Action mechanism of antioxidation and anticorrosion and molecular design for perfluoropolyether fluid additives (I) --Action mechanism of additive and property of donating-accepting electron

The combination energy and chemical adsorption energy of N-substituted perfluoropoly- alkyletherphenylamide (PFPEA) additive to perfluoropolyalkylether oxygen radical (RfO.) and to Fe atom have been calculated by quantum chemical methods. Structural characteristics, action mechanism, property of donating-accepting electron and substituent effect for antioxidant and anticorrosive additive are investigated. It is found that HOMO of the additives is a p-molecular orbital with lone pair electron of heteroatom. The HOMO of PFPEA additive reacts with LUMO of Fe atom to result in chemical adsorption. The LUMO of additive can interact with the SOMO of RfO. and accept electron of RfO. to form stable addition product. The additives have the property of donating-accepting electron. The electron-releasing group, particularly, the phenyl group, introduced to N atom of phenylamide can increase the combination energy and chemical adsorption energy, and enhance the antioxidant and anticorrosive efficiency. The research achievements can provide useful information for the designing of new antioxidant and anticorrosive additive. Based on the calculated results, antioxidant and anticorrosive efficiency can be predicted roughly as the following order: compounds III＞II＞I＞IV＞V.     

Action mechanism of antioxidation and anticorrosion and molecular design for perfluoropolyether fluid additives (II)

Three kinds of the antioxidation and anticorrosion additives from the N-substituted perfluoropolyalkylether phenylamide (PFPEA) were selected and synthesized. UV and IR spectral analyses were carried out, and strong absorption peaks of UV from benzene ring are about 240.7, 215.4 and 230.1 nm, respectively. The characteristic peaks of IR from the C=O are about 1713.9, 1712.2 and 1710.8 cm^-1, respectively. The antioxidant and anticorrosive property was tested for the three synthesized additives. The results show that the weight loss of lubrication oil can decrease by 1/7, 1/9 and 1/25 respectively after adding synthesized additives. The thermal decomposition temperature(T_D) in the presence of Al₂O₃ can increase by 19–22°C. From theoretic and experimental study it indicates that the PFPEAs with nitrogen heteroatom not only accepts electron from perfluoropolyalkylether oxygen radical (R_fO.) to form a stable adduct and to prevent RfO. decomposing further, but also donates electron to form chemical adsorption film and to protect metal from corrosion. These additives have shown the better property of the antioxidation and anticorrosion. An electron-releasing group, or phenyl group, introduced to the N-atom of this kind of compound can improve the antioxidant and anticorrosive efficiency of the additives.     

Action mechanism of antioxidation and anticorrosion and molecular design for perfluoropolyether fluid additives (I)

The combination energy and chemical adsorption energy of N-substituted perfluoropoly-alkyletherphenylamide (PFPEA) additive to perfluoropolyalkylether oxygen radical (R_fO.) and to Fe atom have been calculated by quantum chemical methods. Structural characteristics, action mechanism, property of donating-accepting electron and substituent effect for antioxidant and anticorrosive additive are investigated. It is found that HOMO of the additives is a π-molecular orbital with lone pair electron of heteroatom. The HOMO of PFPEA additive reacts with LUMO of Fe atom to result in chemical adsorption. The LUMO of additive can interact with the SOMO of R_fO. and accept electron of R_fO. to form stable addition product. The additives have the property of donating-accepting electron. The electron-releasing group, particularly, the phenyl group, introduced to N atom of phenylamide can increase the combination energy and chemical adsorption energy, and enhance the antioxidant and anticorrosive efficiency. The research achievements can provide useful information for the designing of new antioxidant and anticorrosive additive. Based on the calculated results, antioxidant and anticorrosive efficiency can be predicted roughly as the following order: compounds III>II>I>IV>V.     

Award for service Professor Jean-Marie Lehn

Chronicle

Award for service Professor Jean-Marie Lehn     

Approaches to Carbocyclic Sialidase Inhibitors Invited Review

 The crucial role played by carbohydrates in many physiological processes has made this class of compounds an interesting target for drug design. Consequently mimicking carbohydrates has been one of the most rapidly growing fields in synthetic organic chemistry in recent years, and particularly intense focus has been devoted to sialic acids and sialic acid metabolizing enzymes, including sialidases. Inhibition of the latter enzyme from influenza virus can be regarded as one of the most successful examples of structure-based drug design and high affinity inhibitors based on neuraminic acid have been developed. There is an ongoing search for inhibitors with improved physicochemical properties and among them, carbocyclic systems, where the ring oxygen of the carbohydrate is replaced by carbon, have become the center of interest. This review intends to give a brief overview over the structures and synthetic approaches which surfaced in the last decade.     

DNA microarray synthesis by using PDMS molecular stamp (II) Oligonucleotide on-chip synthesis using PDMS stamp

Based on the standard phosphoramidites chemistry protocol, two oligonucleotides synthetic routes were studied by contact stamping reactants to a modified glass slide. Route A was a contact coupling reaction, in which a nucleoside monomer was transferred and coupled to reactive groups (OH) on a substrate by spreading the nucleoside activated with tetrazole on a polydimethylsiloxane (PDMS) stamp. Route B was a contact detritylation, in which one nucleoside was fixed on the desired synthesis regions where dimethoxytrityl (DMT) protecting groups on the 5’-hydroxyl of the support-bound nucleoside were removed by stamping trichloroacetic acid (TCA) distributed on features on a PDMS stamp. Experiments showed that the synthetic yield and the reaction speed of route A were higher than those of route B. It was shown that 20 mer oligonucleotide arrays immobilized on the glass slide were successfully synthesized using the PDMS stamps, and the coupling efficiency showed no difference between the PDMS stamping and the conventional synthesis methods.     

Molecular electronegativity in density functional theory(VIII) Charge polarization modes in a closed system

Based on the density functional theory and the atom-bond electronegativity equalization model (ABEEM), a method is proposed to construct the softness matrix and to obtain the electron population normal modes (PNMs) for a closed system. Using this method the information about the bond charge polarization in a molecule can be obtained easily. The test calculation shows that the PNM obtained by this method includes all the modes about the bond charge polarization explicitly. And the bond charge polarization mode characterized by the biggest eigenvalue, which is the softest one of all modes related with chemical bonds, can describe the charge polarization process in a molecule as exquisitely as the correspondingab initio method.     

Trimethylsilyl-substituted diazoalkanes : I. Trimethylsilyldiazomethane

Trimethylsilyldiazomethane was prepared by the action of aqueous KOH on nitroso-N-(trimethylsilylmethyl)urea. The spectroscopic properties of this stable, greenish-yellow liquid which can be isolated by gas chromatography are discussed. Its reaction with acetic acid gives the expected CH₃CO₂CH₂SiMe₃ in addition to SiC cleavage products, CH₃CO₂CH₃ and CH₃CO₂SiMe₃. Products of the 1,3-dipolar addition of Me₃SiCHN₂ to activated olefins were not very stable, and only the adduct with acrylonitrile was isolated as a pure material Trimethylsilyldiazomethane undergoes Me₃SiCH transfer to olefins, giving trimethylsilyl-substituted cyclopropanes, in the presence of CuCI in benzene, but other products are formed as well. Thus such a reaction with cyciohexenegave anti-7-trimethylsilylnorcarane (65%), syn-7-trimethylsilylnorcarane (7%), cis- and trans-l,2-bis(trimethylsilyl)ethylene (9% and 13%, respectively), and an unidentified Me₃SiCH trimer (2.3%).     

Interactions of ammonium nitrate with different additives Thermodynamic analysis

In order to elucidate the influence of Ca and Mg carbonates with or without the presence of boron, manganese and copper compounds on the thermal stability of ammonium nitrate (AN), thermodynamic analysis of different reactions between AN and additives was carried out. Temperature dependency of Gibbs free energy changes ∆G _T and equilibrium composition of reaction products were calculated for a set of reactions using the HSC software. Main solid compounds that can form in the systems of AN and carbonates, were Ca(NO₃)₂ and Mg(NO₃)₂, Ca(OH)₂ and Mg(OH)₂, CaO₂ and MgO₂, CaO and MgO, and N-containing gaseous compounds NO, N₂O and NO₂. As a result of H₃BO₃, MnO₂ and CuSO₄ addition, the content of CuO, Cu₂O and MnO as solids and SO₂, SO₃ and HBO as gaseous reaction products reached the same level. Thereby, their equilibrium concentrations did not depend on the carbonate origin of CaCO₃, MgCO₃ or CaMg(CO₃)₂. Small amount of CuSO₄, H₃BO₃ or MnO₂ additive (0.01–0.05 mol) in the system, practically, did not influence the temperature dependencies of ∆G _T of the reactions between AN and CaCO₃ or CaMg(CO₃)₂. The influence of additives taken in the larger amount (0.5 mol) was evident and, depending on the additive and reaction, shifted their proceeding temperatures in either direction by more than 300–400 K.     

Mono and dinuclear Pd(II) complexes with pyrazole and imidazole-type ligands Synthesis, characterization and thermal behaviour

The cyanate-bridged cyclopalladated compound [Pd(C²,N-dmba)(μ-NCO)]₂ (dmba=N,N-dimethylbenzylamine) reacts in acetone with pyrazole (pz), 3,5-dimethylpyrazole (dmpz), imidazole (imz) and 2-methylimidazole (mimz) to give [Pd₂(C²,N-dmba)₂(μ-NCO)(μ-pz)] (1), [Pd₂(C²,N-dmba)₂(μ-NCO)(μ-dmpz)] (2), [Pd(C²,N-dmba)(NCO)(imz)] (3) and [Pd(C²,N-dmba)(NCO)(mimz)] (4), respectively. The compounds were characterized by elemental analysis, IR spectroscopy and TG. The thermal decomposition of the compounds occurs in three consecutive steps and the final decomposition products were identified as Pd(0) by X-ray powder diffraction. The thermal stability order of the complexes is 2>3>1>4.     

Interactions between Ni ions and tetrapeptides containing (Asp/Lys)HisGly(l/d)His sequence

A series of linear tetrapeptides containing two histidyl residues in positions 2 and 4 with different chirality: DHGH, DHG(d-His), KHGH, KHG(d-His), Ac-DHGH-NH₂, Ac-DHG(d-His)-NH₂, Ac-KHGH-NH₂, and Ac-KHG(d-His)-NH₂ were synthesized, characterized and their binding properties towards Ni²⁺ were investigated. To establish the stoichiometry and the stability of the resulting Ni²⁺ complexes, potentiometric titrations were carried out. The coordination mode of the complexes formed was investigated by performing extensive spectroscopic analyses (UV–Vis, CD) in strict correlation with the potentiometric results. The effects of the nature of the first amino acid (Lys versus Asp) and of the N-terminal amino group acetylation were determined. A careful comparison of the Ni²⁺ coordination abilities of the linear peptides provides a specific insight into the impact of the chirality of the C-terminal histidine residue (His⁴) on the metal binding properties.     

Synthesis of l,l-puromycin

l,l-Puromycin, a diastereomer of the natural peptidyl nucleoside antibiotic puromycin, has been synthesized from l-xylose in 13 steps.     

Stereocontrolled (E,Z and erythro, threo) synthesis of ⊙-hydroxyallylic sulphides

All four isomers of substituted 3-alkylthio-4-hydroxybutenes have been synthesised: both the geometry of the double bond and the relative stereochemistry of the two chiral centres are controlled.