract: Transamidation of Primary Amides with Amines Using Hydroxylamine Hydrochloride as an Inorganic Catalyst.

Metal-free catalysis: A method for the transamidation of primary amides with primary or secondary amines provides access to secondary and tertiary amides, by utilizing catalytic quantities of hydroxylamine hydrochloride to activate the chemically robust primary amide group (see scheme). A mechanism of primary amide activation through a hydrogen-bonding complex is proposed.

Hyperbranched poly(amidoamine)/polysulfone composite membranes for Cd(II) removal from water

A composite membrane composed of hyperbranched poly(amidoamine) (HYPAM) and polysulfone (PSf) was successfully prepared to enable the removal of heavy metal ions from contaminated aqueous media. HYPAM was prepared by a one-pot reaction followed by modification with palmitoyl chloride, which included a long aliphatic chain that improved the compatibility with the hydrophobic PSf. The dendritic chelating agent HYPAM was incorporated into PSf via a phase inversion process to produce a HYPAM/PSf membrane. The resulting membrane was characterized by thermogravimetric analysis, X-ray photoelectron spectroscopy, attenuated total reflection Fourier transform infrared spectroscopy, and field-emission scanning electron microscopy. The binding capacity of the HYPAM/PSf membrane toward heavy metal ions [Cd(II)] was investigated by inductively coupled plasma atomic emission spectroscopy. The efficiency of Cd(II) removal was 51% and resulted from metal ion complexation by a tertiary amine of HYPAM, and primary amine and amide groups grafted onto the PSf membrane surface. Moreover, the water permeability and the bovine serum albumin (BSA) retention of the HYPAM/PSf composite membrane were as high as 18Lm−2h−1 at 1bar and 85%, respectively. Under acidic conditions, the composite membrane recovered 86% of the Cd(II) ions. The findings of the present study highlight the potential for using HYPAM/PSf composite membranes as effective recyclable materials for the removal of heavy metal ions in the context of water treatment.

Synthesis of PMMA-co-PMAA Copolymer Brush on Multi-Wall Carbon Nanotubes

Poly(methyl methacrylate)/poly(methacrylamide) copolymer (PMMA-co-PMAA) was synthesized by a free radical copolymerization of MMA and MAA monomers in methylethyl ketone using AIBN as radical initiator. Multi-wall carbon nanotubes (MWCNT) were oxidized in KMnO4 acidic suspension. Carboxyl groups on the surface oxidized MWCNT were reacted with primary amide group of PMMA-co-PMAA copolymer in MEK solution under ultrasound to form polymer brush on the surface of MWCNT. With the help of TG analyses the amount of covalently grafted PMMA-co-PMAA copolymer onto MWCNT surface was determined as ?47 wt%. TEM analyses identified thin co-polymer layer adhered onto MWCNT surface with average thickness ?5 nm.

Transamidation of Primary Amides with Amines Using Hydroxylamine Hydrochloride as an Inorganic Catalyst

Metal-free catalysis: A method for the transamidation of primary amides with primary or secondary amines provides access to secondary and tertiary amides, by utilizing catalytic quantities of hydroxylamine hydrochloride to activate the chemically robust primary amide group (see scheme). A mechanism of primary amide activation through a hydrogen-bonding complex is proposed.

X-ray photoelectron spectroscopy analysis on surface modification of Konjac glucomannan membrane by nitrogen plasma treatment

► The nitrogen plasma modification of Konjac glucomannan was carried out using ion beam injection machine. ► The surface atomic composition was evaluated by X-ray photoelectron spectroscopy analysis afterward. ► Atomic concentration ratio of wO/wC increased using plasma treatment. ► The molecular chain degraded and acetyl was partly removed. Hydroxyl was partly replaced by primary amide group. In order to improve the surface property of Konjac glucomannan (KGM) film, the nitrogen plasma modification was carried out using ion beam injection machine. The surface atomic composition was evaluated by X-ray photoelectron spectroscopy analysis afterward. It was observed that the atomic concentration ratio of wO/wC increased using plasma treatment. The molecular chain degraded and acetyl was partly removed. Hydroxyl was partly replaced by primary amide group. Generation of new functionality groups suggested that plasma treatment might be an effective means to modify the physical property of KGM film.

라카제를 이용한 폴리아미드 섬유의 효소 가공

This study is to optimize the conditions for the treatment of polyamide fabrics using laccase. The pH, temperature, treatment time, and concentration were varied; their effects were evaluated by measuring the number of primary amide groups by the uptake of an acid dye measured by K/S of dyed polyamide fibers. The hydrophilicity of the fabrics was evaluated in terms of moisture regain and wettability. The effects of the mediator, ABTS, on the laccase activity were also evaluated. The optimal treatment conditions were identified as a pH of 4.5, temperature of , treatment time of 6 hours, and concentration of 10% of the weight of the fabric (o.w.f.). ABTS facilitated the activity of laccase on the polyamide fabrics. Voids and cracks on the surfaces of the laccase-treated polyamide fabrics were responsible for improved wettability. The results proved that laccase treatment improved the hydrophilicity of polyamide fibers without decreasing their strength.

ChemInform Abstract: Hydrosiloxane—Ti(OiPr)4: An Efficient System for the Reduction of Primary Amides into Primary Amines as Their Hydrochloride Salts.

A simple and useful method for the reduction of primary amides into the corresponding amines using a polymethylhydrosiloxane (PMHS)–Ti(OiPr)4 reducing system is described. Aromatic as well as aliphatic primary amides are reduced in high selectivity and excellent yields. The reduction could proceed via dehydration of the primary amide group into the corresponding nitrile which is then reduced into the corresponding primary amine.

Difference between 1H NMR signals of primary amide protons as a simple spectral index of the amide intramolecular hydrogen bond strength

The effect of the intramolecular H‐bonding of the primary amide group on the spectral properties and reactivity of this group towards electrophiles has been studied in systematic rows of 1,2,5,6,7,8‐hexahydro‐7,7‐dimethyl‐2,5‐dioxo‐1‐R‐quinoline‐3‐carboxamides and 2‐aryliminocoumarin‐3‐carboxamides using 1H and 15N NMR spectroscopy and the kinetics of model reactions. The upfield signal of the amide proton that is not intramolecularly H‐bonded (Ha) depends on external factors such as solvent nature and concentration. At the same time, the downfield chemical shift of the Hb proton (bonded by the intramolecular hydrogen bond) depends mostly on the strength of the intramolecular H‐bond, which is affected by such internal factor as electron nature of substituent R. The substituent's influence on the Hb proton's chemical shift is more effective in deuterochloroform medium than in DMSO‐d6 where the intramolecular hydrogen bond is less stable. The value Δδ(H) = δ(Hb) − δ(Ha) is suggested as a simple comparative spectral index of the intramolecular hydrogen bond strength in these and similar compounds. By contrast, the effect of R on the 15N NMR chemical shift of the amide nitrogen has turned out to be too small to estimate changes of the electron density at the nitrogen. The effect of the intramolecular H‐bond on the reactivity of the amide group is twofold. When the cleavage of the H‐bond occurs on the rate limiting step it dramatically reduces the reaction rate. In the other case, the strengthening of the H‐bond favors the reaction rate because of the increase of the electron density at the amide nitrogen. Copyright © 2011 John Wiley & Sons, Ltd.

Palladium-Catalyzed Approach to Primary Amides Using Nongaseous Precursors

A simple protocol is reported for the preparation of primary aryl amides under Pd-catalyzed carbonylation chemistry applying a two-chamber system with crystalline and nontransition metal based sources of carbon monoxide and ammonia. The method is suitable for the synthesis of a number of primary amides with good functional group tolerance. Incorporation of (13)CO into the primary amide group was also found to be effective making this approach useful for accessing carbon isotope labeled derivatives.